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  • C12N9/00—Enzymes; Proenzymes; Compositions thereof; Processes for preparing, activating, inhibiting, separating or purifying enzymes
  • C12N9/14—Hydrolases (3)
  • C12N9/16—Hydrolases (3) acting on ester bonds (3.1)
  • C12N9/22—Ribonucleases [RNase]; Deoxyribonucleases [DNase]
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K38/00—Medicinal preparations containing peptides
  • A61K38/16—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
  • A61K38/43—Enzymes; Proenzymes; Derivatives thereof
  • A61K38/46—Hydrolases (3)
  • A61K38/465—Hydrolases (3) acting on ester bonds (3.1), e.g. lipases, ribonucleases
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  • C07K—PEPTIDES
  • C07K14/00—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
  • C07K14/195—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from bacteria
  • C07K14/315—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from bacteria from Streptococcus (G), e.g. Enterococci
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  • C12N15/00—Mutation or genetic engineering; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification; Use of hosts therefor
  • C12N15/01—Preparation of mutants without inserting foreign genetic material therein; Screening processes therefor
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  • C12N15/00—Mutation or genetic engineering; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification; Use of hosts therefor
  • C12N15/09—Recombinant DNA-technology
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  • C12N15/00—Mutation or genetic engineering; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification; Use of hosts therefor
  • C12N15/09—Recombinant DNA-technology
  • C12N15/87—Introduction of foreign genetic material using processes not otherwise provided for, e.g. co-transformation
  • C12N15/90—Stable introduction of foreign DNA into chromosome
  • C12N15/902—Stable introduction of foreign DNA into chromosome using homologous recombination
  • C12N15/907—Stable introduction of foreign DNA into chromosome using homologous recombination in mammalian cells
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  • C12N9/00—Enzymes; Proenzymes; Compositions thereof; Processes for preparing, activating, inhibiting, separating or purifying enzymes
  • C12N9/10—Transferases (2.)
  • C12N9/12—Transferases (2.) transferring phosphorus containing groups, e.g. kinases (2.7)
  • C12N9/1241—Nucleotidyltransferases (2.7.7)
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K38/00—Medicinal preparations containing peptides
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K47/00—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07K—PEPTIDES
  • C07K2319/00—Fusion polypeptide
  • C07K2319/01—Fusion polypeptide containing a localisation/targetting motif
  • C07K2319/09—Fusion polypeptide containing a localisation/targetting motif containing a nuclear localisation signal
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07K—PEPTIDES
  • C07K2319/00—Fusion polypeptide
  • C07K2319/80—Fusion polypeptide containing a DNA binding domain, e.g. Lacl or Tet-repressor

Definitions

• Site-specific endonucleases theoretically allow for the targeted manipulation of a single site within a genome and are useful in the context of gene targeting for therapeutic and research applications.
• site-specific endonucleases In a variety of organisms, including mammals, site-specific endonucleases have been used for genome engineering by stimulating either non-homologous end joining or homologous recombination.
• site-specific nucleases In addition to providing powerful research tools, site-specific nucleases also have potential as gene therapy agents, and two site-specific endonucleases have recently entered clinical trials:(l) CCR5-2246, targeting a human CCR-5 allele as part of an anti-HIV therapeutic approach (NCT00842634, NCT01044654,
• NCT01252641 NCT01252641
• VF24684 targeting the human VEGF-A promoter as part of an anticancer therapeutic approach
• RNA-guided nucleases such as Cas9.
• SSRs site-specific recombinases
• These enzymes perform rearrangements of DNA segments by recognizing and binding to short DNA sequences, at which they cleave the DNA backbone, exchange the two DNA helices involved and rejoin the DNA strands. Such rearrangements allow for the targeted insertion, inversion, excision, or translocation of DNA segments.
• Some aspects of this disclosure are based on the recognition that the reported toxicity of some engineered site-specific endonucleases is based on off-target DNA cleavage.
• certain aspects described herein relate to the discovery that increasing the number of sequences (e.g., having a nuclease bind at more than one site at a desired target), and/or splitting the activities (e.g., target binding and target cleaving) of a nuclease between two or more proteins, will increase the specificity of a nuclease and thereby decrease the likelihood of off-target effects.
• aspects of this disclosure provide strategies, compositions, systems, and methods to improve the specificity of site-specific nucleases, in particular, RNA -programmable endonucleases, such as Cas9 endonuclease. Certain aspects of this disclosure provide variants of Cas9 endonuclease engineered to have improved specificity.
• RNA-programmable (nuclease-inactivated) nucleases or RNA-binding domains thereof
• a recombinase domain provide novel recombinases theoretically capable of binding and recombining DNA at any site chosen, e.g., by a practitioner (e.g., sites specified by guide RNAs (gRNAs) that are engineered or selected according the sequence of the area to be recombined).
• gRNAs guide RNAs
• novel recombinases are therefore useful, inter alia, for the targeted insertion, deletion, inversion, translocation or other genomic modifications.
• methods of using these inventive recombinase fusion proteins e.g., for such targeted genomic manipulations.
• one embodiment of the disclosure provides fusion proteins and dimers thereof, for example, fusion proteins comprising two domains: (i) a nuclease- inactivated Cas9 domain; and (ii) a nuclease domain (e.g. , a monomer of the Fokl DNA cleavage domain). See e.g., Figures 1A, 6D.
• the fusion protein may further comprise a nuclear localization signal (NLS) domain, which signals for the fusion proteins to be transported into the nucleus of a cell.
• NLS nuclear localization signal
• one or more domains of the fusion proteins are separated by a linker.
• the linker is a non-peptidic linker.
• the linker is a peptide linker.
• the peptide linker may comprise an XTEN linker, an amino acid sequence comprising one or more repeats of the tri-peptide GGS, or any sequence as provided in Figure 12A.
• the fusion protein is encoded by a nucleotide sequence set forth as SEQ ID NO:9, SEQ ID NO: 10, SEQ ID NO: 11, or SEQ ID NO: 12, or a variant or fragment of any one of SEQ ID NO:9, SEQ ID NO: 10, SEQ ID NO: 11, or SEQ ID NO: 12.
• the nuclease- inactivated Cas9 domain is capable of binding a guide RNA (gRNA).
• gRNA guide RNA
• dimers of such fusion protein each comprising a gRNA binding two distinct regions of a target nucleic acid provides for improved specificity, for example as compared to monomeric RNA-guided nucleases comprising a single gRNA to direct binding to the target nucleic acid.
• methods for site- specific DNA cleavage using the inventive Cas9 variants typically comprise (a) contacting DNA with a fusion protein of the invention (e.g., a fusion protein comprising a nuclease-inactivated Cas9 domain and a Fokl DNA cleavage domain), wherein the inactive Cas9 domain binds a gRNA that hybridizes to a region of the DNA; (b) contacting the DNA with a second fusion protein (e.g., a fusion protein comprising a nuclease-inactivated Cas9 and Fokl DNA cleavage domain), wherein the inactive Cas9 domain of the second fusion protein binds a second gRNA that hybridizes to a second region of DNA; wherein the binding of the fusion proteins in steps (a) and (b) results in the dimerization of the nuclease domains of the fusion proteins, such that the DNA is
• the gRNAs of steps (a) and (b) hybridize to the same strand of the DNA, or the gRNAs of steps (a) and (b) hybridize to opposite strands of the DNA. In some embodiments, the gRNAs of steps (a) and (b) hybridize to regions of the DNA that are no more than 10, no more than 15, no more than 20, no more than 25, no more than 30, no more than 40, no more than 50, no more than 60, no more than 70, no more than 80, no more than 90, or no more than 100 base pairs apart. In some embodiments, the DNA is in a cell, for example, a eukaryotic cell or a prokaryotic cell, which may be in an individual, such as a human.
• a complex comprising a dimer of fusion proteins of the invention (e.g. , a dimer of a fusion protein comprising a nuclease-inactivated Cas9 and a Fokl DNA cleavage domain) are provided.
• the nuclease- inactivated Cas9 domain of each fusion protein of the dimer binds a single extended gRNA, such that one fusion protein of the dimer binds a portion of the gRNA, and the other fusion protein of the dimer binds another portion of the gRNA. See e.g., Figure IB.
• the gRNA is at least 50, at least 75, at least 100, at least 150, at least 200, at least 250, or at least 300 nucleotides in length.
• the regions of the extended gRNA that hybridize to a target nucleic acid comprise 15-25, 19-21, or 20 nucleotides.
• methods for site-specific DNA cleavage comprising contacting a DNA with a complex of two inventive fusion proteins bound to a single extended gRNA.
• the gRNA contains two portions that hybridize to two separate regions of the DNA to be cleaved; the complex binds the DNA as a result of the portions of the gRNA hybridizing to the two regions; and binding of the complex results in dimerization of the nuclease domains of the fusion proteins, such that the domains cleave the DNA in a region between the bound fusion proteins.
• the two portions of the gRNA hybridize to the same strand of the DNA.
• the two portions of the gRNA hybridize to opposing strands of the DNA. In some embodiments, the two portions of the gRNA hybridize to regions of the DNA that are no more 10, no more than 15, no more than 20, no more than 25, no more than 30, no more than 40, no more than 50, no more than 60, no more than 70, no more than 80, no more than 90, or no more than 100 base pairs apart.
• the DNA is in a cell, for example, a eukaryotic cell or a prokaryotic cell, which may be in an individual, such as a human.
• a protein comprising a gRNA binding domain of Cas9 but does not include a DNA cleavage domain.
• proteins comprising a DNA cleavage domain of Cas9, but not a gRNA binding domain are provided.
• a fusion protein comprising two domains: (i) a nuclease-inactivated Cas9 domain, and (ii) a gRNA binding domain of Cas9 are provided, for example, wherein domain (ii) does not include a DNA cleavage domain. See e.g.,, Figure 2B.
• fusion proteins comprising two domains: (i) a nuclease- inactivated Cas9 domain, and (ii) a DNA cleavage domain are provided, for example, wherein domain (ii) does not include a gRNA binding domain.
• a dimer comprises two halves of a split Cas9 protein, for example, (i) a protein comprising a gRNA binding domain of Cas9, but not a DNA cleavage domain, and (ii) a protein comprising a DNA cleavage domain of Cas9, but not a gRNA binding domain. See e.g., Figure 2A.
• a dimer comprises one half of a split Cas9 protein, and a fusion protein comprising the other half of the split Cas9 protein.
• such a dimer comprises (i) a protein comprising a gRNA binding domain of Cas9, but not a DNA cleavage domain, and (ii) a fusion protein comprising a nuclease-inactivated Cas9 and a DNA cleavage domain.
• the dimer comprises (i) a protein comprising a DNA cleavage domain of Cas9, but not a gRNA binding domain, and (ii) a fusion protein comprising a nuclease-inactivated Cas9 and a gRNA binding domain of Cas9.
• a dimer in some embodiments, comprises two fusion proteins, each fusion protein comprising a nuclease-inactivated Cas9 and one half of a split Cas9. See e.g.,, Figure 2C.
• a dimer comprises: (i) a fusion protein comprising a nuclease-inactivated Cas9 and a gRNA binding domain of Cas9, and (ii) a fusion protein comprising a nuclease-inactivated Cas9 and a DNA cleavage domain.
• any of the provided protein dimers is associated with one or more gRNA(s).
• such a method comprises contacting DNA with a protein dimer that comprises (i) a protein comprising a gRNA binding domain of Cas9, but not a DNA cleavage domain, and (ii) a protein comprising a DNA cleavage domain of Cas9, but not a gRNA binding domain, wherein the dimer binds a gRNA that hybridizes to a region of the DNA, and cleavage of the DNA occurs. See e.g., Figure 2A.
• the protein dimer used for site-specific DNA cleavage comprises (i) a protein comprising a gRNA binding domain of Cas9, but not a DNA cleavage domain, and (ii) a fusion protein comprising a nuclease-inactivated Cas9 and a DNA cleavage. See e.g., Figure 2B.
• the dimer used for site-specific DNA cleavage comprises (i) a protein comprising a DNA cleavage domain of Cas9, but not a gRNA binding domain, and (ii) a fusion protein comprising a nuclease-inactivated Cas9 and a gRNA binding domain of Cas9.
• the protein dimer binds two gRNAs that hybridize to two regions of the DNA, and cleavage of the DNA occurs. See e.g., Figure 2B.
• the two gRNAs hybridize to regions of the DNA that are no more than 10, no more than 15, no more than 20, no more than 25, no more than 30, no more than 40, no more than 50, no more than 60, no more than 70, no more than 80, no more than 90, or no more than 100 base pairs apart.
• the dimer used for site-specific DNA cleavage comprises two fusion proteins: (i) a fusion protein comprising a nuclease- inactivated Cas9 and a gRNA binding domain of Cas9, and (ii) a fusion protein comprising a nuclease-inactivated Cas9 and a DNA cleavage domain.
• the protein dimer binds three gRNAs that hybridize to three regions of the DNA, and cleavage of the DNA occurs. Having such an arrangement, e.g.
• targeting more than one region of a target nucleic acid increases the specificity of cleavage as compared to a nuclease binding a single region of a target nucleic acid.
• the three gRNAs hybridize to regions of the DNA that are no more than 10, no more than 15, no more than 20, no more than 25, no more than 30, no more than 40, no more than 50, no more than 60, no more than 70, no more than 80, no more than 90, or no more than 100 base pairs apart between the first and second, and the second and third regions.
• the DNA is in a cell, for example, a eukaryotic cell or a prokaryotic cell, which may be in an individual, such as a human.
• minimal Cas9 proteins are provided, for example, wherein the protein comprises N- and/or C-terminal truncations and retains RNA binding and DNA cleavage activity.
• the N-terminal truncation removes at least 5, at least 10, at least 15, at least 20, at least 25, at least 40, at least 40, at least 50, at least 75, at least 100, or at least 150 amino acids.
• the C- terminal truncation removes at least 5, at least 10, at least 15, at least 20, at least 25, at least 40, at least 40, at least 50, at least 75, at least 100, or at least 150 amino acids.
• the minimized Cas9 protein further comprises a bound gRNA.
• methods for site- specific DNA cleavage comprising contacting a DNA with minimized Cas9 protein:gRNA complex.
• dimers of Cas9 (or fragments thereof) wherein the dimer is coordinated through a single gRNA are provided.
• the single gRNA comprises at least two portions that (i) are each able to bind a Cas9 protein and (ii) each hybridize to a target nucleic acid sequence (e.g., DNA sequence).
• a target nucleic acid sequence e.g., DNA sequence
• the portions of the gRNA that hybridize to the target nucleic acid each comprise no more than 5, no more than 10, or no more than 15 nucleotides complementary to the target nucleic acid sequence.
• the portions of the gRNA that hybridize to the target nucleic acid are separated by a linker sequence.
• the linker sequence hybridizes to the target nucleic acid. See e.g., Figure 4.
• methods for site- specific DNA cleavage comprising contacting DNA with a dimer of Cas9 proteins coordinated through a single gRNA.
• the disclosure provides fusion proteins and dimers and tetramers thereof, for example, fusion proteins comprising two domains: (i) a nuclease-inactivated Cas9 domain; and (ii) a recombinase catalytic domain. See, e.g., Figure 5.
• the recombinase catalytic domain in some embodiments, is derived from the
• the nuclease-inactivated Cas9 domain is capable of binding a gRNA, e.g., to target the fusion protein to a target nucleic acid sequence.
• the fusion proteins may further comprise a nuclear localization signal (NLS) domain, which signals for the fusion proteins to be transported into the nucleus of a cell.
• NLS nuclear localization signal
• one or more domains of the fusion proteins are separated by a linker.
• the linker is a non-peptidic linker.
• the linker is a peptide linker.
• the peptide linker may comprise an XTEN linker, an amino acid sequence comprising one or more repeats of the tri-peptide GGS, or any sequence as provided in Figure 12A.
• the method is useful for recombining two separate DNA molecules, and comprises (a) contacting a first DNA with a first RNA-guided recombinase fusion protein, wherein the nuclease-inactivated Cas9 domain binds a first gRNA that hybridizes to a region of the first DNA; (b) contacting the first DNA with a second RNA-guided recombinase fusion protein, wherein the nuclease-inactivated Cas9 domain of the second fusion protein binds a second gRNA that hybridizes to a second region of the first DNA; (c) contacting a second DNA with a third RNA-guided recombinase fusion protein, wherein the nuclease- inactivated Cas9 domain of the third fusion protein
• the method comprises (a) contacting a DNA with a first RNA-guided recombinase fusion protein, wherein the nuclease-inactivated Cas9 domain binds a first gRNA that hybridizes to a region of the DNA; (b) contacting the DNA with a second RNA-guided recombinase fusion protein, wherein the nuclease-inactivated Cas9 domain of the second fusion protein binds a second gRNA that hybridizes to a second region of the DNA; (c) contacting the DNA with a third RNA-guided recombinase fusion protein, wherein the nuclease-inactivated Cas9 domain of the third fusion protein binds a third gRNA that hybridizes to a third region of the DNA; (d) contacting the DNA with a fourth RNA-guided recombinase fusion protein, wherein the nuclease-inactivated Cas9 domain of
• gRNAs hybridizing to the same DNA molecule hybridize to opposing strands of the DNA molecule.
• two gRNAs hybridize to one strand of the DNA, and the other two gRNAs hybridize to the opposing strand.
• the gRNAs hybridize to regions of their respective DNAs (e.g., on the same strand) that are no more than 10, no more than 15, no more than 20, no more than 25, no more than 30, no more than 40, no more than 50, no more than 60, no more than 70, no more than 80, no more than 90, or no more than 100 base pairs apart.
• the DNA is in a cell, for example, a eukaryotic cell or a prokaryotic cell, which may be in or obtained from an individual, such as a human.
• polynucleotides are provided, for example, that encode any of the Cas9 proteins described herein (e.g. , Cas9 variants, Cas9 dimers, Cas9 fusion proteins, Cas9 fragments, minimized Cas9 proteins, Cas9 variants without a cleavage domain, Cas9 variants without a gRNA domain, Cas9-recombinase fusions, etc.).
• polynucleotides encoding any of the gRNAs described herein are provided.
• polynucleotides encoding any inventive Cas9 protein described herein and any combination of gRNA(s) as described herein are provided.
• vectors that comprise a polynucleotide described herein are provided.
• vectors for recombinant protein expression comprising a polynucleotide encoding any of the Cas9 proteins and/or gRNAs described herein are provided.
• cells comprising genetic constructs for expressing any of the Cas9 proteins and/or gRNAs described herein are provided.
• kits are provided.
• kits comprising any of the Cas9 proteins and/or gRNAs described herein are provided.
• kits comprising any of the polynucleotides described herein, e.g., those encoding a Cas9 protein and/or gRNA, are provided.
• kits comprising a vector for recombinant protein expression, wherein the vectors comprise a polynucleotide encoding any of the Cas9 proteins and/or gRNAs described herein, are provided.
• kits comprising a cell comprising genetic constructs for expressing any of the Cas9 proteins and/or gRNAs described herein are provided.
• FIG. 1 is a schematic detailing certain embodiments of the invention.
• nuclease-inactivated Cas9 protein is fused to a monomer of the Fokl nuclease domain. Double-strand DNA-cleavage is achieved through dimerization of Fokl monomers at the target site and is dependent on the simultaneous binding of two distinct Cas9:gRNA complexes.
• B In this embodiment, an alternate configuration is provided, wherein two Cas9-FokI fusions are coordinated through the action of a single extended gRNA containing two distinct gRNA motifs.
• the gRNA motifs comprise regions that hybridize the target in distinct regions, as well as regions that bind each fusion protein.
• the extended gRNA may enhance cooperative binding and alter the specificity profile of the fusions.
• FIG. 2 is a schematic detailing certain embodiments of the invention.
• dimeric split Cas9 separates A) gRNA-binding ability from B) dsDNA cleavage. DNA cleavage occurs when both halves of the protein are co-localized to associate and refold into a nuclease-active state.
• nuclease- inactivated Cas9 mutant is fused to the A-half (or in some embodiments, the B-half) of the split Cas9 nuclease.
• nuclease-inactivated Cas9 mutant is fused to the A-half of the split Cas9 nuclease.
• a separate nuclease-inactivated Cas9 mutant is fused to the B-half of the split Cas9 nuclease.
• the split Cas9 halves can dimerize and bind a third gRNA target to become a fully active Cas9 nuclease that can cleave dsDNA.
• This split Cas9-pairing uses three distinct gRNA-binding Cas9 proteins to ensure the split nuclease- active Cas9 reassembles only on the correct target sequence. Any other DNA -binding domain in place of the inactive Cas9 (zinc fingers, TALE proteins, etc.) can be used to complete the reassembly of the split Cas9 nuclease.
• FIG. 3 shows schematically a minimal Cas9 protein that comprises the essential domains for Cas9 activity.
• Full-length Cas9 is a 4.1 kb gene which results in a protein of > 150 kDa. Specific deletions and/or truncations decrease the size of Cas9 without affecting its activity (e.g. , gRNA binding and DNA cleavage activity).
• the minimized Cas9 protein increases the efficacy of, for example,, delivery to cells using viral vectors such as AAV (accommodating sequences ⁇ ⁇ 4700 bp) or lentivirus (accommodating sequences ⁇ ⁇ 9 kb), or when pursuing multiplexed gRNA/Cas9 approaches.
• FIG 4 shows how two Cas9 proteins can be coordinated through the action of a single extended RNA containing two distinct gRNA motifs.
• Each gRNA targeting region is shortened, such that a single Cas9:gRNA unit cannot bind efficiently by itself.
• the normal 20 nt targeting sequence has been altered so that some portion (e.g., the 5' initial 10 nt) has been changed to some non-specific linker sequence, such as AAAAAAAAAA (SEQ ID NO: 13), with only 10 nt of the gRNA remaining to direct target binding (alternatively this 5' 10 nt is truncated entirely).
• This "low- affinity" gRNA unit exists as part of a tandem gRNA construct with a second, distinct low-affinity gRNA unit downstream, separated by a linker sequence.
• the linker comprises a target nucleic acid complementary sequence (e.g., as depicted by the linker region contacting the DNA target).
• FIG. 5 shows schematically, how Cas9-recombinase fusions can be coordinated through gRNAs to bind and recombine target DNAs at desired sequences (sites).
• A, B Nuclease-inactivated Cas9 (dCas9) protein is fused to a monomer of a recombinase domain (Rec). Site- specific recombination is achieved through dimerization (A) of the recombinase catalytic domain monomers at the target site, and then tetramerization (B) of two dimers assembled on separate Cas9-recombination sites.
• the fusion to dCas9:gRNA complexes determines the sequence identity of the flanking target sites while the recombinase catalytic domain determines the identity of the core sequence (the sequence between the two dCas9-binding sites).
• Recombination proceeds through strand cleavage, exchange, and re-ligation within the dCas9-recombinase tetramer complex.
• Figure 6 shows architectures of Cas9 and i3 ⁇ 4M-dCas9 fusion variants.
• Cas9 protein in complex with a guide RNA binds to target DNA.
• the S. pyogenes Cas9 protein recognizes the PAM sequence NGG, initiating unwinding of dsDNA and gRNA:DNA base pairing.
• B i3 ⁇ 4M-dCas9 fusion architectures tested. Four distinct configurations of NLS, Fokl nuclease, and dCas9 were assembled. Seventeen (17) protein linker variants were also tested.
• C gRNA target sites tested within GFP. Seven gRNA target sites were chosen to test i3 ⁇ 4M-dCas9 activity in an orientation in which the PAM is distal from the cleaved spacer sequence (orientation A).
• EmGFP (bp 326-415)
• Gl corresponds to SEQ ID NO:205
• G2 corresponds to SEQ ID NO:206
• G3 corresponds to SEQ ID NO:207
• G4 corresponds to SEQ ID NO:208
• G5" corresponds to SEQ ID NO:209
• G6 corresponds to SEQ ID NO:210
• G7 corresponds to SEQ ID NO:211.
• Figure 7 shows genomic DNA modification by fCas9, Cas9 nickase, and wild-type Cas9.
• A shows a graph depicting GFP disruption activity of fCas9, Cas9 nickase, or wild-type Cas9 with either no gRNA, or gRNA pairs of variable spacer length targeting the GFP gene in orientation A.
• (B) is an image of a gel showing Indel modification efficiency from PAGE analysis of a Surveyor cleavage assay of renatured target-site DNA amplified from cells treated with fCas9, Cas9 nickase, or wild-type Cas9 and two gRNAs spaced 14 bp apart targeting the GFP site (gRNAs G3 and G7; Figure 6C), each gRNA individually, or no gRNAs.
• the Indel modification percentage is shown below each lane for samples with modification above the detection limit (-2%).
• C-G show graphs depicting Indel modification efficiency for (C) two pairs of gRNAs spaced 14 or 25 bp apart targeting the GFP site, (D) one pair of gRNAs spaced 19 bp apart targeting the CLTA site, (E) one pair of gRNAs spaced 23 bp apart targeting the EMX site, (F) one pair of gRNAs spaced 16 bp apart targeting the HBB site, and (G) two pairs of gRNAs spaced 14 or 16 bp apart targeting the VEGF site.
• Error bars reflect standard error of the mean from three biological replicates performed on different days.
• Figure 8 shows the DNA modification specificity of fCas9, Cas9 nickase, and wild-type Cas9.
• A shows a graph depicting GFP gene disruption by wild-type Cas9, Cas9 nickase, and fCas9 using gRNA pairs in orientation A. High activity of fCas9 requires spacer lengths of -15 and 25 bp, roughly one DNA helical turn apart.
• B shows a graph depicting GFP gene disruption using gRNA pairs in orientation B. Cas9 nickase, but not fCas9, accepts either orientation of gRNA pairs.
• (C) shows a graph depicting GFP gene disruption by fCas9, but not Cas9 nickase or wild-type Cas9, which depends on the presence of two gRNAs.
• Four single gRNAs were tested along with three gRNA pairs of varying spacer length.
• gRNAs 1+5, and gRNAs 3+7, respectively In the presence of gRNA pairs in orientation A with spacer lengths of 14 or 25 bp (gRNAs 1+5, and gRNAs 3+7, respectively), fCas9 is active, but not when a gRNA pair with a 10-bp spacer (gRNAs 1+4) is used.
• “no treatment” refers to cells receiving no plasmid DNA.
• (D-F) show graphs depicting the indel mutation frequency from high- throughput DNA sequencing of amplified genomic on-target sites and off-target sites from human cells treated with fCas9, Cas9 nickase, or wild-type Cas9 and (D) two gRNAs spaced 19 bp apart targeting the CLTA site (gRNAs CI and C2), (E) two gRNAs spaced 23 bp apart targeting the EMX site (gRNAs El and E2), or (F, G) two gRNAs spaced 14 bp apart targeting the VEGF site (gRNAs VI and V2). (G) shows a graph depicting two in-depth trials to measure genome modification at VEGF off-target site 1.
• Trial 1 used 150 ng of genomic input DNA and > 8 x 10 5 sequence reads for each sample; trial 2 used 600 ng of genomic input DNA and > 23 x 10 5 sequence reads for each sample.
• D-G all significant (P value ⁇ 0.005 Fisher's Exact Test) indel frequencies are shown. P values are listed in Table 3.
• D-F each on- and off-target sample was sequenced once with > 10,000 sequences analyzed per on-target sample and an average of 76,260 sequences analyzed per off-target sample (Table 3).
• Seven gRNA target sites were chosen to test FokI-dCas9 candidate activity in an orientation in which the PAM is adjacent to the cleaved spacer sequence (orientation B). Together, these seven gRNAs enabled testing of FokI-dCas9 fusion variants across six spacer lengths ranging from 4 to 42 bp.
• EmGFP (bp 297-388)
• G8 corresponds to SEQ ID NO:213
• G9 corresponds to SEQ ID NO:214
• G10 corresponds to SEQ ID NO:215
• Gi l corresponds to SEQ ID NO:216
• G12 corresponds to SEQ ID NO:217
• G13 corresponds to SEQ ID NO:218
• G14 corresponds to SEQ ID NO:219.
• FIG. 10 shows a GFP disruption assay for measuring genomic DNA- modification activity.
• A depicts schematically a HEK293-derived cell line constitutively expressing a genomically integrated EmGFP gene used to test the activity of candidate Fokl- dCas9 fusion constructs. Co-transfection of these cells with appropriate nuclease and gRNA expression plasmids leads to dsDNA cleavage within the EmGFP coding sequence, stimulating error-prone NHEJ and generating indels that can disrupt the expression of GFP, leading to loss of cellular fluorescence. The fraction of cells displaying a loss of GFP fluorescence is then quantitated by flow cytometry.
• B shows typical epifluorescence microscopy images at 200x magnification of EmGFP-HEK293 cells before and after co- transfection with wild-type Cas9 and gRNA expression plasmids.
• FIG 11 shows a graph depicting the activities of FokI-dCas9 fusion candidates combined with gRNA pairs of different orientations and varying spacer lengths.
• the fusion architectures described in Figure 6B were tested for functionality by flow cytometry using the GFP loss-of-function reporter across all (A) orientation A gRNA spacers and (B) orientation B gRNA spacers ( Figure 6C and Figure 9).
• All FokI-dCas9 fusion data shown are the results of single trials. Wild- type Cas9 and Cas9 nickase data are the average of two replicates, while the 'no treatment' negative control data is the average of 6 replicates, with error bars representing one standard deviation.
• the grey dotted line across the Y-axis corresponds to the average of the 'no treatment' controls performed on the same day.
• the sequence shown as "(GGS)x3" corresponds to SEQ ID NO: 14.
• Figure 12 shows the optimization of protein linkers in NLS-FokI-dCas9.
• A shows a table of all linker variants tested. Wild-type Cas9 and Cas9 nickase were included for comparison. The initial active construct NLS-FokI-dCas9 with a (GGS) 3 (SEQ ID NO: 14) linker between Fokl and dCas9 was tested across a range of alternate linkers. The final choice of linkers for fCas9 is highlighted.
• (B) shows a graph depicting the activity of FokI-dCas9 fusions with linker variants. Each variant was tested across a range of spacer lengths from 5 to 43 bp using gRNA pair orientation A.
• NLS-FokI-dCas9 variant L8 showed the best activity, approaching the activity of Cas9 nickase.
• Variants L4 through L9 show peak activity with 14- and 25-bp spacer lengths, suggesting two optimal spacer lengths roughly one helical turn of dsDNA apart.
• the sequences shown in (A) are identified as follows: GGSGGSGGS corresponds to SEQ ID NO: 14; GGSGGSGGSGGSGGSGGS corresponds to SEQ ID NO: 15; MKIIEQLPSA corresponds to SEQ ID NO:22;
• VRHKLKRVGS corresponds to SEQ ID NO:23; VPFLLEPDNINGKTC corresponds to SEQ ID NO: 19; GHGTGSTGSGSS corresponds to SEQ ID NO:24; MSRPDPA corresponds to SEQ ID NO:25; GSAGSAAGSGEF corresponds to SEQ ID NO:20; SGSETPGTSESA corresponds to SEQ ID NO: 17; SGSETPGTSESATPES corresponds to SEQ ID NO: 16; SGSETPGTSESATPEGGSGGS corresponds to SEQ ID NO: 18; GGSM corresponds to SEQ ID NO:301; and SIVAQLSRPDPA corresponds to SEQ ID NO:21.
• Figure 13 shows target DNA sequences in endogenous human EMX, VEGF,
• CLTA, and HBB genes The gRNA target sites tested within endogenous human EMX, VEGF, CLTA, and HBB genes are shown. Thirteen gRNA target sites were chosen to test the activity of the optimized fCas9 fusion in an orientation in which the PAM is distal from the cleaved spacer sequence (orientation A). Together, these 13 gRNAs enabled testing of fCas9 fusion variants across eight spacer lengths ranging from 5 to 47 bp.
• Figure 14 shows graphs depicting spacer length preference of genomic DNA modification by fCas9, Cas9 nickase, and wild-type Cas9. Indel modification efficiency for (A) pairs of gRNAs targeting the GFP site, (B) pairs of gRNAs targeting the CLTA site, (C) pairs of gRNAs targeting the EMX site (D) pairs of gRNAs targeting the HBB site, and (E) pairs of gRNAs targeting the VEGF site. Error bars reflect standard error of the mean from three biological replicates performed on different days.
• Figure 15 shows graphs depicting the efficiency of genomic DNA
• Indel modification efficiency from a Surveyor assay of renatured target-site DNA amplified from a population of cells treated with fCas9, Cas9 nickase, or wild-type Cas9 and two target site gRNAs.
• Figure 16 shows the ability of fCas9, Cas9 nickase, and wild-type Cas9 to modify genomic DNA in the presence of a single gRNA.
• A shows images of gels depicting Surveyor assay of a genomic GFP target from DNA of cells treated with the indicated combination of Cas9 protein and gRNA(s).
• Single gRNAs do not induce genome modification at a detectable level ( ⁇ 2% modification) for both fCas9 and Cas9 nickase. Wild-type Cas9 effectively modifies the GFP target for all tested single and paired gRNAs.
• FIG. 1 shows a graph depicting the results from sequencing GFP on-target sites amplified from 150 ng genomic DNA isolated from human cells treated with a plasmid expressing either wild-type Cas9, Cas9 nickase, or fCas9 and either a single plasmid expressing a single gRNAs (Gl, G3, G5 or G7), or two plasmids each expressing a different gRNA (G1+G5, or G3+G7).
• transfection and sequencing were performed in triplicate as above without any gRNA expression plasmids. Error bars represent s.d. Sequences with more than one insertion or deletion at the GFP target site (the start of the Gl binding site to the end of the G7 binding site) were considered indels. Indel percentages were calculated by dividing the number of indels by total number of sequences. While wild-type Cas9 produced indels across all gRNA treatments, fCas9 and Cas9 nickase produced indels efficiently (> 1%) only when paired gRNAs were present. Indels induced by fCas9 and single gRNAs were not detected above the no-gRNA control, while Cas9 nickase and single gRNAs modified the target GFP sequence at an average rate of 0.12%.
• Figure 17 shows a graph depicting how fCas9 indel frequency of genomic targets reflects gRNA pair spacer length preference.
• the graph shows the relationship between spacer length (number of bp between two gRNAs) and the indel modification efficiency of fCas9 normalized to the indel modification efficiency of the same gRNAs co- expressed with wild-type Cas9 nuclease.
• Colored triangles below the X-axis denote spacer lengths that were tested but which yielded no detectable indels for the indicated target gene.
• Figure 18 shows modifications induced by Cas9 nuclease, Cas9 nickases, or fCas9 nucleases at endogenous loci.
• A shows examples of modified sequences at the VEGF on-target site with wild-type Cas9 nuclease, Cas9 nickases, or fCas9 nucleases and a single plasmid expressing two gRNAs targeting the VEGF on-target site (gRNA VI and gRNA V2).
• the unmodified genomic site is the first sequence, followed by the top eight sequences containing deletions. The numbers before each sequence indicate sequencing counts.
• the gRNA target sites are bold and capitalized.
• (B) is an identical analysis as in (A) for VEGF off-target site lVEG_Offl.
• (C) shows the potential binding mode of two gRNAs to VEGF off-target site 1. The top strand is bound in a canonical mode, while the bottom strand binds the second gRNA, gRNA V2, through gRNA:DNA base pairing that includes G:U base pairs.
• sequences shown in (A) are identified, top to bottom, as follows: SEQ ID NO:243; SEQ ID NO:244; SEQ ID NO:245; SEQ ID NO:246; SEQ ID NO:247; SEQ ID NO:248; SEQ ID NO:249; SEQ ID NO:250; SEQ ID NO:251; SEQ ID NO:252; SEQ ID NO:253; SEQ ID NO:254; SEQ ID NO:255; SEQ ID NO:256; SEQ ID NO:257; SEQ ID NO:258; SEQ ID NO:259; SEQ ID NO:260; SEQ ID NO:261; SEQ ID NO:262; SEQ ID NO:263; SEQ ID NO:264; SEQ ID NO:265; SEQ ID NO:266; SEQ ID NO:267; SEQ ID NO:268; and SEQ ID NO:269.
• sequences shown in (B) are identified, top to bottom, as follows: SEQ ID NO:270; SEQ ID NO:271; SEQ ID NO:272; SEQ ID NO:273; SEQ ID NO:274; SEQ ID NO:275; SEQ ID NO:276; SEQ ID NO:277; SEQ ID NO:278; SEQ ID NO:279; SEQ ID NO:280; SEQ ID NO:281; SEQ ID NO:282; SEQ ID NO:283; SEQ ID NO:284; SEQ ID NO:285; SEQ ID NO:286; SEQ ID NO:287; SEQ ID NO:288; SEQ ID NO:289; SEQ ID NO:290; SEQ ID NO:291 ; SEQ ID NO:292; SEQ ID NO:293; SEQ ID NO:294; SEQ ID NO:295; and SEQ ID NO:296.
• the sequences shown in (C) are identified, top to bottom, as follows: SEQ ID
• Figure 19 shows the target DNA sequences in a genomic CCR5 gene.
• gRNA target sites were identified for testing Cas9 variant (e.g. , FokI-dCas9) activity in an orientation in which the PAM is adjacent to the cleaved spacer sequence (orientation A).
• B Six gRNA target sites were identified for testing Cas9 variant (e.g., FokI-dCas9) activity in an orientation in which the PAM is adjacent to the cleaved spacer sequence (orientation B).
• these fourteen gRNAs enable testing of Cas9 fusion variants across spacer lengths ranging from 0 to 74 bp.
• sequences shown in (A) are identified as follows: "CRA” corresponds to SEQ ID NO:302; "CRA-1” corresponds to SEQ ID NO:303; “CRA-2” corresponds to SEQ ID NO:304; “CRA-3” corresponds to SEQ ID NO:305; "CRA-4" corresponds to SEQ ID NO:306; "CRA-5" corresponds to SEQ ID NO:307; “CRA-6” corresponds to SEQ ID NO:308; “CRA-7” corresponds to SEQ ID NO:309; and "CRA-8” corresponds to SEQ ID NO:310.
• the sequences shown in (B) are identified as follows:
• CB corresponds to SEQ ID NO:311 ;
• CB-1 corresponds to SEQ ID NO:312;
• CB-2 corresponds to SEQ ID NO:313;
• CB-3 corresponds to SEQ ID NO:314;
• CB-4"
• Figure 20 depicts a vector map detailing an exemplary plasmid containing a
• Fokl-dCas9 (fCas9) construct Fokl-dCas9 (fCas9) construct.
• Cas9 or “Cas9 nuclease” refers to an RNA-guided nuclease comprising a Cas9 protein, or a fragment thereof (e.g. , a protein comprising an active or inactive DNA cleavage domain of Cas9, and/or the gRNA binding domain of Cas9).
• a Cas9 nuclease is also referred to sometimes as a casnl nuclease or a CRISPR (clustered regularly interspaced short palindromic repeat)-associated nuclease.
• CRISPR is an adaptive immune system that provides protection against mobile genetic elements (viruses, transposable elements and conjugative plasmids).
• CRISPR clusters contain spacers, sequences
• CRISPR clusters are transcribed and processed into CRISPR RNA (crRNA).
• crRNA CRISPR RNA
• tracrRNA trans-encoded small RNA
• rnc endogenous ribonuclease 3
• Cas9 protein The tracrRNA serves as a guide for ribonuclease 3-aided processing of pre-crRNA.
• Cas9/crRNA/tracrRNA endonucleolytically cleaves linear or circular dsDNA target complementary to the spacer.
• sgRNA single guide RNAs
• gNRA single guide RNAs
• Cas9 recognizes a short motif in the CRISPR repeat sequences (the PAM or protospacer adjacent motif) to help distinguish self versus non-self.
• Cas9 nuclease sequences and structures are well known to those of skill in the art (see, e.g., "Complete genome sequence of an Ml strain of Streptococcus pyogenes.” Ferretti et al., J.J., McShan W.M., Ajdic D.J., Savic D.J., Savic G., Lyon K., Primeaux C, Sezate S., Suvorov A.N., Kenton S., Lai H.S., Lin S.P., Qian Y., Jia H.G., Najar F.Z., Ren Q., Zhu H., Song L., White J., Yuan X., Clifton S.W., Roe B.A., McLaughlin R.E., Proc.
• Cas9 orthologs have been described in various species, including, but not limited to, S. pyogenes and S. thermophilus . Additional suitable Cas9 nucleases and sequences will be apparent to those of skill in the art based on this disclosure, and such Cas9 nucleases and sequences include Cas9 sequences from the organisms and loci disclosed in Chylinski, Rhun, and Charpentier, "The tracrRNA and Cas9 families of type II CRISPR-Cas immunity systems" (2013) RNA Biology 10:5, 726-737; the entire contents of which are incorporated herein by reference.
• a Cas9 nuclease has an inactive ⁇ e.g., an inactivated) DNA cleavage domain.
• a nuclease-inactivated Cas9 protein may interchangeably be referred to as a "dCas9" protein (for nuclease "dead” Cas9).
• dCas9 corresponds to, or comprises in part or in whole, the amino acid set forth as SEQ ID NO:5, below.
• variants of dCas9 e.g., variants of SEQ ID NO:5 are provided.
• variants having mutations other than D10A and H840A are provided, which e.g., result in nuclease inactivated Cas9 (dCas9).
• Such mutations include other amino acid substitutions at D10 and H840, or other substitutions within the nuclease domains of Cas9 (e.g., substitutions in the HNH nuclease subdomain and/or the RuvCl subdomain).
• variants or homologues of dCas9 are provided which are at least about 70% identical, at least about 80% identical, at least about 90% identical, at least about 95% identical, at least about 98% identical, at least about 99% identical, at least about 99.5% identical, or at least about 99.9% to SEQ ID NO:5.
• variants of dCas9 are provided having amino acid sequences which are shorter, or longer than SEQ ID NO:5, by about 5 amino acids, by about 10 amino acids, by about 15 amino acids, by about 20 amino acids, by about 25 amino acids, by about 30 amino acids, by about 40 amino acids, by about 50 amino acids, by about 75 amino acids, by about 100 amino acids or more.
• Methods for generating a Cas9 protein (or a fragment thereof) having an inactive DNA cleavage domain are known (See, e.g., the Examples; and Jinek et ah, Science. 337:816-821(2012); Qi et al, "Repurposing CRISPR as an RNA-Guided Platform for Sequence-Specific Control of Gene Expression” (2013) Cell. 28;152(5): 1173-83, the entire contents of each of which are incorporated herein by reference).
• the DNA cleavage domain of Cas9 is known to include two subdomains, the HNH nuclease subdomain and the RuvCl subdomain.
• the HNH subdomain cleaves the strand complementary to the gRNA, whereas the RuvCl subdomain cleaves the non-complementary strand. Mutations within these subdomains can silence the nuclease activity of Cas9. For example, the mutations DIOA and H840A completely inactivate the nuclease activity of S. pyogenes Cas9 (See e.g., the Examples; and Jinek et ah, Science. 337:816-821(2012); Qi et ah, Cell.
• proteins comprising fragments of Cas9 are provided.
• a protein comprises one of two Cas9 domains: (1) the gRNA binding domain of Cas9; or (2) the DNA cleavage domain of Cas9.
• proteins comprising Cas9 or fragments thereof are referred to as "Cas9 variants.”
• a Cas9 variant shares homology to Cas9, or a fragment thereof.
• a Cas9 variant is at least about 70% identical, at least about 80% identical, at least about 90% identical, at least about 95% identical, at least about 98% identical, at least about 99% identical, at least about 99.5% identical, or at least about 99.9% to wild type Cas9.
• the Cas9 variant comprises a fragment of Cas9 ⁇ e.g., a gRNA binding domain or a DNA-cleavage domain), such that the fragment is at least about 70% identical, at least about 80% identical, at least about 90% identical, at least about 95% identical, at least about 98% identical, at least about 99% identical, at least about 99.5% identical, or at least about 99.9% to the corresponding fragment of wild type Cas9.
• wild type Cas9 corresponds to Cas9 from Streptococcus pyogenes (NCBI Reference Sequence: NC_017053.1, SEQ ID NO: l (nucleotide); SEQ ID NO:2 (amino acid)).
• wild type Cas9 corresponds to, or comprises, SEQ ID NO:2
• SEQ ID NO:3 nucleotide
• SEQ ID NO:4 amino acid
• Cas9 refers to Cas9 from: Corynebacterium ulcerous
• NCBI Refs NC_015683.1, NC_017317.1
• Corynebacterium diphtheria NCBI Refs:
• NCBI Ref NC_017861.1
• Spiroplasma taiwanense NCBI Ref: NC_021846.1
• Streptococcus iniae NCBI Ref: NC_021314.1
• Belliella baltica NCBI Ref: NC_018010.1
• Psychroflexus torquisl NCBI Ref: NC_018721.1
• Streptococcus thermophilus NCBI Ref: YP_820832.1
• Listeria innocua NCBI Ref: NP_472073.1
• Campylobacter jejuni NCBI Ref: YP_002344900.1
• ox Neisseria, meningitidis NCBI Ref: YP_002342100.1
• conjugating refers to an association of two entities, for example, of two molecules such as two proteins, two domains ⁇ e.g., a binding domain and a cleavage domain), or a protein and an agent, e.g., a protein binding domain and a small molecule.
• the association is between a protein ⁇ e.g., RNA-programmable nuclease) and a nucleic acid ⁇ e.g., a guide RNA).
• the association can be, for example, via a direct or indirect ⁇ e.g., via a linker) covalent linkage. In some embodiments, the association is covalent.
• two molecules are conjugated via a linker connecting both molecules.
• the two proteins may be conjugated via a polypeptide linker, e.g., an amino acid sequence connecting the C-terminus of one protein to the N-terminus of the other protein.
• a polypeptide linker e.g., an amino acid sequence connecting the C-terminus of one protein to the N-terminus of the other protein.
• a consensus sequence is determined by sequence alignment in which similar sequences are compared to each other and similar sequence motifs are calculated.
• a consensus sequence of a nuclease target site may, in some embodiments, be the sequence most frequently bound, or bound with the highest affinity, by a given nuclease.
• a consensus sequence of a recombinase target site may, in some embodiments, be the sequence most frequently bound, or bound with the highest affinity, by a given recombinase.
• engineered refers to a protein molecule, a nucleic acid, complex, substance, or entity that has been designed, produced, prepared, synthesized, and/or manufactured by a human. Accordingly, an engineered product is a product that does not occur in nature.
• an effective amount refers to an amount of a biologically active agent that is sufficient to elicit a desired biological response.
• an effective amount of a nuclease may refer to the amount of the nuclease that is sufficient to induce cleavage of a target site specifically bound and cleaved by the nuclease.
• an effective amount of a recombinase may refer to the amount of the recombinase that is sufficient to induce recombination at a target site specifically bound and recombined by the recombinase.
• the effective amount of an agent e.g.
• a nuclease, a recombinase, a hybrid protein, a fusion protein, a protein dimer, a complex of a protein (or protein dimer) and a polynucleotide, or a polynucleotide may vary depending on various factors as, for example, on the desired biological response, the specific allele, genome, target site, cell, or tissue being targeted, and the agent being used.
• homologous is an art-understood term that refers to nucleic acids or polypeptides that are highly related at the level of nucleotide and/or amino acid sequence. Nucleic acids or polypeptides that are homologous to each other are termed "homologues.” Homology between two sequences can be determined by sequence alignment methods known to those of skill in the art. In accordance with the invention, two sequences are considered to be homologous if they are at least about 50-60% identical, e.g.
• residues e.g., amino acid residues
• share identical residues e.g., amino acid residues
• linker refers to a chemical group or a molecule linking two adjacent molecules or moieties, e.g., a binding domain (e.g., dCas9) and a cleavage domain of a nuclease (e.g., Fokl).
• a linker joins a nuclear localization signal (NLS) domain to another protein (e.g., a Cas9 protein or a nuclease or recombinase or a fusion thereof).
• a linker joins a gRNA binding domain of an RNA-programmable nuclease and the catalytic domain of a recombinase.
• a linker joins a dCas9 and a recombinase.
• the linker is positioned between, or flanked by, two groups, molecules, or other moieties and connected to each one via a covalent bond, thus connecting the two.
• the linker is an amino acid or a plurality of amino acids (e.g., a peptide or protein).
• the linker is an organic molecule, group, polymer, or chemical moiety.
• the linker is a peptide linker.
• the peptide linker is any stretch of amino acids having at least 1, at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 15, at least 20, at least 25, at least 30, at least 40, at least 50, or more amino acids.
• the peptide linker comprises repeats of the tri-peptide Gly-Gly-Ser, e.g., comprising the sequence (GGS) n , wherein n represents at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more repeats.
• the linker comprises the sequence (GGS) 6 (SEQ ID NO: 15).
• the peptide linker is the 16 residue "XTEN" linker, or a variant thereof (See, e.g., the Examples; and Schellenberger et al. A recombinant polypeptide extends the in vivo half-life of peptides and proteins in a tunable manner. Nat. Biotechnol. 27, 1186-1190 (2009)).
• XTEN 16 residue "XTEN” linker
• the XTEN linker comprises the sequence SGSETPGTSESATPES (SEQ ID NO: 16), SGSETPGTSESA (SEQ ID NO: 17), or SGSETPGTSESATPEGGSGGS (SEQ ID NO: 18).
• the peptide linker is any linker as provided in Figure 12A, for example, one or more selected from VPFLLEPDNINGKTC (SEQ ID NO: 19),
• GSAGSAAGSGEF SEQ ID NO:20
• SIVAQLSRPDPA SEQ ID NO:21
• MKIIEQLPSA SEQ ID NO:22
• VRHKLKRVGS SEQ ID NO:23
• GHGTGSTGSGSS SEQ ID NO:24
• MSRPDPA SEQ ID NO:25
• GGSM SEQ ID NO:301
• Mutations are typically described herein by identifying the original residue followed by the position of the residue within the sequence and by the identity of the newly substituted residue.
• Various methods for making the amino acid substitutions (mutations) provided herein are well known in the art, and are provided by, for example, Green and Sambrook, Molecular Cloning: A
• nuclease refers to an agent, for example, a protein, capable of cleaving a phosphodiester bond connecting two nucleotide residues in a nucleic acid molecule.
• nuclease refers to a protein having an inactive DNA cleavage domain, such that the nuclease is incapable of cleaving a phosphodiester bond.
• a nuclease is a protein, e.g., an enzyme that can bind a nucleic acid molecule and cleave a phosphodiester bond connecting nucleotide residues within the nucleic acid molecule.
• a nuclease may be an endonuclease, cleaving a phosphodiester bonds within a polynucleotide chain, or an exonuclease, cleaving a phosphodiester bond at the end of the polynucleotide chain.
• a nuclease is a site-specific nuclease, binding and/or cleaving a specific phosphodiester bond within a specific nucleotide sequence, which is also referred to herein as the "recognition sequence," the "nuclease target site,” or the “target site.”
• a nuclease is a RNA-guided (i.e., RNA-programmable) nuclease, which is associated with (e.g., binds to) an RNA (e.g., a guide RNA, "gRNA") having a sequence that complements a target site, thereby providing the sequence specificity of the nuclease.
• a nuclease recognizes a single stranded target site, while in other embodiments, a nuclease recognizes a double- stranded target site, for example, a double- stranded DNA target site.
• the target sites of many naturally occurring nucleases for example, many naturally occurring DNA restriction nucleases, are well known to those of skill in the art.
• a DNA nuclease such as EcoRI, Hindlll, or BamHI, recognize a palindromic, double- stranded DNA target site of 4 to 10 base pairs in length, and cut each of the two DNA strands at a specific position within the target site.
• Some endonucleases cut a double- stranded nucleic acid target site symmetrically, i.e., cutting both strands at the same position so that the ends comprise base-paired nucleotides, also referred to herein as blunt ends.
• Other endonucleases cut a double- stranded nucleic acid target sites asymmetrically, i.e., cutting each strand at a different position so that the ends comprise unpaired nucleotides.
• Unpaired nucleotides at the end of a double- stranded DNA molecule are also referred to as "overhangs,” e.g., as “5'-overhang” or as “3 '-overhang,” depending on whether the unpaired nucleotide(s) form(s) the 5' or the 5' end of the respective DNA strand.
• Double-stranded DNA molecule ends ending with unpaired nucleotide(s) are also referred to as sticky ends, as they can "stick to" other double- stranded DNA molecule ends comprising complementary unpaired nucleotide(s).
• a nuclease protein typically comprises a "binding domain” that mediates the interaction of the protein with the nucleic acid substrate, and also, in some cases, specifically binds to a target site, and a "cleavage domain” that catalyzes the cleavage of the phosphodiester bond within the nucleic acid backbone.
• a nuclease protein can bind and cleave a nucleic acid molecule in a monomeric form, while, in other embodiments, a nuclease protein has to dimerize or multimerize in order to cleave a target nucleic acid molecule.
• Binding domains and cleavage domains of naturally occurring nucleases, as well as modular binding domains and cleavage domains that can be fused to create nucleases binding specific target sites are well known to those of skill in the art.
• the binding domain of RNA-programmable nucleases e.g., Cas9
• a Cas9 protein having an inactive DNA cleavage domain can be used as a binding domain (e.g., that binds a gRNA to direct binding to a target site) to specifically bind a desired target site, and fused or conjugated to a cleavage domain, for example, the cleavage domain of Fokl, to create an engineered nuclease cleaving the target site.
• Cas9 fusion proteins provided herein comprise the cleavage domain of Fokl, and are therefore referred to as "fCas9" proteins.
• the cleavage domain of Fokl, e.g. , in a fCas9 protein corresponds to, or comprises in part or whole, the amino acid sequence (or variants thereof) set forth as SEQ ID NO:6, below.
• variants or homologues of the Fokl cleavage domain include any variant or homologue capable of dimerizing (e.g., as part of fCas9 fusion protein) with another Fokl cleavage domain at a target site in a target nucleic acid, thereby resulting in cleavage of the target nucleic acid.
• variants of the Fokl cleavage domain e.g., variants of SEQ ID NO:6 are provided which are at least about 70% identical, at least about 80% identical, at least about 90% identical, at least about 95% identical, at least about 98% identical, at least about 99% identical, at least about 99.5% identical, or at least about 99.9% to SEQ ID NO:6.
• variants of the Fokl cleavage domain are provided having an amino acid sequence which is shorter, or longer than SEQ ID NO:6, by about 5 amino acids, by about 10 amino acids, by about 15 amino acids,, by about 20 amino acids, by about 25 amino acids, by about 30 amino acids, by about 40 amino acids, by about 50 amino acids, by about 75 amino acids, by about 100 amino acids or more.
• nucleic acid and “nucleic acid molecule,” as used herein, refer to a compound comprising a nucleobase and an acidic moiety, e.g., a nucleoside, a nucleotide, or a polymer of nucleotides.
• polymeric nucleic acids e.g., nucleic acid molecules comprising three or more nucleotides are linear molecules, in which adjacent nucleotides are linked to each other via a phosphodiester linkage.
• nucleic acid refers to individual nucleic acid residues (e.g. nucleotides and/or nucleosides).
• nucleic acid refers to an oligonucleotide chain comprising three or more individual nucleotide residues.
• oligonucleotide and
• nucleic acid can be used interchangeably to refer to a polymer of nucleotides (e.g., a string of at least three nucleotides).
• nucleic acid encompasses RNA as well as single and/or double- stranded DNA.
• Nucleic acids may be naturally occurring, for example, in the context of a genome, a transcript, an mRNA, tRNA, rRNA, siRNA, snRNA, gRNA, a plasmid, cosmid, chromosome, chromatid, or other naturally occurring nucleic acid molecule.
• a nucleic acid molecule may be a non-naturally occurring molecule, e.g.
• nucleic acid a recombinant DNA or RNA, an artificial chromosome, an engineered genome, or fragment thereof, or a synthetic DNA, RNA, DNA/RNA hybrid, or including non-naturally occurring nucleotides or nucleosides.
• nucleic acid DNA
• RNA and/or similar terms include nucleic acid analogs, i.e. analogs having other than a phosphodiester backbone. Nucleic acids can be purified from natural sources, produced using recombinant expression systems and optionally purified, chemically synthesized, etc.
• nucleic acids can comprise nucleoside analogs such as analogs having chemically modified bases or sugars, and backbone modifications.
• a nucleic acid sequence is presented in the 5' to 3' direction unless otherwise indicated.
• a nucleic acid is or comprises natural nucleosides (e.g.
• nucleoside analogs e.g., 2-aminoadenosine, 2-thiothymidine, inosine, pyrrolo-pyrimidine, 3-methyl adenosine, 5-methylcytidine, 2-aminoadenosine, C5-bromouridine, C5-fluorouridine, C5-iodouridine, C5-propynyl-uridine, C5-propynyl-cytidine, C5-methylcytidine, 2-aminoadenosine, 7- deazaadenosine, 7-deazaguanosine, 8-oxoadenosine, 8-oxoguanosine, 0(6)-methylguanine, and 2-thiocyt
• methylated bases e.g., methylated bases
• intercalated bases e.g., modified sugars (e.g., 2'-fluororibose, ribose, 2'-deoxyribose, arabinose, and hexose); and/or modified phosphate groups (e.g., phosphorothioates and 5'-N- phosphoramidite linkages).
• modified sugars e.g., 2'-fluororibose, ribose, 2'-deoxyribose, arabinose, and hexose
• modified phosphate groups e.g., phosphorothioates and 5'-N- phosphoramidite linkages.
• composition refers to a pharmaceutical composition
• a pharmaceutical composition that can be administrated to a subject in the context of treatment and/or prevention of a disease or disorder.
• a pharmaceutical composition comprises an active ingredient, e.g., a nuclease or recombinase fused to a Cas9 protein, or fragment thereof (or a nucleic acid encoding a such a fusion), and optionally a
• a pharmaceutical composition comprises inventive Cas9 variant/fusion (e.g. , fCas9) protein(s) and gRNA(s) suitable for targeting the Cas9 variant/fusion protein(s) to a target nucleic acid.
• inventive Cas9 variant/fusion e.g. , fCas9 protein(s) and gRNA(s) suitable for targeting the Cas9 variant/fusion protein(s) to a target nucleic acid.
• the target nucleic acid is a gene.
• the target nucleic acid is an allele associated with a disease, whereby the allele is cleaved by the action of the Cas9
• the allele is an allele of the CLTA gene, the EMX gene, the HBB gene, the VEGF gene, or the CCR5 gene. See e.g. , the Examples;
• proliferative disease refers to any disease in which cell or tissue homeostasis is disturbed in that a cell or cell population exhibits an abnormally elevated proliferation rate.
• Proliferative diseases include hyperproliferative diseases, such as pre-neoplastic hyperplastic conditions and neoplastic diseases.
• Neoplastic diseases are characterized by an abnormal proliferation of cells and include both benign and malignant neoplasias. Malignant neoplasia is also referred to as cancer.
• compositions and methods provided herein are useful for treating a proliferative disease.
• pharmaceutical compositions comprising Cas9 (e.g., fCas9) protein(s) and gRNA(s) suitable for targeting the Cas9 protein(s) to an VEGF allele, whereby the allele is inactivated by the action of the Cas9 protein(s). See, e.g. , the Examples.
• protein refers to a polymer of amino acid residues linked together by peptide (amide) bonds.
• the terms refer to a protein, peptide, or polypeptide of any size, structure, or function. Typically, a protein, peptide, or polypeptide will be at least three amino acids long.
• a protein, peptide, or polypeptide may refer to an individual protein or a collection of proteins.
• One or more of the amino acids in a protein, peptide, or polypeptide may be modified, for example, by the addition of a chemical entity such as a carbohydrate group, a hydroxyl group, a phosphate group, a farnesyl group, an isofarnesyl group, a fatty acid group, a linker for conjugation, functionalization, or other modification, etc.
• a protein, peptide, or polypeptide may also be a single molecule or may be a multi-molecular complex.
• a protein, peptide, or polypeptide may be just a fragment of a naturally occurring protein or peptide.
• a protein, peptide, or polypeptide may be naturally occurring, recombinant, or synthetic, or any combination thereof.
• fusion protein refers to a hybrid polypeptide which comprises protein domains from at least two different proteins.
• One protein may be located at the amino-terminal (N-terminal) portion of the fusion protein or at the carboxy- terminal (C-terminal) protein thus forming an "amino-terminal fusion protein” or a "carboxy- terminal fusion protein,” respectively.
• Any of the proteins provided herein may be produced by any method known in the art.
• the proteins provided herein may be produced via recombinant protein expression and purification, which is especially suited for fusion proteins comprising a peptide linker.
• RNA -programmable nuclease and "RNA-guided nuclease” are used interchangeably herein and refer to a nuclease that forms a complex with ⁇ e.g., binds or associates with) one or more RNA that is not a target for cleavage.
• an RNA-programmable nuclease when in a complex with an RNA, may be referred to as a nuclease:RNA complex.
• the bound RNA(s) is referred to as a guide RNA
• gRNAs can exist as a complex of two or more RNAs, or as a single RNA molecule. gRNAs that exist as a single RNA molecule may be referred to as single-guide RNAs (sgRNAs), though "gRNA” is used interchangeabley to refer to guide RNAs that exist as either single molecules or as a complex of two or more molecules.
• sgRNAs single-guide RNAs
• gRNAs that exist as single RNA species comprise two domains: (1) a domain that shares homology to a target nucleic acid ⁇ e.g., and directs binding of a Cas9 complex to the target); and (2) a domain that binds a Cas9 protein.
• domain (2) corresponds to a sequence known as a tracrRNA, and comprises a stem-loop structure.
• domain (2) is homologous to a tracrRNA as depicted in Figure IE of Jinek et al., Science 337:816-821(2012), the entire contents of which is incorporated herein by reference.
• Other examples of gRNAs e.g., those including domain 2 can be found in U.S. Provisional Patent Application, U.S.S.N. 61/874,682, filed September 6, 2013, entitled "Switchable Cas9 Nucleases And Uses Thereof;" U.S. Provisional Patent Application, U.S.S.N.
• gRNAs and gRNA structure are provided herein. See e.g., the Examples.
• a gRNA comprises two or more of domains (1) and (2), and may be referred to as an "extended gRNA.”
• an extended gRNA will e.g., bind two or more Cas9 proteins and bind a target nucleic acid at two or more distinct regions, as described herein.
• the gRNA comprises a nucleotide sequence that complements a target site, which mediates binding of the nuclease/RNA complex to said target site, providing the sequence specificity of the nuclease:RNA complex.
• the RNA-programmable nuclease is the (CRISPR-associated system) Cas9 endonuclease, for example Cas9 (Csnl) from
• Streptococcus pyogenes see, e.g., "Complete genome sequence of an Ml strain of Streptococcus pyogenes (see, e.g., "Complete genome sequence of an Ml strain of Streptococcus pyogenes (see, e.g., "Complete genome sequence of an Ml strain of Streptococcus pyogenes (see, e.g., "Complete genome sequence of an Ml strain of
• RNA-programmable nucleases e.g., Cas9
• RNA-programmable nucleases such as Cas9
• site-specific cleavage e.g., to modify a genome
• Methods of using RNA-programmable nucleases, such as Cas9, for site-specific cleavage are known in the art (see e.g., Cong, L. et al. Multiplex genome engineering using CRISPR/Cas systems. Science 339, 819-823 (2013); Mali, P. et al. RNA-guided human genome engineering via Cas9. Science 339, 823-826 (2013); Hwang, W.Y. et al. Efficient genome editing in zebrafish using a CRISPR-Cas system.
• recombinase refers to a site-specific enzyme that mediates the recombination of DNA between recombinase recognition sequences, which results in the excision, integration, inversion, or exchange (e.g., translocation) of DNA fragments between the recombinase recognition sequences.
• Recombinases can be classified into two distinct families: serine recombinases (e.g., resolvases and invertases) and tyrosine recombinases (e.g., integrases).
• serine recombinases include, without limitation, Hin, Gin, Tn3, ⁇ -six, CinH, ParA, ⁇ , Bxbl, 4>C31, TP901, TGI, ⁇ , R4, cpRVl, cpFCl, MRU, Al 18, U153, and gp29.
• tyrosine recombinases include, without limitation, Cre, FLP, R, Lambda, HK101, HK022, and pSAM2.
• the serine and tyrosine recombinase names stem from the conserved nucleophilic amino acid residue that the recombinase uses to attack the DNA and which becomes covalently linked to the DNA during strand exchange.
• Recombinases have numerous applications, including the creation of gene knockouts/knock-ins and gene therapy applications. See, e.g., Brown et al., "Serine recombinases as tools for genome engineering.” Methods. 2011;53(4):372-9; Hirano et al., "Site-specific recombinases as tools for heterologous gene integration.” Appl. Microbiol. Biotechnol. 2011; 92(2):227-39; Chavez and Calos, "Therapeutic applications of the OC31 integrase system.” Curr. Gene Ther.
• recombinases provided herein are not meant to be exclusive examples of recombinases that can be used in embodiments of the invention.
• the methods and compositions of the invention can be expanded by mining databases for new orthogonal recombinases or designing synthetic recombinases with defined DNA specificities (See, e.g., Groth et al., "Phage integrases: biology and applications.” J. Mol. Biol. 2004; 335, 667-678; Gordley et al., "Synthesis of programmable integrases.” Proc. Natl. Acad. Sci. U S A.
• the catalytic domains of a recombinase are fused to a nuclease-inactivated RNA-programmable nuclease ⁇ e.g., dCas9, or a fragment thereof), such that the recombinase domain does not comprise a nucleic acid binding domain or is unable to bind to a target nucleic acid ⁇ e.g., the recombinase domain is engineered such that it does not have specific DNA binding activity).
• Recombinases lacking DNA binding activity and methods for engineering are known, and include those described by Klippel et al., "Isolation and characterisation of unusual gin mutants.” EMBO J.
• serine recombinases of the resolvase-invertase group e.g., Tn3 and ⁇ resolvases and the Hin and Gin invertases
• Tn3 and ⁇ resolvases and the Hin and Gin invertases have modular structures with autonomous catalytic and DNA -binding domains (See, e.g., Grindley et al., "Mechanism of site-specific recombination.” Ann Rev Biochem. 2006; 75: 567-605, the entire contents of which are incorporated by reference).
• RNA-programmable nucleases e.g., dCas9, or a fragment thereof
• RNA-programmable nucleases e.g., dCas9, or a fragment thereof
• accessory factors e.g., DNA binding activities
• transposase and their catalytic domains can be co-opted to engineer programmable site- specific recombinases as described herein (See, e.g., Smith et al., "Diversity in the serine recombinases.” Mol Microbiol. 2002;44: 299-307, the entire contents of which are incorporated by reference).
• tyrosine recombinases e.g., Cre, ⁇ integrase
• Cre tyrosine recombinases
• ⁇ integrase the core catalytic domains of tyrosine recombinases
• Cre ⁇ integrase
• programmable site-specific recombinases See, e.g., Guo et al., "Structure of Cre recombinase complexed with DNA in a site-specific recombination synapse.” Nature.
• nucleic acid modification e.g., a genomic modification
• recombinase protein e.g., an inventive recombinase fusion protein provided herein. Recombination can result in, inter alia, the insertion, inversion, excision or translocation of nucleic acids, e.g., in or between one or more nucleic acid molecules.
• the term "subject,” as used herein, refers to an individual organism, for example, an individual mammal.
• the subject is a human.
• the subject is a non-human mammal.
• the subject is a non-human primate.
• the subject is a rodent.
• the subject is a sheep, a goat, a cattle, a cat, or a dog.
• the subject is a vertebrate, an amphibian, a reptile, a fish, an insect, a fly, or a nematode.
• the subject is a research animal.
• the subject is genetically engineered, e.g., a genetically engineered non-human subject.
• the subject may be of either sex and at any stage of development.
• target nucleic acid refers to a nucleic acid molecule or a genome, respectively, that comprises at least one target site of a given nuclease.
• a target nucleic acid and a target genome refers to one or more nucleic acid molecule(s), or a genome, respectively, that comprises at least one target site.
• the target nucleic acid(s) comprises at least two, at least three, or at least four target sites. In some embodiments, the target nucleic acid(s) comprise four target sites.
• target site refers to a sequence within a nucleic acid molecule that is either (1) bound and cleaved by a nuclease (e.g., Cas9 fusion proteins provided herein), or (2) bound and recombined (e.g., at or nearby the target site) by a recombinase (e.g., a dCas9- recombinase fusion protein provided herein).
• a target site may be single- stranded or double- stranded.
• RNA-guided nucleases e.g., a protein dimer comprising a Cas9 gRNA binding domain and an active Cas9 DNA cleavage domain or other nuclease domain such as Fokl
• a target site typically comprises a nucleotide sequence that is complementary to the gRNA(s) of the RNA-programmable nuclease, and a protospacer adjacent motif (PAM) at the 3' end adjacent to the gRNA-complementary sequence(s).
• PAM protospacer adjacent motif
• a target site can encompass the particular sequences to which fCas9 monomers bind, and/or the intervening sequence between the bound monomers that are cleaved by the dimerized Fokl domains (See e.g. , the Examples; and Figures 1A, 6D).
• RNA-guided e.g., RNA-programmable, nuclease-inactivated
• a recombinase e.g.
• a catalytic domain of a recombinase typically comprises a nucleotide sequence that is complementary to the gRNA of the RNA-programmable nuclease domain, and a protospacer adjacent motif (PAM) at the 3' end adjacent to the gRNA-complementary sequence.
• PAM protospacer adjacent motif
• four recombinase monomers are coordinated to recombine a target nucleic acid(s), each monomer being fused to a (nuclease-inactivated) Cas9 protein guided by a gRNA.
• each Cas9 domain is guided by a distinct gRNA to bind a target nucleic acid(s), thus the target nucleic acid comprises four target sites, each site targeted by a separate dCas9-recombinase fusion (thereby coordinating four recombinase monomers which recombine the target nucleic acid(s)).
• the target site may be, in some embodiments, 17-20 base pairs plus a 3 base pair PAM (e.g. , NNN, wherein N independently represents any nucleotide).
• the first nucleotide of a PAM can be any nucleotide, while the two downstream nucleotides are specified depending on the specific RNA-guided nuclease.
• exemplary target sites e.g. , comprising a PAM
• RNA-guided nucleases such as Cas9
• Cas9 nucleases from different species e.g. , S. thermophilus instead of S. pyogenes
• S. thermophilus instead of S. pyogenes
• the target site of an RNA-guided nuclease such as, e.g., Cas9, may comprise the structure [Nz]-[PAM], where each N is, independently, any nucleotide, and z is an integer between 1 and 50, inclusive.
• z is at least 2, at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 11, at least 12, at least 13, at least 14, at least 15, at least 16, at least 17, at least 18, at least 19, at least 20, at least 25, at least 30, at least 35, at least 40, at least 45, or at least 50.
• z is 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,49, or 50.
• z is 20.
• target site may also refer to a sequence within a nucleic acid molecule that is bound but not cleaved by a nuclease.
• certain embodiments described herein provide proteins comprising an inactive (or inactivated) Cas9 DNA cleavage domain. Such proteins (e.g. , when also including a Cas9 RNA binding domain) are able to bind the target site specified by the gRNA; however, because the DNA cleavage site is inactivated, the target site is not cleaved by the particular protein.
• proteins as described herein are typically conjugated, fused, or bound to another protein (e.g., a nuclease) or molecule that mediates cleavage of the nucleic acid molecule.
• a nuclease e.g., a nuclease
• such proteins are conjugated, fused, or bound to a recombinase (or a catalytic domain of a recombinase), which mediates recombination of the target nucleic acid.
• the sequence actually cleaved or recombined will depend on the protein (e.g.
• nuclease or recombinase or molecule that mediates cleavage or recombination of the nucleic acid molecule, and in some cases, for example, will relate to the proximity or distance from which the inactivated Cas9 protein(s) is/are bound.
• a target site typically comprises a left-half site (bound by one protein), a right-half site (bound by the second protein), and a spacer sequence between the half sites in which the cut or recombination is made.
• either the left-half site or the right half-site is cut or recombined.
• the spacer sequence is cut or recombined.
• This structure ([left-half site] -[spacer sequence] -[right-half site]) is referred to herein as an LSR structure.
• the left-half site and/or the right-half site correspond to an RNA-guided target site (e.g., a Cas9 target site).
• either or both half- sites are shorter or longer than e.g. , a typical region targeted by Cas9, for example shorter or longer than 20 nucleotides.
• the left and right half sites comprise different nucleic acid sequences.
• the target site is a sequence comprising three (3) RNA-guided nuclease target site sequences, for example, three sequences corresponding to Cas9 target site sequences (See, e.g., Figure 2C), in which the first and second, and second and third Cas9 target site sequences are separated by a spacer sequence.
• the spacer sequence is at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 11, at least 12, at least 13, at least 14, at least 15, at least 16, at least 17, at least 18, at least 19, at least 20, at least 25, at least 30, at least 35, at least 40, at least 45, at least 50, at least 60, at least 70, at least 80, at least 90, at least 100, at least 125, at least 150, at least 175, at least 200, or at least 250 bp long. In some embodiments, the spacer sequence is between approximately 15 bp and approximately 25 bp long. In some embodiments, the spacer sequence is approximately 15 bp long. In some embodiments, the spacer sequence is approximately 25 bp long.
• TALE Transcriptional Activator-Like Effector
• RVD Repeat Variable Diresidue
• the RVD motif determines binding specificity to a nucleic acid sequence and can be engineered according to methods known to those of skill in the art to specifically bind a desired DNA sequence (see, e.g., Miller, Jeffrey; et.al. (February 2011). "A TALE nuclease architecture for efficient genome editing". Nature
• TALEN Transcriptional Activator-Like Element Nuclease
• TALEN Transcriptional Activator-Like Element Nuclease
• a number of modular assembly schemes for generating engineered TALE constructs have been reported (see e.g., Zhang, Feng; et.al. (February 2011). "Efficient construction of sequence- specific TAL effectors for modulating mammalian transcription". Nature Biotechnology 29 (2): 149- 53; Geipier, R.; Scholze, H.; Hahn, S.; Streubel, J.; Bonas, U.; Behrens, S. E.; Boch, J.
• treatment refers to a clinical intervention aimed to reverse, alleviate, delay the onset of, or inhibit the progress of a disease or disorder, or one or more symptoms thereof, as described herein.
• treatment refers to a clinical intervention aimed to reverse, alleviate, delay the onset of, or inhibit the progress of a disease or disorder, or one or more symptoms thereof, as described herein.
• treatment may be administered after one or more symptoms have developed and/or after a disease has been diagnosed.
• treatment may be administered in the absence of symptoms, e.g., to prevent or delay onset of a symptom or inhibit onset or progression of a disease.
• treatment may be administered to a susceptible individual prior to the onset of symptoms (e.g., in light of a history of symptoms and/or in light of genetic or other susceptibility factors). Treatment may also be continued after symptoms have resolved, for example, to prevent or delay their recurrence.
• vector refers to a polynucleotide comprising one or more recombinant polynucleotides of the present invention, e.g., those encoding a Cas9 protein (or fusion thereof) and/or gRNA provided herein.
• Vectors include, but are not limited to, plasmids, viral vectors, cosmids, artificial chromosomes, and phagemids.
• the vector is able to replicate in a host cell and is further characterized by one or more endonuclease restriction sites at which the vector may be cut and into which a desired nucleic acid sequence may be inserted.
• Vectors may contain one or more marker sequences suitable for use in the identification and/or selection of cells which have or have not been transformed or genomically modified with the vector.
• Markers include, for example, genes encoding proteins which increase or decrease either resistance or sensitivity to antibiotics (e.g., kanamycin, ampicillin) or other compounds, genes which encode enzymes whose activities are detectable by standard assays known in the art (e.g., ⁇ -galactosidase, alkaline
• any vector suitable for the transformation of a host cell e.g., E. coli, mammalian cells such as CHO cell, insect cells, etc.
• a host cell e.g., E. coli, mammalian cells such as CHO cell, insect cells, etc.
• vectors belonging to the pUC series, pGEM series, pET series, pBAD series, pTET series, or pGEX series for example, vectors belonging to the pUC series, pGEM series, pET series, pBAD series, pTET series, or pGEX series.
• the vector is suitable for transforming a host cell for recombinant protein production.
• Zinc finger refers to a small nucleic acid-binding protein structural motif characterized by a fold and the coordination of one or more zinc ions that stabilize the fold.
• Zinc fingers encompass a wide variety of differing protein structures (see, e.g., Klug A, Rhodes D (1987). "Zinc fingers: a novel protein fold for nucleic acid recognition”. Cold Spring Harb. Symp. Quant. Biol. 52: 473-82, the entire contents of which are incorporated herein by reference).
• Zinc fingers can be designed to bind a specific sequence of nucleotides, and zinc finger arrays comprising fusions of a series of zinc fingers, can be designed to bind virtually any desired target sequence.
• Such zinc finger arrays can form a binding domain of a protein, for example, of a nuclease, e.g., if conjugated to a nucleic acid cleavage domain.
• a nuclease e.g., if conjugated to a nucleic acid cleavage domain.
• Different types of zinc finger motifs are known to those of skill in the art, including, but not limited to, Cys 2 His 2 , Gag knuckle, Treble clef, Zinc ribbon, Zn 2 /Cys 6 , and TAZ2 domain-like motifs (see, e.g., Krishna SS, Majumdar I, Grishin NV (January 2003). "Structural classification of zinc fingers: survey and summary". Nucleic Acids Res. 31 (2): 532-50).
• a single zinc finger motif binds 3 or 4 nucleotides of a nucleic acid molecule.
• a zinc finger domain comprising 2 zinc finger motifs may bind 6-8 nucleotides
• a zinc finger domain comprising 3 zinc finger motifs may bind 9- 12 nucleotides
• a zinc finger domain comprising 4 zinc finger motifs may bind 12-16 nucleotides, and so forth.
• Any suitable protein engineering technique can be employed to alter the DNA -binding specificity of zinc fingers and/or design novel zinc finger fusions to bind virtually any desired target sequence from 3 - 30 nucleotides in length (see, e.g., Pabo CO, Peisach E, Grant RA (2001).
• a zinc finger nuclease typically comprises a zinc finger domain that binds a specific target site within a nucleic acid molecule, and a nucleic acid cleavage domain that cuts the nucleic acid molecule within or in proximity to the target site bound by the binding domain.
• Typical engineered zinc finger nucleases comprise a binding domain having between 3 and 6 individual zinc finger motifs and binding target sites ranging from 9 base pairs to 18 base pairs in length. Longer target sites are particularly attractive in situations where it is desired to bind and cleave a target site that is unique in a given genome.
• Zinc finger nuclease refers to a nuclease comprising a nucleic acid cleavage domain conjugated to a binding domain that comprises a zinc finger array.
• the cleavage domain is the cleavage domain of the type II restriction endonuclease Fokl.
• Zinc finger nucleases can be designed to target virtually any desired sequence in a given nucleic acid molecule for cleavage, and the possibility to design zinc finger binding domains to bind unique sites in the context of complex genomes allows for targeted cleavage of a single genomic site in living cells, for example, to achieve a targeted genomic alteration of therapeutic value.
• Zinc finger nucleases can be generated to target a site of interest by methods well known to those of skill in the art. For example, zinc finger binding domains with a desired specificity can be designed by combining individual zinc finger motifs of known specificity. The structure of the zinc finger protein Zif268 bound to DNA has informed much of the work in this field and the concept of obtaining zinc fingers for each of the 64 possible base pair triplets and then mixing and matching these modular zinc fingers to design proteins with any desired sequence specificity has been described (Pavletich NP, Pabo CO (May 1991).
• Zinc finger-DNA recognition crystal structure of a Zif268-DNA complex at 2.1 A. Science 252 (5007): 809-17, the entire contents of which are incorporated herein).
• separate zinc fingers that each recognizes a 3 base pair DNA sequence are combined to generate 3-, 4-, 5-, or 6-finger arrays that recognize target sites ranging from 9 base pairs to 18 base pairs in length. In some embodiments, longer arrays are contemplated.
• 2-finger modules recognizing 6-8 nucleotides are combined to generate 4-, 6-, or 8- zinc finger arrays.
• bacterial or phage display is employed to develop a zinc finger domain that recognizes a desired nucleic acid sequence, for example, a desired nuclease target site of 3-30 bp in length.
• Zinc finger nucleases in some embodiments, comprise a zinc finger binding domain and a cleavage domain fused or otherwise conjugated to each other via a linker, for example, a polypeptide linker. The length of the linker determines the distance of the cut from the nucleic acid sequence bound by the zinc finger domain.
• the cleavage domain of a zinc finger nuclease has to dimerize in order to cut a bound nucleic acid.
• the dimer is a heterodimer of two monomers, each of which comprise a different zinc finger binding domain.
• the dimer may comprise one monomer comprising zinc finger domain A conjugated to a Fokl cleavage domain, and one monomer comprising zinc finger domain B conjugated to a Fokl cleavage domain.
• zinc finger domain A binds a nucleic acid sequence on one side of the target site
• zinc finger domain B binds a nucleic acid sequence on the other side of the target site
• the dimerize Fokl domain cuts the nucleic acid in between the zinc finger domain binding sites.
• Site-specific nucleases and site-specific recombinases are powerful tools for targeted genome modification in vitro and in vivo. It has been reported that nuclease cleavage in living cells triggers a DNA repair mechanism that frequently results in a modification of the cleaved and repaired genomic sequence, for example, via homologous recombination. Accordingly, the targeted cleavage of a specific unique sequence within a genome opens up new avenues for gene targeting and gene modification in living cells, including cells that are hard to manipulate with conventional gene targeting methods, such as many human somatic or embryonic stem cells. Another approach utilizes site-specific recombinases, which possess all the functionality required to bring about efficient, precise integration, deletion, inversion, or translocation of specified DNA segments.
• Nuclease-mediated modification of disease-related sequences can be used in the clinical context, and two site specific nucleases are currently in clinical trials (Perez, E.E. et al., "Establishment of HIV-1 resistance in CD4+ T cells by genome editing using zinc-finger nucleases.” Nature biotechnology. 26, 808-816 (2008); ClinicalTrials.gov identifiers: NCT00842634, NCT01044654, NCT01252641, NCT01082926).
• any genetic disease can be treated using site-specific nucleases and/or recombinases and include, for example, diseases associated with triplet expansion (e.g., Huntington's disease, myotonic dystrophy, spinocerebellar ataxias, etc.), cystic fibrosis (by targeting the CFTR gene), hematological disease (e.g., hemoglobinopathies), cancer, autoimmune diseases, and viral infections.
• diseases associated with triplet expansion e.g., Huntington's disease, myotonic dystrophy, spinocerebellar ataxias, etc.
• cystic fibrosis by targeting the CFTR gene
• hematological disease e.g., hemoglobinopathies
• adrenoleukodystrophy aicardi syndrome, alpha- 1 antitrypsin deficiency, alpha-thalassemia, androgen insensitivity syndrome, apert syndrome, arrhythmogenic right ventricular, dysplasia, ataxia telangictasia, barth syndrome, beta-thalassemia, blue rubber bleb nevus syndrome, canavan disease, chronic granulomatous diseases (CGD), cri du chat syndrome, dercum's disease, ectodermal dysplasia, fanconi anemia, fibrodysplasia ossificans
• One aspect of site-specific genomic modification is the possibility of off-target nuclease or recombinase effects, e.g. , the cleavage or recombination of genomic sequences that differ from the intended target sequence by one or more nucleotides.
• Undesired side effects of off-target cleavage/recombination range from insertion into unwanted loci during a gene targeting event to severe complications in a clinical scenario.
• Off-target cleavage or recombination of sequences encoding essential gene functions or tumor suppressor genes by an endonuclease or recombinase administered to a subject may result in disease or even death of the subject. Accordingly, it is desirable to employ new strategies in designing nucleases and recombinases having the greatest chance of minimizing off-target effects.
• nucleases and recombinases represent, in some aspects, an improvement over previous methods and compositions providing nucleases (and methods of their use) and recombinases (and methods of their use) engineered to have improved specificity for their intended targets.
• nucleases and recombinases known in the art both naturally occurring and those engineered, typically have a target (e.g. , DNA) binding domain that recognizes a particular sequence.
• known nucleases and recombinases may comprise a DNA binding domain and a catalytic domain in a single protein capable of inducing cleavage or recombination, and as such the chance for off-target effects are increased as cleavage or recombination likely occurs upon off-target binding of the nuclease or recombinase, respectively.
• Aspects of the present invention relate to the recognition that increasing the number of sequences (e.g.
• nuclease having a nuclease bind at more than one site at a desired target), and/or splitting the activities (e.g., target binding and target cleaving) of a nuclease between two or more proteins, will increase the specificity of a nuclease and thereby decrease the likelihood of off-target effects.
• Other aspects of the present invention relate to the recognition that fusions between the catalytic domain of recombinases (or recombinases having inactive DNA binding domains) and nuclease - inactivated RNA-programmable nucleases allow for the targeted recombination of DNA at any location.
• any site-specific nuclease for example, variants of the Cas9 endonuclease, Zinc Finger Nucleases (ZFNs) and Transcription Activator- Like Effector Nucleases (TALENs).
• ZFNs Zinc Finger Nucleases
• TALENs Transcription Activator- Like Effector Nucleases
• the strategies, methods, compositions, and systems provided herein are utilized to improve the specificity of the RNA-guided (e.g., RNA- programmable) endonuclease Cas9.
• RNA-guided e.g., RNA- programmable
• Cas9 endonuclease uses RNA:DNA hybridization to determine target DNA cleavage sites, enabling a single monomeric protein to cleave, in principle, any sequence specified by the guide RNA (gRNA).
• gRNA guide RNA
• Cas9:guide RNA complexes have been successfully used to modify both cells (Cong, L. et al. Multiplex genome engineering using CRISPR/Cas systems. Science.
• nickases enable double- stranded breaks to be specified by two distinct gRNA sequences
• nickases enable double- stranded breaks to be specified by two distinct gRNA sequences
• aspects of the present disclosure aim at reducing the chances for Cas9 off-target effects using novel engineered Cas9 variants.
• a Cas9 variant (e.g., fCas9) which has improved specificity as compared to the Cas9 nickases or wild type Cas9, exhibiting, e.g., >10-fold, >50-fold, >100-fold, >140-fold, > 200-fold, or more, higher specificity than wild type Cas9 (see e.g., the Examples).
• RNA-guided e.g., RNA-programmable
• Cas9-recombinase fusion proteins use RNA:DNA hybridization to determine target DNA recombination sites, enabling the fusion proteins to recombine, in principle, any region specified by the gRNA(s).
• nucleic acid:nuclease or nucleic acid:recombinase system While of particular relevance to DNA and DNA-cleaving nucleases and/or recombinases, the inventive concepts, methods, strategies and systems provided herein are not limited in this respect, but can be applied to any nucleic acid:nuclease or nucleic acid:recombinase system.
• Some aspects of this disclosure provide site-specific nucleases with enhanced specificity that are designed using the methods and strategies described herein. Some embodiments of this disclosure provide nucleic acids encoding such nucleases. Some embodiments of this disclosure provide expression constructs comprising such encoding nucleic acids (See, e.g., Figure 20). For example, in some embodiments an isolated nuclease is provided that has been engineered to cleave a desired target site within a genome. In some embodiments, the isolated nuclease is a variant of an RNA-programmable nuclease, such as a Cas9 nuclease.
• fusion proteins comprising two domains: (i) an RNA-programmable nuclease (e.g. , Cas9 protein, or fragment thereof) domain fused or linked to (ii) a nuclease domain.
• the Cas9 protein e.g., the Cas9 domain of the fusion protein
• comprises a nuclease-inactivated Cas9 e.g., a Cas9 lacking DNA cleavage activity; "dCas9”
• gRNA RNA binding activity
• the nuclease fused to the nuclease-inactivated Cas9 domain is any nuclease requiring dimerization (e.g., the coming together of two monomers of the nuclease) in order to cleave a target nucleic acid (e.g., DNA).
• the nuclease fused to the nuclease-inactivated Cas9 is a monomer of the Fokl DNA cleavage domain, e.g., thereby producing the Cas9 variant referred to as fCas9.
• the Fokl DNA cleavage domain is known, and in some aspects corresponds to amino acids 388-583 of Fokl (NCBI accession number J04623).
• the Fokl DNA cleavage domain corresponds to amino acids 300-583, 320-583, 340-583, or 360-583 of Fokl. See also Wah et al., "Structure of Fokl has implications for DNA cleavage” Proc. Natl. Acad. Sci. USA. 1998; 1;95(18): 10564-9; Li et al., "TAL nucleases (TALNs): hybrid proteins composed of TAL effectors and Fokl DNA-cleavage domain” Nucleic Acids Res. 2011; 39(l):359-72; Kim et al., "Hybrid restriction enzymes: zinc finger fusions to Fok I cleavage domain” Proc. Natl Acad. Sci. USA. 1996; 93: 1156- 1160; the entire contents of each are herein incorporated by reference).
• TAL nucleases TALNs
• Hybrid restriction enzymes zinc finger fusions to Fok I cleavage domain
• the Fokl DNA cleavage domain corresponds to, or comprises in part or whole, the amino acid sequence set forth as SEQ ID NO:6.
• the Fokl DNA cleavage domain is a variant of Fokl (e.g., a variant of SEQ ID NO:6), as described herein.
• a dimer of the fusion protein is provided, e.g., dimers of fCas9.
• the fusion protein forms a dimer with itself to mediate cleavage of the target nucleic acid.
• the fusion proteins, or dimers thereof are associated with one or more gRNAs.
• the dimer contains two fusion proteins, each having a Cas9 domain having gRNA binding activity, a target nucleic acid is targeted using two distinct gRNA sequences that complement two distinct regions of the nucleic acid target. See, e.g., Figures 1A, 6D.
• cleavage of the target nucleic acid does not occur until both fusion proteins bind the target nucleic acid (e.g., as specified by the gRNA:target nucleic acid base pairing), and the nuclease domains dimerize (e.g., the Fokl DNA cleavage domains; as a result of their proximity based on the binding of the Cas9:gRNA domains of the fusion proteins) and cleave the target nucleic acid, e.g., in the region between the bound Cas9 fusion proteins (the "spacer sequence").
• the target nucleic acid e.g., as specified by the gRNA:target nucleic acid base pairing
• the nuclease domains dimerize e.g., the Fokl DNA cleavage domains; as a result of their proximity based on the binding of the Cas9:gRNA domains of the fusion proteins
• nickase variants can induce cleaving, or nicking upon binding of a single nickase to a nucleic acid, which can occur at on- and off-target sites, and nicking is known to induce mutagenesis.
• An exemplary nucleotide encoding a Cas9 nickase (SEQ ID NO:7) and an exemplary amino acid sequence of Cas9 nickase (SEQ ID NO: 8) are provided below.
• the variants provided herein require the binding of two Cas9 variants in proximity to one another to induce target nucleic acid cleavage, the chances of inducing off-target cleavage is reduced. See, e.g. , the Examples.
• a Cas9 variant fused to a nuclease domain has an on-target:off-target modification ratio that is at least 2- fold, at least 5-fold, at least 10-fold, at least 20-fold, at least 30-fold, at least 40-fold, at least 50-fold, at least 60-fold, at least 70-fold, at least 80-fold, at least 90-fold, at least 100-fold, at least 110-fold, at least 120-fold, at least 130-fold, at least 140-fold, at least 150-fold, at least 175-fold, at least 200-fold, at least 250-fold, or more higher than the on-target:off-target modification ratio of a wild type Cas9 or other Cas9 variant (e.g.
• a Cas9 variant fused to a nuclease domain has an on-target: off- target modification ratio that is between about 60- to 180-fold, between about 80- to 160-fold, between about 100- to 150-fold, or between about 120- to 140-fold higher than the on- target: off-target modification ratio of a wild type Cas9 or other Cas9 variant.
• Methods for determining on-target: off-target modification ratios are known, and include those described in the Examples.
• the on-target: off-target modification ratios are determined by measuring the number or amount of modifications of known Cas9 off-target sites in certain genes.
• the Cas9 off-target sites of the CLTA, EMX, and VEGF genes are known, and modifications at these sites can be measured and compared between test proteins and controls.
• the target site and its corresponding known off-target sites are amplified from genomic DNA isolated from cells (e.g. , HEK293) treated with a particular Cas9 protein or variant. The modifications are then analyzed by high-throughput sequencing.
• Sequences containing insertions or deletions of two or more base pairs in potential genomic off-target sites and present in significantly greater numbers (P value ⁇ 0.005, Fisher's exact test) in the target gRNA-treated samples versus the control gRNA-treated samples are considered Cas9 nuclease-induced genome modifications.
• the gRNAs which bind the Cas9 variants can be oriented in one of two ways, with respect to the spacer sequence, deemed the "A" and "B" orientations.
• orientation A the region of the gRNAs that bind the PAM motifs is distal to the spacer sequence with the 5' ends of the gRNAs adjacent to the spacer sequence ( Figure 6C); whereas in orientation B, the region of the gRNAs that bind the PAM motifs is adjacent to the spacer sequence ( Figure 9).
• the gRNAs are engineered or selected to bind (e.g.
• the gRNAs are engineered or selected to bind (e.g., as part of a complex with a Cas9 variant such as fCas9) to a target nucleic acid in the A or B orientation.
• the gRNAs are engineered or selected to bind (e.g., as part of a complex with a Cas9 variant such as fCas9) to a target nucleic acid in the A orientation.
• the gRNAs are engineered or selected to bind (e.g., as part of a complex with a Cas9 variant, such as fCas9) to a target nucleic acid in the B orientation.
• the domains of the fusion protein are linked via a linker e.g. , as described herein.
• the linker is a peptide linker.
• the linker is a non-peptidic linker.
• a functional domain is linked via a peptide linker (e.g., fused) or a non-peptidic linker to an inventive fusion protein.
• the functional domain is a nuclear localization signal (NLS) domain.
• NLS domain comprises an amino acid sequence that "tags" or signals a protein for import into the cell nucleus by nuclear transport.
• this signal consists of one or more short sequences of positively charged lysines or arginines exposed on the protein surface.
• NLS sequences are well known in the art (See e.g. , Lange et al., "Classical nuclear localization signals: definition, function, and interaction with importin alpha.” J Biol Chem. 2007 Feb 23;282(8):5101-5; the entire contents of which is hereby incorporated by reference) , and include, for example those described in the Examples section.
• the NLS sequence comprises, in part or in whole, the amino acid sequence
• the domains e.g., two or more of a gRNA binding domain (dCas9 domain), a catalytic nuclease domain, and a NLS domain
• the domains can be linked in any orientation or order.
• any domain can be at the N-terminus, the C-terminus, or in between the domains at the N- and C-termini of the fusion protein.
• the orientation or order of the domains in an inventive fusion protein are as provided in Figure 6B.
• the fusion protein comprises three domains (e.g.
• a gRNA binding domain e.g., dCas9 domain
• a nuclease domain e.g., Fokl
• an NLS domain each domain is connected via a linker, as provided herein.
• the domains are not connected via a linker.
• one or more of the domains is/are connected via a linker.
• an inventive fusion protein (e.g. , fCas9) comprising three domains (e.g., a gRNA binding domain (e.g. , dCas9 domain), a nuclease domain (e.g. , Fokl), and an NLS domain) is encoded by a nucleotide sequence (or fragment or variant thereof) set forth as SEQ ID NO:9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, or SEQ ID NO:319, as shown below.
• fCas9 e.g., dCas9-NLS-GGS31inker-FokI
• fCas9 e.g., NLS- dCas9-GGS31inker -Fokl
• fCas9 ⁇ e.g., FokI-GGS31inker-dCas9-NLS:
• fCas9 ⁇ e.g., NLS -FokI-GGS31inker-dCas9):
• an inventive fusion protein (e.g. , fCas9) corresponds to or is encoded by a homologue of any one of SEQ ID NO:9- 12 or SEQ ID NO:319.
• an inventive fusion protein (e.g. , fCas9) comprises, in part of in whole, one or more of the amino acid sequences set forth as SEQ ID NO:5, SEQ ID NO:320, SEQ ID NO:6, SEQ ID NO: 16, SEQ ID NO:318, and SEQ ID NO:321, as provided herein and shown below.
• the various domains corresponding to SEQ ID NO:5, SEQ ID NO:320, SEQ ID NO:6, SEQ ID NO: 16, SEQ ID NO:318, and SEQ ID NO:321 may be arranged in any order with respect to each other.
• a dCas9 domain (e.g., SEQ ID NO:5 or SEQ ID NO:320) is at the amino or carboxy terminus, or is somewhere in between the amino and carboxy termini.
• each of the other domains corresponding to SEQ ID NO:6, SEQ ID NO: 16, SEQ ID NO:318, and SEQ ID NO:321 may be at the amino or carboxy terminus, or somewhere in between the amino and carboxy termini of an inventive fusion protein (e.g. , fCas9).
• inventive fusion proteins having various domain arrangements include the inventive fusion proteins corresponding to SEQ ID NOs:9- 12 and SEQ ID NO:319.
• an inventive fusion protein comprises additional or other domains, such as other linkers, other NLS domains, other nuclease domains, or other Cas9 domains, which may be in addition to or substituted for any of the domains as provided herein.
• the fusion proteins forming the dimer are coordinated through the action of a single extended gRNA (e.g., as opposed to two separate gRNAs, each binding a monomer of the fusion protein dimer).
• the single extended gRNA contains at least two portions, separated by a linker sequence, that complement the target nucleic acid (e.g., bind the target nucleic acid at two distinct sites), and the gRNA is able to bind at least two fusion proteins, as described herein. This is exemplified by the schematic shown in Figure IB.
• the linker sequence separating the two portions in the extended gRNA has complementarity with the target sequence.
• the extended gRNA is at least 50, at least 60, at least 70, at least 80, at least 90, at least 100, at least 125, at least 150, at least 175, at least 200, at least 250, at least 300, at least 350, at least 400, at least 500, at least 600, at least 700, at least 800, at least 900, or at least 1000 or more nucleotides in length.
• the fusion proteins are coordinated through separate or a single gRNA, to form dimers that can cleave a target nucleic acid, it is expected that the specificity of such cleavage is enhanced (e.g., reduced or no off-target cleavage) as compared to nucleases having a single target nucleic acid binding site.
• the dimers are coordinated through the action of a single extended gRNA that comprises at least two portions that complement the target nucleic acid.
• the portions complementary to the target nucleic acid comprise no more than 25, no more than 24, no more than 23, no more than 22, no more than 21, no more than 20, no more than 19, no more than 18, no more than 17, no more than 16, no more than 15, no more than 14, no more than 13, no more than 12, no more than 11, no more than 10, no more than 9, no more than 8, no more than 7, no more than 6, or no more than 5 nucleotides that complement the target nucleic acid.
• the portions complementary to the target nucleic acid comprise 5-30, 5-25, or 5-20 nucleotides.
• the portions complementary to the target nucleic acid comprise 15-25, 19-21, or 20 nucleotides.
• the portions comprise the same number of nucleotides that
• the portions comprise different numbers of nucleotides that complement the target nucleic acid.
• the extended gRNA comprises two portions that complement (e.g. , and hybridize to) the target nucleic acid, each portion comprising 5- 19, 10- 15, or 10 nucleotides that complement the target nucleic acid.
• having the portions comprise fewer than approximately 20 nucleotides typical of gRNAs (e.g., having the portions comprise approximately 5- 19, 10- 15, or 10 complementary nucleotides), ensures that a single Cas9:gRNA unit cannot bind efficiently by itself.
• the linker sequence separating the two portions of the extended gRNA has complementarity with the target sequence.
• the linker sequence has at least 5, at least 6, at least 7, at least 8, at least 9, at least 10, at least 11, at least 12, at least 13, at least 14, at least 15, at least 20, at least 25, at least 30, at least 40, or at least 50 nucleotides that complement the target nucleic acid.
• any of the Cas9 proteins described herein may be coordinated through a single extended gRNA.
• proteins comprising a fragment of an RNA- programmable nuclease e.g., Cas9 are provided.
• a protein comprising the gRNA binding domain of Cas9 is provided.
• the protein comprising the gRNA binding domain of Cas9 does not comprise a DNA cleavage domain (referred to herein as the "A-half of Cas9).
• proteins comprising the DNA cleavage domain(s) e.g., the HNH, RuvCl subdomains
• the "DNA cleavage domain” refers collectively to the portions of Cas9 required for double- stranded DNA cleavage (e.g. , the HNH, RuvCl subdomains).
• the protein comprising the DNA cleavage domain of Cas9 does not comprise a gRNA binding domain (referred to herein as the "B-half ' of Cas9).
• dimers are provided that comprise (i) a protein comprising the gRNA binding domain of Cas9 (e.g., the A-half), and (ii) a protein comprising the DNA cleavage domain of Cas9 (e.g., the B-half).
• the dimer is bound by a gRNA.
• such dimers are expected to recapitulate the binding and cleaving activities of a full length Cas9 protein.
• dimers are referred to herein as "dimeric split Cas9.”
• dimeric split Cas9 Using a dimeric split Cas9 to cleave a target nucleic acid is expected to provide for increased specificity as compared to a single full length Cas9 protein because both halves of the protein must be co-localized to associate and re-fold into a nuclease-active state. This strategy is shown in the schematic of Figure 2A.
• fusion proteins comprising two domains are provided:
• a protein capable of specifically binding a target nucleic acid e.g. , a nuclease-inactivated RNA programmable nuclease, such as a nuclease-inactivated Cas9, as described herein
• a target nucleic acid e.g. , a nuclease-inactivated RNA programmable nuclease, such as a nuclease-inactivated Cas9, as described herein
• domain (i) of the aforementioned fusion protein comprises a DNA binding domain, for example, a DNA binding domain of a zinc finger or TALE protein.
• the fusion protein comprises (i) a nuclease- inactivated Cas9, and (ii) a gRNA binding domain of Cas9 (e.g., Cas9 A-half). In some embodiments, domain (ii) of the fusion protein does not include a DNA cleavage domain. In other embodiments, the fusion protein comprises (i) a nuclease-inactivated Cas9, and (ii) a DNA cleavage domain (e.g., Cas9 B-half). In some embodiments, domain (ii) of the fusion protein does not include a gRNA binding domain.
• dimers comprise two proteins: (i) a fusion protein comprising a nuclease-inactivated Cas9 and a gRNA binding domain of Cas9 (e.g., nuclease-inactivated Cas9 fused to Cas9 A-half), and (ii) a protein comprising the DNA cleavage domain of Cas9 (e.g. , Cas9 B-half).
• the dimer comprises (i) a fusion protein comprising a nuclease-inactivated Cas9 and a DNA cleavage domain of Cas9 (e.g., nuclease-inactivated Cas9 fused to Cas9 B-half), and (ii) a protein comprising the gRNA binding domain of Cas9 (e.g. , Cas9 A-half).
• the protein dimers include one or more gRNAs.
• the dimers include two gRNAs: one bound by the nuclease-inactivated Cas9 domain of the fusion protein; the other bound by the A-half domain (e.g., either the A-half of the fusion protein, or the A-half of the dimer not part of the fusion protein).
• a dimer e.g., associated with two gRNAs having sequences binding separate regions of a target nucleic acid
• This strategy is shown in Figure 2B.
• a protein dimer comprises two fusion proteins: (i) a fusion protein comprising a nuclease-inactivated Cas9 and a gRNA binding domain of Cas9 (e.g., a nuclease-inactivated Cas9 fused to a Cas9 A-half), and (ii) a fusion protein comprising a nuclease-inactivated Cas9 and a DNA cleavage domain (e.g. , a nuclease-inactivated Cas9 fused to a Cas9 B-half).
• the dimer is associated with (e.g., binds) one or more distinct gRNAs. For example, in some
• the dimer is associated with two or three gRNAs. In some embodiments, the dimer is associated with three gRNAs. For example, upon binding of one nuclease- inactivated Cas9:gRNA to a region of a nucleic acid target, and binding of the other nuclease- inactivated Cas9:gRNA to a second region of the nucleic acid target, the split Cas9 halves (e.g., A-half and B-half of the fusion proteins) can dimerize and bind a third gRNA complementary to a third region of the nucleic acid target, to become a fully active Cas9 nuclease, which can cleave dsDNA. This strategy is illustrated in Figure 2C.
• the split Cas9 halves e.g., A-half and B-half of the fusion proteins
• minimized Cas9 proteins are provided.
• minimized it is meant that the Cas9 protein comprises amino acid deletions and/or truncations, as compared to the wild type protein, but retains gRNA binding activity, DNA cleavage activity, or both.
• Any of the embodiments herein describing Cas9 proteins e.g., split Cas9 proteins, Cas9 A-half, Cas9 B-half, nuclease-inactivated Cas9 fusion proteins, etc.
• minimized Cas9 proteins comprising N-terminal deletions and/or truncations are provided.
• minimized Cas9 proteins comprising C-terminal deletions and/or truncations are provided. In some embodiments, minimized Cas9 proteins are provided that comprise N- and/or C-terminal deletions and/or truncations. In some embodiments, the minimized Cas9 protein retains both gRNA binding and DNA cleavage activities. In some embodiments, the minimized Cas9 protein comprises an N-terminal truncation that removes at least 5, at least 10, at least 15, at least 20, at least 25, at least 40, at least 40, at least 50, at least 75, at least 100, at least 150, at least 200, at least 250, at least 300, at least 350, at least 400, at least 450, or at least 500 amino acids.
• the minimized Cas9 protein comprises a C-terminal truncation that removes at least 5, at least 10, at least 15, at least 20, at least 25, at least 40, at least 40, at least 50, at least 75, at least 100, at least 150, at least 200, at least 250, at least 300, at least 350, at least 400, at least 450, or at least 500 amino acids.
• deletions are made within Cas9, for example in regions not affecting gRNA binding and/or DNA cleavage.
• the minimized Cas9 protein is associated with one or more gRNAs. In certain embodiments, the minimized Cas9 protein is associated with one gRNA.
• Some aspects of this disclosure provide RNA-guided recombinase fusion proteins that are designed using the methods and strategies described herein. Some embodiments of this disclosure provide nucleic acids encoding such recombinases. Some embodiments of this disclosure provide expression constructs comprising such encoding nucleic acids. For example, in some embodiments an isolated recombinase is provided that has been engineered to recombine a desired target site ⁇ e.g., a site targeted by one or more gRNAs bound to one or more of the engineered recombinases) within a genome, e.g., with another site in the genome or with an exogenous nucleic acid.
• a desired target site e.g., a site targeted by one or more gRNAs bound to one or more of the engineered recombinases
• the isolated recombinase comprises a variant of an RNA-programmable nuclease, such as a Cas9 nuclease.
• the Cas9 variant is a nuclease-inactivated Cas9 ⁇ e.g., dCas9).
• dCas9 is encoded by a nucleotide sequence comprising in part or in whole, SEQ ID NO:5 or SEQ ID NO:320.
• dCas9 is encoded by a nucleotide sequence comprising a variant of SEQ ID NO:5 or SEQ ID NO:320.
• an RNA-guided recombinase fusion protein is provided.
• the fusion protein comprises two or more domains.
• the fusion protein comprises two domains.
• one of the two or more domains is a nuclease-inactivated Cas9 (or fragment thereof, e.g., Cas9 A-half), for example, those described herein ⁇ e.g., dCas9).
• the Cas9 domain of the recombinase fusion protein is capable of binding one or more gRNAs, and thereby directs or targets the recombinase fusion protein(s) to a target nucleic acid, e.g., as described herein.
• Another domain of the two or more domains is a recombinase, or a fragment thereof, e.g. , a catalytic domain of a recombinase.
• catalytic domain of a recombinase it is meant that a fusion protein includes a domain comprising an amino acid sequence of (e.g. , derived from) a recombinase, such that the domain is sufficient to induce recombination when contacted with a target nucleic acid (either alone or with additional factors including other recombinase catalytic domains which may or may not form part of the fusion protein).
• a catalytic domain of a recombinase excludes a DNA binding domain of the recombinase.
• the catalytic domain of a recombinase includes part or all of a recombinase, e.g., the catalytic domain may include a recombinase domain and a DNA binding domain, or parts thereof, or the catalytic domain may include a recombinase domain and a DNA binding domain that is mutated or truncated to abolish DNA binding activity.
• Recombinases and catalytic domains of recombinases are known to those of skill in the art, and include, for example, those described herein.
• the catalytic domain is derived from any recombinase.
• the recombinase catalytic domain is a catalytic domain of aTn3 resolvase, a Hin recombinase, or a Gin recombinase.
• the catalytic domain comprises a Tn3 resolvase (e.g., Stark Tn3 recombinase) that is encoded by a nucleotide sequence comprising, in part or in whole, SEQ ID NO:322, as provided below.
• a Tn3 catalytic domain is encoded by a variant of SEQ ID NO:322.
• a Tn3 catalytic domain is encoded by a
• the catalytic domain comprises a Hin recombinase that is encoded by a nucleotide sequence comprising, in part or in whole, SEQ ID NO:323, as provided below.
• a Hin catalytic domain is encoded by a variant of SEQ ID NO:323.
• a Hin catalytic domain is encoded by a
• the catalytic domain comprises a Gin recombinase (e.g. , Gin beta recombinase) that is encoded by a nucleotide sequence comprising, in part or in whole, SEQ ID NO:324, as provided below.
• a Gin catalytic domain is encoded by a variant of SEQ ID NO:324.
• a Gin catalytic domain is encoded by a polynucleotide (or a variant thereof) that encodes the polypeptide
• Gin beta recombinase (nucleotide: SEQ ID NO:324; amino acid: SEQ ID NO:324; amino acid: SEQ ID NO:
• the recombinase catalytic domain is fused to the N- terminus, the C-terminus, or somewhere in between the N- and C-termini of a Cas9 protein (e.g., sCas9).
• the fusion protein further comprises a nuclear localization signal (NLS; e.g. , any of those provided herein).
• NLS nuclear localization signal
• the general architecture of exemplary RNA-guided recombinase fusion proteins (e.g. , Cas9-recombinase fusions) comprise one of the following structures: [NH 2 ] - [Cas9] - [recombinase] - [COOH] ,
• a linker is inserted between the Cas9 domain and the recombinase domain, e.g., any linker provided herein. Additional features, such as sequence tags (e.g., any of those provided herein), may also be present.
• any of the nucleases e.g., fusion proteins comprising nucleases or nuclease domains
• recombinases e.g., fusion proteins comprising recombinases or recombinase catalytic domains
• pharmaceutical compositions comprising a nuclease and/or recombinase as provided herein, or a nucleic acid encoding such a nuclease and/or recombinase, and a pharmaceutically acceptable excipient.
• Pharmaceutical compositions may optionally comprise one or more additional therapeutically active substances.
• compositions provided herein are administered to a subject, for example, to a human subject, in order to effect a targeted genomic modification within the subject.
• cells are obtained from the subject and are contacted with a nuclease and/or recombinase ex vivo.
• cells removed from a subject and contacted ex vivo with an inventive nuclease and/or recombinase are reintroduced into the subject, optionally after the desired genomic modification has been effected or detected in the cells.
• compositions are generally suitable for administration to animals of all sorts. Modification of pharmaceutical compositions suitable for administration to humans in order to render the compositions suitable for administration to various animals is well understood, and the ordinarily skilled veterinary pharmacologist can design and/or perform such modification with merely ordinary, if any, experimentation.
• Subjects to which administration of the pharmaceutical compositions is contemplated include, but are not limited to, humans and/or other primates; mammals, domesticated animals, pets, and commercially relevant mammals such as cattle, pigs, horses, sheep, cats, dogs, mice, and/or rats; and/or birds, including commercially relevant birds such as chickens, ducks, geese, and/or turkeys.
• Formulations of the pharmaceutical compositions described herein may be prepared by any method known or hereafter developed in the art of pharmacology. In general, such preparatory methods include the step of bringing the active ingredient into association with an excipient, and then, if necessary and/or desirable, shaping and/or packaging the product into a desired single- or multi-dose unit.
• compositions may additionally comprise a pharmaceutically acceptable excipient, which, as used herein, includes any and all solvents, dispersion media, diluents, or other liquid vehicles, dispersion or suspension aids, surface active agents, isotonic agents, thickening or emulsifying agents, preservatives, solid binders, lubricants and the like, as suited to the particular dosage form desired.
• a pharmaceutically acceptable excipient includes any and all solvents, dispersion media, diluents, or other liquid vehicles, dispersion or suspension aids, surface active agents, isotonic agents, thickening or emulsifying agents, preservatives, solid binders, lubricants and the like, as suited to the particular dosage form desired.
• Remington's The Science and Practice of Pharmacy 21 st Edition, A. R. Gennaro (Lippincott, Williams & Wilkins, Baltimore, MD, 2006; incorporated in its entirety herein by reference) discloses various excipient
• compositions in accordance with the present invention may be used for treatment of any of a variety of diseases, disorders, and/or conditions, including but not limited to one or more of the following: autoimmune disorders ⁇ e.g.
• diabetes diabetes, lupus, multiple sclerosis, psoriasis, rheumatoid arthritis
• inflammatory disorders ⁇ e.g. arthritis, pelvic inflammatory disease
• infectious diseases ⁇ e.g. viral infections ⁇ e.g., HIV, HCV, RSV), bacterial infections, fungal infections, sepsis
• neurological disorders ⁇ e.g. Alzheimer's disease, Huntington's disease; autism; Duchenne muscular dystrophy
• cardiovascular disorders e.g. atherosclerosis, hypercholesterolemia, thrombosis, clotting disorders, angiogenic disorders such as macular degeneration
• proliferative disorders e.g. cancer, benign neoplasms
• respiratory disorders e.g.
• chronic obstructive pulmonary disease e.g. inflammatory bowel disease, ulcers); musculoskeletal disorders (e.g. fibromyalgia, arthritis); endocrine, metabolic, and nutritional disorders (e.g. diabetes, osteoporosis); urological disorders (e.g. renal disease); psychological disorders (e.g. depression, schizophrenia); skin disorders (e.g. wounds, eczema); blood and lymphatic disorders (e.g. anemia, hemophilia); etc.
• digestive disorders e.g. inflammatory bowel disease, ulcers
• musculoskeletal disorders e.g. fibromyalgia, arthritis
• endocrine, metabolic, and nutritional disorders e.g. diabetes, osteoporosis
• urological disorders e.g. renal disease
• psychological disorders e.g. depression, schizophrenia
• skin disorders e.g. wounds, eczema
• blood and lymphatic disorders e.g. anemia, hemophilia
• methods for site-specific nucleic acid (e.g., DNA) cleavage comprise contacting a DNA with any of the Cas9:gRNA complexes described herein.
• the method comprises contacting a DNA with a fusion protein (e.g., fCas9) that comprises two domains: (i) a nuclease-inactivated Cas9 (dCas9); and (ii) a nuclease (e.g., a Fokl DNA cleavage domain), wherein the wherein the inactive Cas9 domain binds a gRNA that hybridizes to a region of the DNA.
• a fusion protein e.g., fCas9
• dCas9 nuclease-inactivated Cas9
• a nuclease e.g., a Fokl DNA cleavage domain
• the method further comprises contacting the DNA with a second fusion protein described herein (e.g., fCas9), wherein the nuclease-inactivated Cas9 (dCas9) domain of the second fusion protein binds a second gRNA that hybridizes to a second region of DNA, wherein the binding of the fusion proteins results in the dimerization of the nuclease domains of the fusion proteins, such that the DNA is cleaved in a region between the bound fusion proteins. See e.g., Figures 1A, 6D.
• the gRNAs bound to each fusion protein hybridize to the same strand of the DNA, or they hybridize to opposing strands of the DNA.
• the gRNAs hybridize to regions of the DNA that are no more than 10, no more than 15, no more than 20, no more than 25, no more than 30, no more than 40, 50, no more than 60, no more than 70, no more than 80, no more than 90, or no more than 100 base pairs apart.
• the region between the bound Cas9:gRNA complexes may be referred to as the "spacer sequence," which is typically where the target nucleic acid is cleaved. See, e.g., Figures 6C-D.
• the spacer sequence is at least 5, at least 10, at least 15, at least 20, at least 25, at least 30 at least 35, at least 40, at least 45, at least 50, at least 60, at least 70, at least 80, at least 90, or at least 100 base pairs in length. In some embodiments, the spacer sequence is between about 5 and about 50 base pairs, about 10 and about 40, or about 15 and about 30 base pairs in length. In some embodiments, the spacer sequence is about 15 to about 25 base pairs in length. In some embodiments, the spacer sequence is about 15, about 20, or about 25 base pairs in length. In some embodiments, the Cas9:gRNA complexes are bound in the A orientation, as described herein.
• the Cas9:gRNA complexes are bound in the B orientation, as described herein.
• the method has an on-target:off-target modification ratio that is at least 2-fold, at least 5-fold, at least 10-fold, at least 20-fold, at least 30-fold, at least 40-fold, at least 50- fold, at least 60-fold, at least 70-fold, at least 80-fold, at least 90-fold, at least 100-fold, at least 110-fold, at least 120-fold, at least 130-fold, at least 140-fold, at least 150-fold, at least 175-fold, at least 200-fold, or at least 250-fold or more higher than the on-target:off-target modification ratio of methods utilizing a wild type Cas9 or other Cas9 variant.
• the method has an on-target:off-target modification ratio that is between about 60- to about 180-fold, between about 80- to about 160-fold, between about 100- to about 150- fold, or between about 120- to about 140-fold higher than the on-target:off-target
• the fusion proteins are coordinated or associated through a single gRNA, e.g., as described herein.
• the method comprises contacting a nucleic acid with a dimer of Cas9 proteins (or fragments thereof) coordinated with (e.g., bound by) a single gRNA as described herein.
• the single gRNA comprises at least two portions that hybridize to the nucleic acid.
• the portions comprise at least 5, at least 10, at least 15, or at least 19 complementary nucleotides.
• the portions comprise fewer than 20 complementary nucleotides.
• a linker sequence separates the portions, wherein the linker sequence also comprises nucleotides complementary to the target nucleic acid (e.g. , but are not bound by a Cas9 protein). In some embodiments, the linker sequence does not hybridize to the target nucleic acid.
• the methods comprise contacting a DNA with a protein dimer of fusion proteins described herein, wherein the fusion proteins are bound by one or more gRNAs.
• one fusion protein of the dimer comprises a gRNA binding domain of Cas9 (e.g., Cas9 A-half), wherein the protein does not comprise a DNA cleavage domain (e.g., Cas9 B-half); and the other fusion protein of the dimer comprises a DNA cleavage domain of Cas9 (e.g., Cas9 B-half), wherein the protein does not comprise a gRNA binding domain (e.g. , Cas9 A-half).
• the binding of a gRNA (e.g., that hybridizes to a target nucleic acid) to one or both of the monomers of the dimer co-localizes the dimer to the target nucleic acid, allowing the dimer to re-fold into a nuclease- active state and cleave the target nucleic acid.
• the method comprises contacting a nucleic acid with protein dimers comprising two proteins: (i) a fusion protein comprising a nuclease- inactivated Cas9 and a gRNA binding domain of Cas9 (e.g. , nuclease-inactivated Cas9 fused to Cas9 A-half), and (ii) a protein comprising the DNA cleavage domain of Cas9 (e.g. , Cas9 B-half).
• the dimer comprises (i) a fusion protein comprising a nuclease-inactivated Cas9 and a DNA cleavage domain of Cas9 (e.g.
• nuclease-inactivated Cas9 fused to Cas9 B-half nuclease-inactivated Cas9 fused to Cas9 B-half
• a protein comprising the gRNA binding domain of Cas9 e.g., Cas9 A-half
• the protein dimers are associated with one or more gRNAs.
• the dimers are associated with two gRNAs: one bound by the nuclease-inactivated Cas9 domain of the fusion protein; the other bound by the A-half domain (e.g., either the A-half of the fusion protein, or the A-half of the dimer not part of the fusion protein).
• the protein dimer comprises (i) a fusion protein comprising a nuclease-inactivated Cas9 and a gRNA binding domain of Cas9 (e.g., a nuclease-inactivated Cas9 fused to a Cas9 A-half), and (ii) a fusion protein
• the dimer is associated with one or more distinct gRNAs.
• the dimer is associated with two or three gRNAs. In some embodiments, the dimer is associated with three gRNAs.
• the split Cas9 halves dimerize and bind a third gRNA complementary to a third region of the nucleic acid target, to become a fully active Cas9 nuclease leading to cleave of the target DNA.
• a method for site-specific cleavage of a nucleic acid comprises contacting a nucleic acid (e.g., DNA) with a minimized Cas9 protein (e.g. , as described herein) associated with a gRNA.
• a nucleic acid e.g., DNA
• a minimized Cas9 protein e.g. , as described herein
• any of the methods provided herein can be performed on DNA in a cell, for example a bacterium, a yeast cell, or a mammalian cell.
• the DNA contacted by any Cas9 protein provided herein is in a eukaryotic cell.
• the methods can be performed on a cell or tissue in vitro or ex vivo.
• the eukaryotic cell is in an individual, such as a patient or research animal. In some embodiments, the individual is a human.
• methods for site-specific nucleic acid ⁇ e.g., DNA recombination are provided.
• the methods are useful for inducing recombination of or between two or more regions of two or more nucleic acid ⁇ e.g., DNA) molecules.
• the methods are useful for inducing recombination of or between two or more regions in a single nucleic acid molecule ⁇ e.g., DNA).
• the recombination of one or more target nucleic acid molecules requires the formation of a tetrameric complex at the target site.
• the tetramer comprises four (4) inventive RNA-guided recombinase fusion proteins ⁇ e.g., a complex of any four inventive recombinase fusion protein provided herein).
• each recombinase fusion protein of the tetramer targets a particular DNA sequence via a distinct gRNA bound to each recombinase fusion protein (See, e.g., Figure 5).
• the method for site- specific recombination between two DNA molecules comprises (a) contacting a first DNA with a first RNA-guided recombinase fusion protein, wherein the nuclease-inactivated Cas9 domain binds a first gRNA that hybridizes to a region of the first DNA; (b) contacting the first DNA with a second RNA-guided recombinase fusion protein, wherein the nuclease-inactivated Cas9 domain of the second fusion protein binds a second gRNA that hybridizes to a second region of the first DNA; (c) contacting a second DNA with a third RNA-guided recombinase fusion protein, wherein the nuclease-inactivated Cas9 domain of the third fusion protein binds a third gRNA that hybridizes to a region of the second DNA; and (d) contacting the second DNA with a fourth RNA-guided recombinase
• steps (a) - (d) results in the tetramerization of the recombinase catalytic domains of the fusion proteins, such that the DNAs are recombined.
• the gRNAs of steps (a) and (b) hybridize to opposing strands of the first DNA
• the gRNAs of steps (c) and (d) hybridize to opposing strands of the second DNA.
• the target sites of the gRNAs of steps (a) - (d) are spaced to allow for tetramerization of the recombinase catalytic domains.
• the target sites of the gRNAs of steps (a) - (d) are no more than 10, no more 15, no more than 20, no more than 25, no more than 30, no more than 40, no more than 50, no more than 60, no more than 70, no more than 80, no more than 90, or no more than 100 base pairs apart.
• the two regions of the two DNA molecules being recombined share homology, such that the regions being recombined are at least 80%, at least 90%, at least 95%, at least 98%, or are 100% homologous.
• the methods comprise (a) contacting a DNA with a first RNA-guided recombinase fusion protein, wherein the nuclease-inactivated Cas9 domain binds a first gRNA that hybridizes to a region of the DNA; (b) contacting the DNA with a second RNA-guided recombinase fusion protein, wherein the nuclease-inactivated Cas9 domain of the second fusion protein binds a second gRNA that hybridizes to a second region of the DNA; (c) contacting the DNA with a third RNA-guided recombinase fusion protein, wherein the nuclease-inactivated Cas9 domain of the third fusion protein binds a third gRNA that hybridizes to a third region of the DNA; and (d) contacting the DNA with
• steps (a) - (d) results in the tetramerization of the recombinase catalytic domains of the fusion proteins, such that the DNA is recombined.
• two of the gRNAs of steps (a) - (d) hybridize to the same strand of the DNA, and the other two gRNAs of steps (a)- (d) hybridize to the opposing strand of the DNA.
• the gRNAs of steps (a) and (b) hybridize to regions of the DNA that are no more 10, no more than 15, no more than 20, no more than 25, no more than 30, no more than 40, no more than 50, no more than 60, no more than 70, no more than 80, no more than 90, or no more than 100 base pairs apart, and the gRNAs of steps (c) and (d) hybridize to regions of the DNA that are no more than 10, no more 15, no more than 20, no more than 25, no more than 30, no more than 40, no more than 50, no more than 60, no more than 70, no more than 80, no more than 90, or no more than 100 base pairs apart.
• the two regions of the DNA molecule being recombined share homology, such that the regions being recombined are at least 80%, at least 90%, at least 95%, at least 98%, or are 100% homologous.
• any of the inventive methods for site-specific recombination are amenable for inducing recombination, such that the recombination results in excision (e.g., a segment of DNA is excised from a target DNA molecule), insertion (e.g. , a segment of DNA is inserted into a target DNA molecule), inversion (e.g. , a segment of DNA is inverted in a target DNA molecule), or translocation (e.g., the exchange of DNA segments between one or more target DNA molecule(s)).
• excision e.g., a segment of DNA is excised from a target DNA molecule
• insertion e.g. , a segment of DNA is inserted into a target DNA molecule
• inversion e.g. , a segment of DNA is inverted in a target DNA molecule
• translocation e.g., the exchange of DNA segments between one or more target DNA molecule(s)
• the particular recombination event depends, inter alia, on the orientation (e.g., with respect to the target DNA molecule(s)) of the bound RNA-guided recombinase fusion protein(s).
• the orientation, or direction, in which a RNA-guided recombinase fusion protein binds a target nucleic acid can be controlled, e.g., by the particular sequence of the gRNA bound to the RNA-guided recombinase fusion protein(s).
• any of the methods for site-specific recombination can be performed in vivo or in vitro. In some embodiments, any of the methods for site-specific recombination are performed in a cell (e.g., recombine genomic DNA in a cell).
• the cell can be prokaryotic or eukaryotic.
• the cell such as a eukaryotic cell, can be in an individual, such as a subject, as described herein (e.g., a human subject).
• a cell obtained from a subject and modified according to the methods provided herein is re-introduced into a subject (e.g., the same subject), e.g., to treat a disease, or for the production of genetically modified organisms in agriculture or biological research.
• a nucleic acid comprising a donor sequence to be inserted is also provided, e.g., to a cell.
• a donor sequence it is meant a nucleic acid sequence to be inserted at the target site induced by one or more RNA- guided recombinase fusion protein(s).
• the donor sequence will share homology to a genomic sequence at the target site, e.g., 1%, 2%, 3%, 4%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 85%, 90%, 95%, or 100% homology with the nucleotide sequences flanking the target site, e.g., within about 100 bases or less of the target site, e.g. within about 90 bases, within about 80 bases, within about 70 bases, within about 60 bases, within about 50 bases, within about 40 bases, within about 30 bases, within about 15 bases, within about 10 bases, within about 5 bases, or immediately flanking the target site.
• the donor sequence does not share any homology with the target nucleic acid, e.g., does not share homology to a genomic sequence at the target site.
• Donor sequences can be of any length, e.g., 10 nucleotides or more, 50 nucleotides or more, 100 nucleotides or more, 250 nucleotides or more, 500 nucleotides or more, 1000 nucleotides or more, 5000 nucleotides or more, 10000 nucleotides or more, 100000 nucleotides or more, etc.
• the donor sequence is not identical to the target sequence that it replaces or is inserted into.
• the donor sequence contains at least one or more single base changes, insertions, deletions, inversions or rearrangements with respect to the target sequence ⁇ e.g., target genomic sequence).
• donor sequences also comprise a vector backbone containing sequences that are not homologous to the DNA region of interest and that are not intended for insertion into the DNA region of interest.
• the donor sequence may comprise certain sequence differences as compared to the target ⁇ e.g., genomic) sequence, for example restriction sites, nucleotide
• polymorphisms selectable markers ⁇ e.g., drug resistance genes, fluorescent proteins, enzymes etc.
• selectable markers e.g., drug resistance genes, fluorescent proteins, enzymes etc.
• these sequences differences may include flanking recombination sequences such as FLPs, loxP sequences, or the like, that can be activated at a later time for removal of e.g., a marker sequence.
• the donor sequence may be provided to the cell as single- stranded DNA, single- stranded RNA, double- stranded DNA, or double- stranded RNA. It may be introduced into a cell in linear or circular form. If introduced in linear form, the ends of the donor sequence may be protected ⁇ e.g., from exonucleolytic degradation) by methods known to those of skill in the art. For example, one or more dideoxynucleotide residues are added to the 3' terminus of a linear molecule and/or self-complementary oligonucleotides are ligated to one or both ends. See, e.g., Chang et ah, Proc. Natl. Acad Sci USA.
• a donor sequence can be introduced into a cell as part of a vector molecule having additional sequences such as, for example, replication origins, promoters and genes encoding antibiotic resistance.
• donor sequences can be introduced as naked nucleic acid, as nucleic acid complexed with an agent such as a liposome or poloxamer, or can be delivered by viruses (e.g., adenovirus, AAV, etc.).
• polynucleotides encoding one or more of the inventive proteins and/or gRNAs are provided.
• polynucleotides encoding any of the proteins described herein are provided, e.g., for recombinant expression and purification of isolated nucleases and recombinases, e.g., comprising Cas9 variants.
• an isolated polynucleotide comprises one or more sequences encoding a Cas9 half site (e.g., A-half and/or B-half).
• an isolated polynucleotide comprises one or more sequences encoding a Cas9 fusion protein, for example, any of the Cas9 fusion proteins described herein (e.g., those comprising a nuclease-inactivated Cas9).
• an isolated polynucleotides comprises one or more sequences encoding a gRNA, alone or in combination with a sequence encoding any of the proteins described herein.
• vectors encoding any of the proteins described herein are provided, e.g., for recombinant expression and purification of Cas9 proteins, and/or fusions comprising Cas9 proteins (e.g., variants).
• the vector comprises or is engineered to include an isolated polynucleotide, e.g., those described herein.
• the vector comprises one or more sequences encoding a Cas9 protein (as described herein), a gRNA, or combinations thereof, as described herein.
• the vector comprises a sequence encoding an inventive protein operably linked to a promoter, such that the fusion protein is expressed in a host cell.
• cells are provided, e.g., for recombinant expression and purification of any of the Cas9 proteins provided herein.
• the cells include any cell suitable for recombinant protein expression, for example, cells comprising a genetic construct expressing or capable of expressing an inventive protein (e.g., cells that have been transformed with one or more vectors described herein, or cells having genomic
• kits comprising a Cas9 variant and/or nuclease and/or recombinase, as provided herein.
• the kit comprises a polynucleotide encoding an inventive Cas9 variant, nuclease, and/or recombinase, e.g., as provided herein.
• the kit comprises a vector for recombinant protein expression, wherein the vector comprises a polynucleotide encoding any of the proteins provided herein.
• the kit comprises a cell (e.g., any cell suitable for expressing Cas9 proteins or fusions comprising Cas9 proteins, such as bacterial, yeast, or mammalian cells) that comprises a genetic construct for expressing any of the proteins provided herein.
• any of the kits provided herein further comprise one or more gRNAs and/or vectors for expressing one or more gRNAs.
• the kit comprises an excipient and instructions for contacting the nuclease and/or
• the composition is suitable for delivering a Cas9 protein to a cell.
• the composition is suitable for delivering a Cas9 protein to a subject.
• the excipient is a pharmaceutically acceptable excipient.
• PCR was performed with 0.4 ⁇ L ⁇ of 2 ⁇ / ⁇ Phusion Hot Start Flex DNA polymerase (NEB) in 50 with lx HF Buffer, 0.2 mM dNTP mix (0.2 mM dATP, 0.2 mM dCTP, 0.2 mM dGTP, 0.2 mM dTTP) (NEB), 0.5 ⁇ of each primer and a program of: 98 °C, 1 min; 35 cycles of [98 °C, 15 s; 65 °C, 15 s; 72 °C, 30 s] unless otherwise noted.
• NEB Phusion Hot Start Flex DNA polymerase
• the human codon- optimized streptococcus pyogenes Cas9 nuclease with NLS and 3xFLAG tag (Addgene plasmid 43861) was used as the wild-type Cas9 expression plasmid.
• PCR (72 °C, 3 min) products of wild-type Cas9 expression plasmid as template with Cas9_Exp primers listed in Table 1 below were assembled with Gibson Assembly Cloning Kit (New England Biolabs) to construct Cas9 and i3 ⁇ 4M-dCas9 variants.
• Expression plasmids encoding a single gRNA construct (gRNA Gl through G13) were cloned as previously described.
• gRNA oligonucleotides listed in Table 1 containing the 20-bp protospacer target sequence were annealed and the resulting 4-bp overhangs were ligated into BsmBI-digested gRNA expression plasmid.
• gRNA expression plasmids encoding expression of two separate gRNA constructs from separate promoters on a single plasmid were cloned in a two-step process.
• gRNA El, VI, CI, C3, HI, Gl, G2 or G3 was cloned as above and used as template for PCR (72 °C, 3 min) with PCR_Pla-fwd and PCR_Pla-rev primers, 1 ⁇ Dpnl (NEB) was added, and the reaction was incubated at 37 °C for 30 min and then subjected to QIAquick PCR Purification Kit (Qiagen) for the "1 st gRNA + vector DNA".
• PCR 72 °C, 3 min of 100 pg of BsmBI-digested gRNA expression plasmid as template with PCR_gRN A-f wd 1 , PCR_gRNA-rev 1 , PCR_gRNA-rev2 and appropriate PCR_gRNA primer listed in Table 1 was Dpnl treated and purified as above for the "2 nd gRNA instert DNA".
• Cas9_Exp_CNF_(Cas9)NL TTGGGATCCAGAACCTCC GCTGCCGCCACTTCCACCTGA
• Cas9_Exp_NCF_PlasS+FL TAGGGAGAGCCGCCACCATGGACTACAAAGACCATGACGG (SEQ ID AG(NLS-Fokl -Rev NO:37)
• Cas9_Exp_NCF_NLS TAAACCAATAGAATACTTTTTATC CATAGGTACCCCGCGGTGAATG +Cas9coD10-Rev (SEQ ID NO:38)
• PCR_gRNA_G4 TCGTCCTTTCCA (SEQ ID NO: 102)
• PCR_gRNA_G5 TCGTCCTTTCCA (SEQ ID NO: 103)
• PCR_gRNA_G6 TCGTCCTTTCCA (SEQ ID NO: 104)
• PCR_gRNA_G7 TCGTCCTTTCCA (SEQ ID NO: 105)
• PCR_gRNA_H2 TCGTCCTTTCCA (SEQ ID NO: 1 10)
• PCR_gRNA_H7 TCGTCCTTTCCA (SEQ ID NO: 115)
• PCR_gRNA_V3 TTCGTCCTTTCCA (SEQ ID NO: 117)
• PCR_gRNA_V4 TCGTCCTTTCCA (SEQ ID NO: 118)
• HTS_EXM_Off2-fwd TTTTGTGGCTTGGCCCCAGT (SEQ ID NO: 131)
• HTS_EXM_Off3-fwd TGCAGTCTCATGACTTGGCCT (SEQ ID NO: 132)
• HTS_EXM_Off4-fwd TTCTGAGGGCTGCTACCTGT (SEQ ID NO: 133)
• HTS_EXM_Off2-fwd CCCGCCACAGTCGTGTCAT (SEQ ID NO: 136)
• HTS_EXM_Off3-fwd CGCCCCGGTACAAGGTGA (SEQ ID NO: 137)
• HTS_EXM_Off4-fwd GTACCGTACATTGTAGGATGTTT (SEQ ID NO: 138)
• HTS_CLTA2_ON-fwd CCTCATCTCCCTCAAGCAGGC (SEQ ID NO: 139)
• HTS_CLTA2_Off 1 -fwd ATTCTGCTCTTGAGGTTATTTGT SEQ ID NO: 140
• HTS_CLTA2_Off3-fwd TGTGTGTGTGTGTGTGTGTAGGACT SEQ ID NO: 142
• HTS_EXM_Off-rev CGGGAGCTGTTCAGAGGCTG (SEQ ID NO: 145)
• HTS_EXM_Offl-rev ACAGGCATGAATCACTGCACCT (SEQ ID NO: 149)
• HTS_EXM_Off2-rev GCGGCAACTTCAGACAACCGA (SEQ ID NO: 150)
• HTS_CLTA2_ON-rev ACAGTTGAAGGAAGGAAACATGC (SEQ ID NO: 153)
• HEK293-GFP stable cells were used as a cell line constitutively expressing an Emerald GFP gene (GFP) integrated on the genome.
• Cells were maintained in Dulbecco's modified Eagle medium (DMEM, Life Technologies) supplemented with 10% (vol/vol) fetal bovine serum (FBS, Life Technologies) and penicillin/streptomycin (lx, Amresco). 5 x 10 4 HEK293-GFP cells were plated on 48-well collagen coated Biocoat plates (Becton Dickinson). One day following plating, cells at -75% confluence were transfected with Lipofecatmine 2000 (Life Technologies) according to the manufacturer's protocol.
• DMEM Dulbecco's modified Eagle medium
• FBS fetal bovine serum
• lx penicillin/streptomycin
• transfection control 3.5 days following transfection, cells were trypsinized and resuspended in DMEM supplemented with 10% FBS and analyzed on a C6 flow cytometer (Accuri) with a 488 nm laser excitation and 520 nm filter with a 20 nm band pass. For each sample, transfections and flow cytometry measurements were performed once.
• HEK293-GFP stable cells were transfected with Cas9 expression and gRNA expression plasmids as described above. A single plasmid encoding two separate gRNAs was transfected. For experiments titrating the total amount of expression plasmids (Cas9 expression + gRNA expression plasmid), 700/250, 350/125, 175/62.5, 88/31 ng of Cas9 expression plasmid/ng of gRNA expression plasmid were combined with inert carrier plasmid, pUC19 (NEB), as necessary to reach a total of 950 ng transfected plasmid DNA.
• inert carrier plasmid pUC19
• Genomic DNA was isolated from cells 2 days after transfection using a genomic DNA isolation kit, DNAdvance Kit (Agencourt). Briefly, cells in a 48-well plate were incubated with 40 ⁇ ⁇ of tryspin for 5 min at 37 °C. 160 uL of DNAdvance lysis solution was added and the solution incubated for 2 hr at 55 °C and the subsequent steps in the Agencourt DNAdvance kit protocol were followed. 40 ng of isolated genomic DNA was used as template to PCR amplify the targeted genomic loci with flanking Survey primer pairs specified in Table 1.
• PCR products were purified with a QIAquick PCR Purification Kit (Qiagen) and quantified with Quant- iTTM PicoGreen ® dsDNA Kit (Life Technologies). 250ng of purified PCR DNA was combined with 2 of NEBuffer 2 (NEB) in a total volume of 19 ⁇ ⁇ and denatured then re-annealed with thermocycling at 95 °C for 5 min, 95 to 85 °C at 2 °C/s; 85 to 20 °C at 0.2 °C/s. The re-annealed DNA was incubated with 1 ⁇ of T7 Endonuclease 1 (10 U/ ⁇ , NEB) at 37 °C for 15 min.
• NEBuffer 2 NEBuffer 2
• HEK293-GFP stable cells were transfected with Cas9 expression and gRNA expression plasmids, 700 ng of Cas9 expression plasmid plus 250 ng of a single plasmid expression a pair of gRNAs were transfected (high levels) and for just Cas9 nuclease, 88 ng of Cas9 expression plasmid plus 31 ng of a single plasmid expression a pair of gRNAs were transfected (low levels). Genomic DNA was isolated as above and pooled from three biological replicates. 150 ng or 600 ng of pooled genomic DNA was used as template to amplify by PCR the on-target and off-target genomic sites with flanking HTS primer pairs specified in Table 1.
• Relative amounts of crude PCR products were quantified by gel electrophoresis and samples treated with different gRNA pairs or Cas9 nuclease types were separately pooled in equimolar concentrations before purification with the QIAquick PCR Purification Kit (Qiagen).
• Qiagen QIAquick PCR Purification Kit
• -500 ng of pooled DNA was run a 5% TBE 18- well Criterion PAGE gel (BioRad) for 30 min at 200 V and DNAs of length -125 bp to -300 bp were isolated and purified by QIAquick PCR Purification Kit (Qiagen).
• Purified DNA was PCR amplified with primers containing sequencing adaptors, purified and sequenced on a MiSeq high-throughput DNA sequencer (Illumina) as described previously. 1
• Patmatch program 38 was used to search the human genome
• GRCh37/hgl9 build for pattern sequences corresponding to Cas9 binding sites (CCN N 20 spacer N 20 NGG for Orientation A and N 20 NGG spacer CCN N 20 for Orientation B).
• the steps for the identification of ingels in sequences of genomic sites can be found below:
• flanking genomic sequences were searched for with the Patmatch program 38 allowing for varying amounts of bases from 1 to 300 between the flanking genomic sequences (Table 2):
• VEG_On (SEQIDNO:172) (SEQIDNO:173)
• VEG_Offl (SEQIDNO:174) (SEQIDNO:175)
• VEG_Off2 (SEQIDNO:176) (SEQIDNO:177)
• VEG_Off3 (SEQIDNO:178) (SEQIDNO:179)
• VEG_Off4 (SEQIDNO:180) (SEQIDNO:181)
• CLT2_Off3 (SEQIDNO:188) (SEQIDNO:189) [00160] Any target site sequences corresponding to the same size as the reference genomic site in the human genome (GRCh37/hgl9 build) were considered unmodified and any sequences not the reference size were considered potential insertions or deletions.
• Sequences not the reference size were aligned with ClustalW to the reference genomic site. Aligned sequences with more than one insertion or one deletion in the DNA spacer sequence in or between the two half-site sequences were considered indels. Since high-throughput sequencing can result in insertions or deletions of one base pairs (mis-phasing) at a low but relevant rates - indels of two bp are more likely to arise from Cas9 induced modifications.
• CLTA on-target and previously reported genomic off-target sites amplified from 150 ng genomic DNA isolated from human cells treated with a plasmid expressing either wild-type Cas9, Cas9 nickase, or fCas9 and a single plasmid expressing two gRNAs targeting the CLTA on-target site (gRNA C3 and gRNA C4).
• gRNA C3 and gRNA C4 As a negative control, transfection and sequencing were performed as above, but using two gRNAs targeting the GFP gene on-target site (gRNA Gl, G2 or G3 and gRNA G4, G5, G6 or G7.
• Indels the number of observed sequences containing insertions or deletions consistent with any of the three Cas9 nuclease-induced cleavage.
• Total total number of sequence counts while only the first 10,000 sequences were analyzed for the on-target site sequences. Modified: number of indels divided by total number of sequences as percentages. Upper limits of potential modification were calculated for sites with no observed indels by assuming there is less than one indel then dividing by the total sequence count to arrive at an upper limit modification percentage, or taking the theoretical limit of detection (1/49,500), whichever value was larger.
• P-values For wild-type Cas9 nuclease, Cas9 nickase or fCas9 nuclease, P-values were calculated as previously reported 18 using a two-sided Fisher's exact test between each sample treated with two gRNAs targeting the CLTA on-target site and the control sample treated with two gRNAs targeting the GFP on-target site. P-values of ⁇ 0.0045 were considered significant and shown based on conservative multiple comparison correction using the Bonferroni method. On:off specificity is the ratio of on-target to off-target genomic modification frequency for each site.
• (B) Shows experimental and analytic methods as in (A) applied to EMX target sites using a single plasmid expressing two gRNAs targeting the EMX on-target site (gRNA El and gRNA E2).
• (C) shows experimental and analytic methods as in (A) applied to VEGF target sites using a single plasmid expressing two gRNAs targeting the VEGF on-target site (gRNA VI and gRNA v2).
• (D) shows experimental and analytic methods as in (A) applied to VEGF on- target and VEGF off-target site 1 amplified from 600 ng genomic DNA to increase detection sensitivity to 1/198,000.
• Nuclease type wt Cas9 wt Cas9 nickase fCas9 wt Cas9 nickase fCas9 gRNA pair target: CLTA CLTA CLTA CLTA GFP GFP GFP GFP
• Nuclease type wt Cas9 wt Cas9 nickase fCas9 wt Cas9 nickase fCas9 gRNA pair: EMX EMX EMX GFP GFP GFP Total expression
• Nuclease type wt Cas9 wt Cas9 nickase fCas9 wt Cas9 nickase fCas9 gRNA pair: VEGF VEGF VEGF GFP GFP GFP GFP Total expression
• Nuclease type nickase fCas9 nickase fCas9
• gRNA pair VEGF VEGF GFP GFP
• nickases enable double- stranded breaks to be specified by two distinct gRNA
• fCas9 modified target DNA sites with efficiency comparable to that of nickases, and with > 140- fold higher specificity than wild-type Cas9.
• Target sites that conform to the substrate requirements of fCas9 are abundant in the human genome, occurring on average once every 34 bp.
• Cas9:gRNA-induced double strand breaks can result in functional gene knockout through non-homologous end joining (NHEJ) or alteration of a target locus to virtually any sequence through homology-directed repair (HDR) with an exogenous DNA template.
• NHEJ non-homologous end joining
• HDR homology-directed repair
• 9 ' 15 ' 16 Cas9 is an especially convenient genome editing platform, as a genome editing agent for each new target site of interest can be accessed by simply generating the corresponding gRNA. This approach has been widely used to create targeted knockouts and gene insertions in cells and model organisms, and has also been recognized for its potential therapeutic relevance.
• studies 1 5 have reported the ability of Cas9 to cleave off- target genomic sites, resulting in modification of unintended loci that can limit the usefulness and safety of Cas9 as a research tool and as a potential therapeutic. It was hypothesized that engineering Cas9 variants to cleave DNA only when two simultaneous, adjacent Cas9:DNA binding events take place could substantially improve genome editing specificity since the likelihood of two adjacent off-target binding events is much smaller than the likelihood of a single off-target binding event (approximately l/n vs. l/n). Such an approach is distinct from the recent development of mutant Cas9 proteins that cleave only a single strand of dsDNA, such as nickases.
• nickases can be used to nick opposite strands of two nearby target sites, generating what is effectively a double strand break, and paired Cas9 nickases can effect substantial on-target DNA modification with reduced off-target modification. 5 ' 6 ' 8 Because each of the component Cas9 nickases remains catalytically active 9 11 and single- stranded DNA cleavage events are weakly mutagenic, 18 ' 19 nickases can induce genomic modification even when acting as monomers. 5 ' 7 ' 16 Indeed, Cas9 nickases have been previously reported to induce off-target modifications in cells.
• an obligate dimeric Cas9 system is provided herein.
• fusing the Fokl restriction endonuclease cleavage domain to a catalytically dead Cas9 (dCas9) created an obligate dimeric Cas9 that would cleave DNA only when two distinct i3 ⁇ 4M-dCas9:gRNA complexes bind to adjacent sites ("half- sites") with particular spacing constraints (Figure 6D).
• the length of the linker sequence was varied as either one or three repeats of Gly-Gly-Ser (GGS) between the Fokl and dCas9 domains. Since previously developed dimeric nuclease systems are sensitive to the length of the spacer sequence between half-sites, 23 ' 24 a wide range of spacer sequence lengths was tested between two gRNA binding sites within a test target gene, Emerald GFP (referred to hereafter as GFP) ( Figure 6C and Figure 9). Two sets of gRNA binding-site pairs with different orientations were chosen within GFP. One set placed the pair of NGG PAM sequences distal from the spacer sequence, with the 5' end of the gRNA adjacent to the spacer (orientation A) ( Figure 6C), while the other placed the PAM sequences immediately adjacent to the spacer
• orientation B Figure 9
• seven pairs of gRNAs were suitable for orientation A, and nine were suitable for orientation B.
• eight spacer lengths were tested in both dimer orientations, ranging from 5 to 43 bp in orientation A, and 4 to 42 bp in orientation B.
• DNA constructs corresponding to 104 pairs of i3 ⁇ 4M-dCas9:gRNA complexes were generated and tested, exploring four fusion architectures, 17 protein linker variants (described below), both gRNA orientations and 13 spacer lengths between half- sites.
• Cas9 protein variants and gRNA were generated in cells by transient co-transfection of the corresponding Cas9 protein expression plasmids together with the appropriate pair of gRNA expression plasmids.
• the i3 ⁇ 4M-dCas9 variants, nickases, and wild-type Cas9 all targeted identical DNA sites using identical gRNAs.
• the XTEN protein was originally designed to extend the serum half-life of translationally fused biologic drugs by increasing their hydrodynamic radius, acting as protein-based functional analog to chemical PEGylation. 35 Possessing a chemically stable, non-cationic, and non-hydrophobic primary sequence, and an extended conformation, it is hypothesized that a portion of XTEN could function as a stable, inert linker sequence for fusion proteins.
• the sequence of the XTEN protein tag from E-XTEN was analyzed, and repeating motifs within the amino acid sequence were aligned.
• FokI-dCas9 fusion construct FokI-L8 ( Figure 12A) was derived from the consensus sequence of a common E-XTEN motif, and a 16 amino acid sequence was chosen from within this motif to test as a FokI-dCas9 linker.
• NLS-GGS-i3 ⁇ 4M-XTEN-dCas9 construct consistently exhibited the highest activity among the tested candidates, inducing loss of GFP in -15% of cells, compared to -20% and -30% for Cas9 nickases and wild-type Cas9 nuclease, respectively ( Figure 7A). All subsequent experiments were performed using this construct, hereafter referred to as fCas9.
• the T7 endonuclease I Surveyor assay 28 was used to measure the amount of mutation at each of seven target sites within the integrated GFP gene in HEK293 cells treated with fCas9, Cas9 nickase, or wild-type Cas9 and either two distinct gRNAs in orientation A or no gRNAs as a negative control.
• fCas9 was able to modify the GFP target sites with optimal spacer lengths of -15 or -25 bp at a rate of -20%, comparable to the efficiency of nickase-induced modification and approximately two-thirds that of wild- type Cas9 (Figure 7A-C).
• fCas9 can modify genomic DNA efficiently and in a manner that requires simultaneous engagement of two guide RNAs targeting adjacent sites, unlike the ability of wild-type Cas9 and Cas9 nickase to cleave DNA when bound to a single guide RNA.
• column 2 shows the number of sites in the human genome with paired gRNA binding sites in orientation A allowing for a spacer length from -8 bp to 25 bp (column 1) between the two gRNA binding sites.
• gRNA binding sites in orientation A have the NGG PAM sequences distal from the spacer sequence (CCNN 2 o- spacer- N 20 NGG).
• Column 3 shows the number of sites in the human genome with paired gRNA binding sites in orientation B allowing for a spacer length from 4 to 25 bp (column 1) between the two gRNA binding sites.
• gRNA binding sites in orientation B have the NGG PAM sequences adjacent to the spacer sequence (N 2 oNGG spacer CCNN 2 o) .
• NC indicates the number of sites in the human genome was not calculated.
• Negative spacer lengths refer to target gRNA binding sites that overlap by the indicated number of base pairs.
• Table 4 (B) shows the sum of the number of paired gRNA binding sites in orientation A with spacer lengths of 13 to 19 bp, or 22 to 29 bp, the spacer preference of fCas9 ( Figure 16).
• Cas9 off-target sites of CLTA, EMX, and VEGF genomic target sites were measured. 1 ' 2 ' 6 ' 8
• the target site and its corresponding known off-target sites were amplified from genomic DNA isolated from HEK293 cells treated with fCas9, Cas9 nickase, or wild-type Cas9 and two gRNAs spaced 19 bp apart targeting the CLTA site, two gRNAs spaced 23 bp apart targeting the EMX site, two gRNAs spaced 14 bp apart targeting the VEGF site, or two gRNAs targeting an unrelated site (GFP) as a negative control.
• In total 11 off-target sites were analyzed by high-throughput sequencing.
• the sensitivity of the high-throughput sequencing method for detecting genomic off-target cleavage is limited by the amount genomic DNA (gDNA) input into the PCR amplification of each genomic target site.
• gDNA genomic DNA
• a 1 ng sample of human gDNA represents only -330 unique genomes, and thus only -330 unique copies of each genomic site are present.
• PCR amplification for each genomic target was performed on a total of 150 ng of input gDNA, which provides amplicons derived from at most 50,000 unique gDNA copies. Therefore, the high-throughput sequencing assay cannot detect rare genome modification events that occur at a frequency of less than 1 in 50,000, or 0.002%.
• VEG_Off 1 (SEQ ID NO: 196)
• VEG_Off2 (SEQ ID NO: 197)
• VEG_Off3 (SEQ ID NO: 198)
• VEG_Off4 (SEQ ID NO: 199) GCAGATGTAGTGTTTCCACAGGG
• fCas9 exhibited a greater on- target:off-target DNA modification ratio than that of Cas9 nickase (> 5,150 and 1,650 for fCas9, versus 510 and 1,230 for Cas9 nickase, Figure 8G).
• VEGF off-target site 1 On either side of VEGF off-target site 1 there exist no other sites with six or fewer mutations from either of the two half-sites of the VEGF on-target sequence.
• the first 11 bases of one gRNA (V2) might hybridize to the single-stranded DNA freed by canonical Cas9:gRNA binding within VEGF off-target site 1 ( Figure 18C).
• gRNA DNA hybridization it is possible that a second Cas9 nickase or fCas9 could be recruited to modify this off-target site at a very low, but detectable level.
• Judicious gRNA pair design could eliminate this potential mode of off-target DNA cleavage, as VEGF off-target site 1 is highly unusual in its ability to form 11 consecutive potential base pairs with the second gRNA of a pair.
• fCas9 was unable to modify the genomic off-target sites tested because of the absence of any adjacent second binding site required to dimerize and activate the Fokl nuclease domain.
• the observed low off-target: on-target modification ratios of fCas9 likely arises from the distinct mode of action of dimeric Fokl, in which DNA cleavage proceeds only if two DNA sites are occupied simultaneously by two Fokl domains at a specified distance (here, -15 bp or -25 bp apart) and in a specific half-site orientation.
• the resulting unusually low off-target activity of fCas9 enable applications of Cas9:gRNA-based technologies that require a very high degree of target specificity, such as ex vivo or in vivo therapeutic modification of human cells.
• site-specific nucleases also have potential as gene therapy agents, and site-specific zinc finger endonucleases have recently entered clinical trials: CCR5-2246, targeting a human CCR-5 allele as part of an anti-HIV therapeutic approach.
• inventive Cas9 variants of the present disclosure may be used to inactivate CCR5, for example in autologous T cells obtained from a subject which, once modified by a Cas9 variant, are re-introduced into the subject for the treatment or prevention of HIV infection.
• the CCR5 gene is targeted in T cells obtained from a subject.
• T cells are one of the white blood cells used by the body to fight HIV.
• Cas9 variants e.g., fCas9
• gRNA capable of inactivating CCR5 are then delivered to the isolated T cells using a viral vector, e.g., an adenoviral vector.
• a viral vector e.g., an adenoviral vector.
• suitable Cas9 variants includelde those inventive fusion proteins provided herein.
• suitable target sequences for gRNAs targetting the CCR5 allele include those described in Figure 19, e.g., SEQ ID NOs:303-310 and 312-317.
• the viral vector(s) capable of expressing the Cas9 variant and gRNA is/are added to the isolated T cells to knock out the CCR5 protein.
• T cells When the T cells are returned to subject, there is minimal adenovirus or Cas9 variant protein present.
• the cells are then reintroduced to the subject for the treatment or prevention of HIV/AIDS.
• MDKKYSIGLAIGTNSVGWAVITDEYKVPSKKFKVLGNTDRHSIKKNLIGALLFDSGE TAEATRLKRTARRRYTRRKNRICYLQEIFSNEMAKVDDSFFHRLEESFLVEEDKKHE RHPIFGNIVDEVAYHEKYPTIYHLRKKLVDSTDKADLRLIYLALAHMIKFRGHFLIEG DLNPDNSDVDKLFIQLVQTYNQLFEENPINASGVDAKAILSARLSKSRRLENLIAQLP GEKKNGLFGNLIALSLGLTPNFKSNFDLAEDAKLQLSKDTYDDDLDNLLAQIGDQYA DLFLAAKNLSDAILLSDILRVNTEITKAPLSASMIKRYDEHHQDLTLLKALVRQQLPE

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