Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07H—SUGARS; DERIVATIVES THEREOF; NUCLEOSIDES; NUCLEOTIDES; NUCLEIC ACIDS
  • C07H21/00—Compounds containing two or more mononucleotide units having separate phosphate or polyphosphate groups linked by saccharide radicals of nucleoside groups, e.g. nucleic acids
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07K—PEPTIDES
  • C07K1/00—General methods for the preparation of peptides, i.e. processes for the organic chemical preparation of peptides or proteins of any length
  • C07K1/04—General methods for the preparation of peptides, i.e. processes for the organic chemical preparation of peptides or proteins of any length on carriers
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
  • 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
  • C12N15/10—Processes for the isolation, preparation or purification of DNA or RNA
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
  • C12P19/00—Preparation of compounds containing saccharide radicals
  • C12P19/04—Polysaccharides, i.e. compounds containing more than five saccharide radicals attached to each other by glycosidic bonds

Definitions

• the present invention concerns the construction of biopolymers through assembly of shorter biopolymer sequences, for example, assembly of genes from oligonucleotides, polypeptides from oligopeptides, and polysaccharides from oligosaccharides.
• the present invention also relates to the remodeling, or reconstruction of biopolymers, wherein a section of the biopolymer sequence is excised, then replaced by a modified segment.
• DNA is the chemical substance that makes up the genomes of most life forms.
• Two properties of DNA that are fundamental to its in vivo function and to the ability of scientists to manipulate it in vitr are that (i) DNA is composed of four different subunits ("bases"), adenine (A), guanine (G), cytosine (C) and thymine (T) , linked together by a sugar-phosphate backbone to form long polymeric strands, and (ii) two "complementary" strands of DNA come together to form a double helical DNA molecule by specific hydrogen bonded base pairing (A pairs with T and G pairs with C) .
• bases adenine
• G guanine
• C cytosine
• T thymine
• This specific base pairing plays an important role in chromosomal replication, a process in which the two DNA strands of a chromosome become separated, then a DNA polymerase enzyme uses each strand as a "template” to synthesize a complementary strand which then base pairs with the template strand, thereby resulting in the formation of two chromosomes from one.
• RNA poly erase enzyme utilizes the base pairing properties of one strand of a gene to synthesize a "messenger RNA" molecule (a nucleic acid in which uracil replaces thymine and the sugar is ribose instead of 2"-deoxyribose) .
• the messenger RNA is subsequently "translated” into protein as directed by the genetic code (each 3-base '"codon" in the messenger RNA specifies a certain amino acid to be incorporated into a protein product).
• the coupled transcription/translation process results in biosynthesis of a protein molecule that contains an amino acid sequence that is encoded by the base sequence in the DNA.
• the amino acid sequence in the protein determines how the protein folds into a specific structure and how it interacts with other molecules in its biochemical function, for example, catalysis of a specific chemical reaction in the case of an enzyme.
• base pairing forms the basis of the "annealing" reaction that is employed in a variety of laboratory DNA manipulations: Two separated DNA strands will spontaneously pair up to form a duplex structure throughout the region(s) of complementarity if, and only if, they contain one or more stretches of complementary base sequence.
• solid phase supports for chemical synthesis of DNA contributed most importantly to the ability to rapidly and efficiently synthesize DNA chemically, because the growing chain is covalently attached to an insoluble support, permitting reagents to be washed away between chemical steps, thus eliminating the need to purify the polynucleotide product after each addition of monomer.
• solid phase synthesis permits automation of the process, so that each base addition (via multistep reaction cycle) can be carried out in about ten minutes at room temperature (Smith, American Biotechnology Laboratory (Dec, 1983); Caruthers, Science, 23 . 0:281-285 (1955)).
• SUBSTITUTE SH ⁇ X synthesis has been hindered by: (i) the high cost of synthesis of all the oligonucleotides needed to assemble an average gene (typically $5,000 to $20,000); and (ii) the slow and labor intensive nature of gene assembly from synthetic oligonucleotides.
• Chemical synthesis of DNA currently produces polynucleotides up to 100-150 bases in length (and at the upper limits the yield is very low) .
• the coding portion of the average gene however, consists of 1000-base pairs.
• duplex DNA which contains strand interruptions at alternating positions along the two strands, is then converted to a contiguous duplex segment, by enzymatic ligation. Only then can the duplex DNA be cloned into a vector for subsequent analysis and expression (protein production) .
• Restriction endonucleases enzymes that recognize and cleave DNA at specific sequences, 4-8 base pairs in length
• DNA ligases enzymes which join together fragments of DNA resulting from action of restriction enzymes
• plasmids or viral DNAs extrachromosomal replicating genomes
• h i biopolymers from subcomponenents thereof.
• Another object of the present invention is to provide a process for more rapid assembly of genes or gene segments by stepwise annealing of synthetic oligonucleotides.
• Yet another object of the present invention is to provide a more cost effective process for assembly of genes or gene segments by stepwise annealing of synthetic oligonucleotides requiring less labor and materials.
• a further object of the present invention is to provide a more efficient process for assembly of genes or gene segments by stepwise annealing of synthetic oligonucleotides requiring fewer purification and analytical steps.
• Still another object of the present invention is to provide a more efficient process for assembly of genes or gene segments by stepwise annealing of synthetic oligonucleotides, providing a greater yield of the desired end-product .
• An additional object of the present invention is to provide a faster, more efficient and less costly process for assembly of peptides into polypeptides.
• a further object of the present invention is to provide an improved process for replacement of a specific segment of a DNA molecule by an analogous, modified segment or by a different segment.
• Yet another object of the present invention is to provide an improved process for replacement of a specific segment of a polypeptide molecule by an analogous, modified segment or by a new, unrelated segment.
• Still another object of the present invention is to provide an improved process for deletion of one or more specific segments within a nucleic acid or protein.
• An additional object of the present invention is to provide an improved process for insertion of one or more oligomeric segments at specific locations in a nucleic acid or protein.
• an improved, general procedure for construction of biopolymers comprising the following steps: (1) attachment of a biopolymer subcomponent to a solid phase support; (2) attachment of the next biopolymer sequence to one end of the support-bound component; (3) washing away of excess, unattached biopolymer sequences added in step (2); (4) ordered, stepwise attachment of oligomeric biopolymer sequences to the free end of the support-bound component (by repeated conduct of steps (2) and (3)), resulting in assembly of the biopolymer; and (5) release on the assembled biopolymer from the support.
• All steps in the foregoing process can be carried out in a suspension of the support, or alternatively, in a packed bed column fitted with porous means at both ends to provide a flow-through system.
• the biopolymer to be constructed by this process is chosen from among the group consisting of DNA (genes or gene segments) , polypeptides (proteins), polysaccharides, or any other biopolymer composed of subsections that can be joined together.
• the "starting" biopolymer component initially attached to the support can range widely in length, for example 1-100 residues, the precise length being a matter of choice, but the support-bound starting component will typically be 10-50 residues in length.
• the nature of the solid phase support is a matter of choice, provided that the structure of the support does not sterically hinder the assembly of the desired high molecular weight biopolymer.
• the linkage of "starting" biopolymer component to the solid phase support is a matter of choice, readily achievable by one skilled in the art, using a variety of prior art methods.
• the nature of the stepwise linkage of oligomeric biopolymer segments during the assembly process, as well as the method of cleavage of final product from the support, will depend on the type of biopolymer being
• an improved process for assembly of a gene (or gene fragment) from synthetic oligonucleotides comprising the following steps: (1) attachment of a "starting" oligonucleotide to the solid phase support, at or near one of its two ends; (2) addition of a molar excess of the next oligonucleotide in the gene to be assembled, one end of the added oligonucleotide being complementary in base sequence to the free end of the support-bound oligomer, to form a molecule in which one end of the added oligonucleotide is base paired with the support-bound oligomer, leaving a single-stranded tail at the other end of the added oligomer; (3) washing away of the unannealed free oligonucleotides;, (4) repeated cycles of oligonucleotide addition/annealing/washing, carried out until the desired gene or gene fragment has been assembled; and (5) release of the assembled
• the solid phase support is first derivatized with a nucleoside, then the "starting" oligonucleotide is synthesized on the solid phase support, using standard phosphate triester or phosphite triester procedures, the linkage of this synthesized oligonucleotide to the support being retained and utilized in the subsequent gene assembly.
• the solid phase support in this embodiment is preferably nonporous glass beads of small diameter (5-50 micrometers) or small diameter (5-50 micrometers) glass beads containing large diameter (1000-5000 A) pores. Derivatization of the glass beads with nucleoside can be achieved by a variety of prior art methods that are readily apparent to one skilled in the art. For example, the 3"-urethane linkage of a nucleoside to the glass via long chain alkylamine spacer arm (Sproat and Brown, Nucl.
• SUBSTITUTES ⁇ E Acids Res. , 11:2979-2987, (1985) can be employed to yield a solid phase support suitable for synthesis of the "starting" oligonucleotide by standard phosphoramidite or phosphate triester methods.
• the urethane linkage is largely retained during the deprotection of exocyclic amino groups, and can subsequently be utilized for solid phase gene assembly.
• solid phase synthesis of the "starting" oligonucleotide can proceed via the phosphoramidite method or phosphate triester method on glass beads derivatized with nucleoside via the standard 3"-0-succinyl linkage, provided that the sequence of the "starting" oligonucleotide is chosen to avoid nucleoside residues containing exocyclic amino groups, since the alkaline condition normally required for deprotection of exocyclic amino groups would cleave the DNA from the support.
• a starting oligonucleotide sequence consisting of thymidine and inosine residues would be appropriate.
• step (1) of another preferred embodiment attachment of the "starting" oligonucleotide to the solid phase support
• a preformed oligonucleotide is bonded to the support at or near one end.
• the nature of the solid phase support and the method of linkage between support and "starting" oligonucleotide are a matter of choice, readily acheivable by one skilled in the art, using procedures known in the art with the qualification that the structure of the solid phase must not sterically hinder the assembly of the gene and the linkage of the oligonucleotide to the support must withstand the conditions of stepwise annealing, used for subsequent gene assembly.
• the solid phase support for this embodiment of step (1) appropriately comprises nonporous latex microspheres derivatized by functional groups, such that chemical crosslinking or condensation can occur between the beads and a reactive group on one end of the starting oligonucleotide in the assembly.
• oligonucleotide to the latex particles can be achieved by a variety of established procedures which would be apparent to one skilled in the art.
• hydrazide-derivatized latex particles are readily linked to oligonucleotides derivatized at the 5'-end with aldehyde or carboxylic acid groups as described by Kremsky et al., Nucleic Acids Res.. 15:2891 -2909, (1 987)).
• alkylamine-derivatized beads may be linked to alkylamine-derivatized oligonucleotides, using a bifunctional crosslinking reagent such as disuccinimedyl suberate as described by Pilch & Czech, J. Biol. Chem. 254:3375-3381 (1979).
• alkylamine-derivatized latex particles can first be linked to avidin or streptavidin by glutaraldehyde activation such as described by Goodfried et al., Science 144:1344 (1964), then the first oligonucleotide in the assembly, labeled with biotin at its 5*-end, will attach to the beads through the well known tight avidin-biotin affinity.
• Step (2) in the gene assembly process may be carried out under any of the standard annealing conditions known to those skilled in the art, for example, incubation at 50-65° C in the presence of 0.2-1 M NaCl or KCI, or incubation at 37° C in the presence of 0.2-1 M salt plus 50% formamide.
• the base sequence of the oligonucleotides may be chosen to satisfy the following specifications: (1) The desired base sequence of gene is generated by the assembly process; (2)
• the extent of complementary overlap may be any length so long as to provide the required stability of the association is provided.
• the complementary overlap sequence will be at least about 10 bases and may be up to 50 bases;
• the length of protruding single-stranded "tail" after annealing is preferably at least 10 bases (the length yielding stable base pairing with the subsequently added oligonucleotide);
• Oligonucleotide sequences are preferably chosen to avoid secondary structure within the oligonucleotides (intrastrand base pairing resulting in hairpins), which may interfere with annealing of the added oligonucleotide to the support-bound component; and
• the sequences are chosen to avoid the production of more than one annealing product (through a multiplicity of base pairing possibilities) .
• Step (3) in the gene assembly can conveniently be achieved by flow of solvent past the solid phase support, for example through a reaction chamber containing porous members at both ends.
• step (3) can be accomplished by a series of brief centrifugation/ decanting steps in microcentrifuge tubes.
• the oligonucleotides assembled are designed to yield a completely duplex DNA with strand interruptions at positions alternating along both strands.
• the oligonucleotides are designed for assembly of a partially duplex DNA molecule, in which single-stranded gaps exist in alternating positions along both strands. These gaps may be filled in by action of a DNA polymerase in vitro.
• Step (4) may also be carried out by addition of several (eg., about 2-5) oligonucleotides in each annealing step. Although this procedure potentially reduces the total number of annealing steps required for assembly of the desired gene or gene fragment, care must be taken to insure that multiple products of annealing are not generated, i.e., that all support-bound assemblies generate the identical, desired duplex DNA sequence.
• Step (5) (release of the assembled gene from the support) is carried out by means chosen to be compatible with the nature of the linkage of DNA to the support and the structure of the assembled DNA.
• the stepwise annealing is carried out with all oligonucleotides being 5 '-phosphorylated except for one, such that a completely duplex DNA is formed in which all strand interruptions can be sealed by use of DNA ligase, except for a single nonligatable strand interruption adjacent to the support-linked oligonucleotide.
• the contiguous duplex segment may then be removed from the support by brief heating to 80-100° C.
• the nonligatable strand interruption adjacent to the support can be made by leaving a gap of one or more nucleoside residues at this position in the assembled DNA.
• step 5 of another preferred embodiment appropriate oligonucleotides are selected for the assembly such that a duplex DNA segment containing a restriction enzyme recognition sequence is generated between the gene or gene fragment and the support, such that release of the DNA from the support can be conveniently achieved via cleavage by the restriction endonuclease.
• the DNA released from the support is conveniently cloned into a vector for expression in cells and DNA sequence analysis.
• the solid phase support comprises small diameter (5-50 micrometers) nonporous glass beads to which the first amino acid residue is covalently attached via a long chain alkylamine spacer arm.
• the solid phase support comprises small diameter (5-50 micrometers) glass beads containing pores of large diameter (1000-5000 A) . Both supports serve to avoid steric hindrance during the assembly of long polypeptides.
• the peptide can be attached to the supports after the synthesis of the peptide, or alternatively, the glass beads can be first derivatized with an amino acid residue, then used for solid phase peptide synthesis to create a support-bound peptide which is subsequently elongated in the assembly process.
• the preceding embodiments give examples of the kind of solid phase support and the type of linkage of peptide to the support which may be utilized, these parameters are a matter of choice.
• One skilled in the art could devise alternate peptide-linked supports that possess the favorable steric properties suitable for polypeptide assembly.
• Peptide-linked nonporous latex microspheres may also be used as a solid phase support.
• step (2) of one preferred embodiment of the solid phase polypeptide assembly (stepwise block condensation) of the present invention the stepwise condensation of amino terminus-protected peptides onto the free amino terminus of a peptide linked to the support via its carboxy terminus, is carried out using the standard Fmoc procedure.
• stepwise block condensation on the solid phase support is performed
• SUBSTITUTESHEET chemically, by use of a peptide bond-forming reagent such as dichlorophenol, or enzymatically, by "reverse proteolysis” (Offord, Protein Engineering. 1:151-157, (1987)) .
• a general procedure for remodeling of biopolymer sequences on a solid phase support comprising the following steps: (1) attachment of a high molecular weight biopolymer at one or more positions in the biopolymer sequence to a solid phase support; (2) excision of a specific segment of the biopolymer; (3) washing away of the cleaving agents and excised biopolymer segment; (4) addition of a chemically synthesized biopolymer sequence or a fragment isolated from natural sources and specific insertion of the added segment into the biopolymer sequence to replace the excised segment; (5) washing away of excess added biopolymer segment and bond-reforming agents;, and (6) cleavage of remodeled biopolymer from the support.
• the foregoing general procedure for biopolymer remodeling can also be used to insert or delete biopolymer segments at specific positions in the biopolymer sequence.
• step (1) of biopolymer remodeling the nature of the solid phase support and means for its attachment to the support are a matter of choice, depending on the structure of biopolymer, and would be readily chosen from existing applications by one skilled in the art.
• avidin-coated beads could be used to tightly bind biotin-labeled DNA or biotin-labeled protein.
• a specific antibody-bound support could be used to bind an epitope in a protein or nucleic acid.
• a support-linked oligonucleotide (preferably 20-50 residues in length) could be used to link a single-stranded DNA molecule to the support, via hydrogen bonded base pairing.
• a reversible crosslinking agent could be used to connect chemically reactive groups in the biopolymer and support.
• (2) of solid phase biopolymer remodeling is preferably achieved by enzymatic means, utilizing one or more restriction endonucleases in the case of DNA, or specific endopeptidases in the case of protein.
• cleavage by restriction endonuclease can be achieved by adding oligonucleotides which anneal to the DNA to provide short duplex regions containing the enzyme"s recognition sequence.
• a specific chemical cleavage means for example, cleavage of protein by cyanogen bromide
• step (2) can also be employed in step (2) .
• step (3) of solid phase biopolymer remodeling the cleaving agents and excised biopolymer segment are ashed from the support, preferably by flow of solvent past the support-bound biopolymer contained within a chamber fitted with porous means at both ends.
• step (3) repeated brief centrifugation/decantation steps can be used in step (3) for support-bound biopolymer contained within microcentrifuge tubes.
• step (4) of solid phase biopolymer remodeling a "replacement" biopolymer segment is added, preferably in molar excess over support-bound biopolymer, along with an appropriate bond-reforming agent, to achieve replacement of the biopolymer segment excised in step (2) by the segment added in step (4) .
• a "replacement" biopolymer segment is added, preferably in molar excess over support-bound biopolymer, along with an appropriate bond-reforming agent, to achieve replacement of the biopolymer segment excised in step (2) by the segment added in step (4) .
• DNA a restriction fragment isolated from natural sources or a chemically synthesized duplex segment containing the appropriate termini may be added, and ligated into the position previously occupied by the segment excised in step (2), by the action of DNA ligase.
• DNA ligase a restriction fragment isolated from natural sources or a chemically synthesized duplex segment containing the appropriate termini
• replacement of the excised segment by an added peptide can be achieved enzymatically, by "reverse proteolysis” catalyzed by specific endopeptidases under reaction conditions such as disclosed in Offord, Protein 5 Engineering. 1:151-157, (1987)), or can be achieved
• Suborn ⁇ cSn : chemically, by action of a peptide bond-forming agent such as dichlorophenol.
• step (5) Washing away of excess reaction components from the support-bound biopolymer (step (5)) may be achieved by the same means is in step (3).
• Cleavage of the remodeled biopolymer from the support can be carried out by a variety of means that would be apparent to one skilled in the art, the method of choice depending on the nature of the solid phase support and biopolymer and the type of linkage between them.
• the linkage is readily broken by addition of buffer containing 100 M dithiothreitol Shimkus et al., Proc Natl. Acad. Sci.
• dissociation of remodeled biopolymer from an antibody affinity support can be achieved by common protein denaturants, and release of a DNA molecule base paired to a support-bound oligonucleotide can be achieved by brief heating to 80-100° C.
• Figure 1 is a schematic diagram of the solid phase biopolymer assembly process as applied to construction of a gene or gene fragment.
• Figure 2 is a schematic diagram of the solid phase biopolymer assembly process as applied to construction of a polypeptide.
• Figure 3 is a schematic diagram of the general procedure for remodeling of a biopolymer on a solid phase support.
• Figure 1 illustrates the concept of assembly of a gene or gene fragment on a solid phase support.
• a "starting"' oligonucleotide 3 is first attached to a solid phase support 1.
• the precise nature of the support 1 and the type of linkage 2 between the starting oligonucleotide and the support are a matter of choice, and are readily known to those of skill in the art. It is essential, however, that the geometry of the solid phase support is such that assembly of the gene is not sterically hindered, as it would be with most currently used solid phase support materials.
• a solid phase support consisting of small diameter (5-50 micrometers) nonporous glass beads, or alternatively, macroporous beads (5-50 micrometers in diameter) with very large pores (1000-5000 A) are recommended for use in solid phase assembly of genes.
• linkage 2 of the starting oligonucleotide to the beads can take a variety of forms, readily known to those of skill in the art.
• the following examples of suitable linkages are given for illustrative purposes, and it is emphasized that alternative linkages, readily apparent to one skilled in the art, are also within the scope of the present invention.
• linkage 2 to glass beads is the urethane linkage described by Sproat and Brown supra and incorporated herein by reference.
• the urethane linkage is ideally suited for a synthesis of a starting oligonucleotide of any base sequence prior to gene
• the starting oligonucleotide in gene assembly is designed to contain a sequence of I (inosine) and T (thymidine) nucleosides, then the standard 3"-0-succinyl linkage can be used to synthesize the starting oligonucleotide, because an alkaline base-deblocking step (which would hydrolyze the 3 '-0-succinyl linkage) would not be required after synthesis of oligo(I,T).
• oligonucleotide Several procedures are available for linkage of a presynthesized starting oligonucleotide to the surface of solid latex microspheres, providing a support-bound oligonucleotide suitable for gene assembly.
• the well-known tight avidin-biotin affinity may be employed, by covalently linking avidin to small alkylamine-derivatized latex beads (0.1-10 microns in diameter) by the glutaraldehyde activation or other methods known in the art, producing avidin-coated beads that will bind a 5 '-biotin-labeled oligonucleotide.
• Latex microspheres may also be covalently attached to the starting oligonucleotide for gene assembly by other methods, including the use of a homobifunctional crosslinking agent such as disuccinimedyl suberate to link alkylamine-derivatized latex beads with 5"-alkylamine-derivatized oligonucleotide, linkage of hydrazide-derivatized latex beads to a 5"-aldehyde-oligonucleotide or to a
• a homobifunctional crosslinking agent such as disuccinimedyl suberate to link alkylamine-derivatized latex beads with 5"-alkylamine-derivatized oligonucleotide
• linkage of hydrazide-derivatized latex beads to a 5"-aldehyde-oligonucleotide or to a
• SUBSTITUTE SHEET stepwise annealings, using oligonucleotides 4, 5, 6, 7, and n to build up the desired gene or gene fragment.
• the degree of base "Overlap" at each annealing step will preferably result in formation of at least twenty base pairs between added oligonucleotide and support-bound single-stranded "tail.”
• the starting oligonucleotide is attached to the support via its 3"-end, and is non-phosphorylated.
• Oligonucleotides added in the stepwise annealing reactions are 5"-phosphorylated and designed to form a fully double-stranded assembled DNA (containing no single-stranded "gaps"), in which the strand interruptions (5*-phosphate adjacent to 3'-OH) in one strand are located at approximately the midpoint of the oligonucleotides comprising the other strand. Under these conditions, the '"nicks'" can be enzymatically sealed by action of DNA ligase, prior to release of the assembled gene from the support.
• the stepwise annealing in gene assembly is preferably carried out in a small volume (eg., 0.02-0.10 ml) , with the solid phase support kept in suspension by gentle agitation (except with submicron latex particles, which are kept in suspension by Brownian motion) .
• the quantity of starting oligonucleotide attached to the support can vary widely, for example, 0.01-1.0 micromoles per gram of beads.
• essentially quantitative stepwise annealing would occur within a few minutes under the following reaction conditions (0.10 ml annealing volume): 50 mM potassium or sodium phosphate, pH 7.5, 400 mM KCl or NaCl, 0.
• T TE HE micrograms per ml The quantity of each added oligonucleotide in the gene assembly is very low, accommodating the use of inexpensive methods of oligonucleotide synthesis that provide low yields of purified product.
• annealing of one oligonucleotide at a time is recommended, to insure that annealing occurs specifically and quantitatively.
• the procedure illustrated in Fig. 1 could be successfully adapted to the addition of several oligonucleotides at a time, thereby requiring fewer steps to assemble a gene.
• a 1000 base pair gene could be assembled within six hours, assuming assembly of fifty 40mers, five minute annealing time and two minute washing time.
• the washing step carried out after each annealing reaction is preferably carried out by flow of solvent (eg., annealing buffer) past the support, which may be provided for by housing the solid phase support within a reaction chamber having porous means at both ends such as that disclosed in U.S. Patent application Serial No. 000,716.
• solvent eg., annealing buffer
• 2-3 brief centrifugation/ decantation steps may be carried out (with support held within a microcentrifuge tube) to achieve satisfactory washing.
• oligonucleotides added at each step be homogeneous.
• the DNA product After the completion of the gene assembly the DNA product must be released from the support. In the example shown in Fig. 1, this is simply achieved by a brief heating step (80-90° C) , which denatures the short duplex section holding the assembled gene to the support, without
• SUBSTITUTE SHEET causing complete denaturation of the long assembled duplex DNA (the latter having been converted to contiguous long strands by action of DNA ligase) .
• the unsealed strand interruption at the beginning of the assembled gene (at the junction of oligonucleotides 3 and 5 in Fig. 1, resulting from the absence of a 5'-phosphate on the support-bound starting oligonucleotide) could also be arranged by formation of a nonligatable "gap" of at least one base at this position.
• the assembled gene or gene fragment could conveniently be released from the support by action of a restriction endonuclease, provided that its recognition sequence were designed into the duplex DNA near the support (eg., within the duplex segment formed by oligonucleotide 4 in Fig. 1).
• a restriction endonuclease provided that its recognition sequence were designed into the duplex DNA near the support (eg., within the duplex segment formed by oligonucleotide 4 in Fig. 1).
• 5'-phosphorylation of the oligonucleotides used to assemble the gene may be optional.
• the released gene (or gene fragment) 9 may be used for any purpose, i.e., it may be subsequently cloned into a vector for sequence analysis, expression (production of protein encoded by the gene), etc.
• the base sequence of the oligonucleotides to be assembled should be carefully planned, with the following considerations in mind: (1) The sequences should be designed to avoid formation of hairpins of four or more base pairs within the oligonucleotides, which may interfere with efficient intermolecular base pairing during the annealing steps. (2) Sequences that are commonly associated with poor coupling efficiency during the chemical synthesis (such as four or more consecutive G residues) should be avoided. (3) Sequences that introduce "rare codons" into a gene should be avoided, if possible, if the aim is to achieve high levels of gene expression.
• Random codons are those nucleotide sequences which are rarely found in nature and thus may not be properly translated in some hosts.
• Oligonucleotides may be designed to generate unique restriction sites within the assembled gene to facilitate subsequent manipulations by recombinant DNA techniques. For example, if mutations are found at intervals within a chemically synthesized gene, the existence of unique restriction sites permits cleavage of individual cloned genes with restriction endonucleases, and recombination to form the desired mutant-free gene.
• the length of a duplex DNA that may be assembled in the manner illustrated in Fig. 1 ranges widely, from less than a hundred base pairs up to thousands of base pairs. Because labor-intensive purification and analysis of intermediates in the gene assembly are avoided by use of the solid phase approach, time and expense associated with gene construction are greatly reduced by use of the present invention. Furthermore, the high efficiency of the process permits the use of very small quantities of DNA, further reducing the cost of gene synthesis.
• An average size gene may be synthesized, assembled and cloned into an expression vector within a period of one week, at a total cost for materials and labor of less than $1,000 if the segmented DNA synthesis device disclosed and claimed in U.S. Patent Application No. 000,716, filed Jan. 6, 1987 is used to synthesize the oligonucleotides at 50 nanomole scale, and then the present invention were used to assemble the gene.
• the cost of preparing the same gene by conventional methods would be $20,000 to $50,000 and would typically require about two months work.
• the present invention although exemplified as a means for gene assembly, is equally applicable to construction of other biopolymers, including polypeptides and polysaccharides.
• the method of the present invention used for polypeptide assembly is shown in Figure 2.
• a protein molecule could be constructed by ordered, stepwise
• the present invention may also be applied to remodeling of a biopolymer, a multistep process which, if carried out in solution by conventional means, frequently requires time-consuming and labor-intensive purification and analytical steps before the desired end product is obtained.
• a biopolymer reconstruction on a solid phase support is illustrated in Figure 3.
• Biopolymer 11 is first attached to a solid phase support 1 at one or more positions in the biopolymer sequence.
• a solid phase support 1 As explained previously for the process of biopolymer assembly, the precise nature of the solid phase support and the method of linkage of biopolymer thereto are entirely a matter of choice, the only constraint being that the structure of the solid phase support must not restrict accessibility of reaction components to the biopolymer. Suitable solid phase supports, types of linkages, means for washing away reaction components and means for ultimate release of biopolymers from the supports such as those described previously for biopolymer assembly may be utilized.
• the support-bound biopolymer 11 (for example, a double-stranded plasmid DNA) is treated with at least one agent (for example, restriction endonuclease(s)) to produce cleavage at one or more specific sites 13 within the biopolymer sequence. If the biopolymer is cleaved at two specific sites, one or more specific fragment(s) 12 were released (for example, a restriction fragment) .
• at least one agent for example, restriction endonuclease(s)
• E released fragment(s) 12 and cleaving agent(s) are conveniently washed away, as described previously for biopolymer assembly, then a replacement fragment 14 (for example, a restriction fragment or synthetic duplex DNA) is added, and the bonds are reformed (for example, by DNA ligase), producing the remodeled biopolymer 15.
• a replacement fragment 14 for example, a restriction fragment or synthetic duplex DNA
• This procedure may be used to produce a deletion within the biopolymer, by reforming the bonds after removal of the released segment 12, without adding back a replacement segment.
• this procedure may be used to insert an additional biopolymer segment into a specific location within the support-bound biopolymer, by cleaving at a single site within the biopolymer, and then attaching a biopolymer segment at this position (for example, insertion of a "'foreign'" duplex segment or synthetic duplex DNA at a unique restriction site within a cloning vector, to produce a recombinant DNA) .
• the application of the present invention to recombinant DNA technology is advantageous, because of the elimination of time-consuming purification steps that are typically carried out in order to remove a released DNA segment before replacing it with another sequence.
• a specific application of the present invention for manipulation of single-stranded circular DNA (such as a bacteriophage M13 vector) is now given, with reference to Fig. 3.
• a circular, single-stranded phage DNA 11 is conveniently attached to the solid phase support via base pairing with a support-bound synthetic oligonucleotide (20-50 bases in length, complementary to a specific region within the single-stranded vector).
• a support-bound synthetic oligonucleotide (20-50 bases in length, complementary to a specific region within the single-stranded vector).
• two synthetic oligonucleotides eg., 20mers
• Restriction endonuclease(s) are then used to cleave out a segment 12 of the DNA between the restriction sites, and the restriction enzyme(s) and released fragment are washed away. Then a replacement fragment 14 (containing short duplex regions at the ends, with identical termini as in the fragment removed) is added and joined to the support-bound DNA by action of DNA ligase.
• a restriction fragment or synthetic DNA will be inserted at this position.
• the DNA can be made completely double-stranded by action of a DNA polymerase, and as polymerization proceeds through the short duplex region connecting the vector to the support-bound oligonucleotide, the vector is released from the former, by the well-known "'strand displacement” phenomenon. Finally, the DNA may be converted to closed circular form by action of DNA ligase.
• EXAMPLE 2 Synthesis and assembly of a segment of the E. coli lacl gene.
• Solid Phase Support The support used for both synthesis of the
• a support was derivatized by the method described by Sproat and Brown with 0.1 umoles of a first nucleoside (A) .
• a non-phosphorylated oligonucleotide (3'-AAAAAAAAAAAAAAAAAAGCGTCGCACGCT-5' ) was synthesized on the support by the phosphoramidite method (Beaucage & Caruthers, 1981), using a Milligen 7500 DNA synthesizer.
• the support material was placed into a glass vial and treated with 1.5 ml concentrated ammonium hydroxide at 55° C. for 1 hour to remove the protecting groups from the exocyclic amino groups.
• the support material was then placed into a 1.5 ml Eppendorf tube and washed five times (by centrifugation/decantation) with annealing buffer (as specified below) .
• oligonucleotide-support (approx. 1 nmole) , 2 nanomole of the 5 '-phosphorylated oligonucleotide,
• annealing buffer 50 mM kH PO.,pH 7.5, 400 mM KCl, ImM EDTA
• the tube was incubated at 55° C. for 5 minutes, with occasional gentle agitation, then the tube was centriguged for 1 minute in an Eppendorf microcentrifuge and the beads were washed twice with 1 ml annealing buffer.
• the support was washed twice with ligase buffer (50 mM Trisl-HCl, pH 7.8, 20mM dithiothreitol, lO M MgCl 2 , ImM ATP, 0.05 mg/ml bovine serum albumin), then resuspended in 0.098 ml ligase buffer. Two microliters of DNA ligase was added (New England Biolabs, high specific activity grade) . After incubation for 30 minutes at 37° C.
• ligase buffer 50 mM Trisl-HCl, pH 7.8, 20mM dithiothreitol, lO M MgCl 2 , ImM ATP, 0.05 mg/ml bovine serum albumin
• the support was then washed twice with Ava 1 buffer (lOmM Tris-HCl, pH 8, 50mM NaCl, lOmM MgCl_, 5mM 2-mercaptoethanol, 0.1 mg/ml bovine serum albumin), then resuspended in 0.098 ml of this buffer.
• Ava 1 buffer lOmM Tris-HCl, pH 8, 50mM NaCl, lOmM MgCl_, 5mM 2-mercaptoethanol, 0.1 mg/ml bovine serum albumin
• the beads were washed twice with 0.1 ml Ava 1 buffer, and the DNA in the combined supernatants were ethanol precipitated and dissolved in 0.1 ml of lOmM Tris-HCl, pH 7.5 containing ImM EDTA.
• SUBSTITU iE SH ⁇ coli strain PD8 This genetic system provides the opportunity to assess the possible generation of mutations during the chemical synthesis of the lacl gene fragment (mutations are seen as blue plaques in the absence of inducer) . The frequency of mutations in this experiment was undetectable over the spontaneous frequency.
• the DNA of the semi-synthetic M13-lacl was sequenced by the "dideoxy" method and found to contain the desired wild-type sequence in the region of the chemical synthesis.
• the DNA duplex synthesized by the method of the present invention was identical in both sequence and mutation frequency to that of the naturally occurring wild-type lacl sequence.
• Fig. 2 illustrates a general procedure for biopolymer reconstruction (remodeling)
• many variations of the process specific for different bipolymers and different types of manipulations thereupon, will be evident to one skilled in the art and are within the scope of the present invention.
• the solid phase remodeling process could be used to replace a specific segment of a protein with a different, modified segment, a solid phase "recombinant protein" technique analogous to the solid phase recombinant DNA example discussed previously.
• a solid phase "recombinant protein" technique analogous to the solid phase recombinant DNA example discussed previously.

Applications Claiming Priority (2)

Publications (2)

Family

ID=22820059

Family Applications (1)

Country Status (4)

Families Citing this family (85)

Citations (1)

• 1989
  • 1989-07-03 JP JP50757189A patent/JPH03505966A/ja active Pending
  • 1989-07-03 EP EP19890908080 patent/EP0427745A4/en not_active Withdrawn
  • 1989-07-03 WO PCT/US1989/002915 patent/WO1990000626A1/en not_active Application Discontinuation
  • 1989-07-03 AU AU38692/89A patent/AU3869289A/en not_active Abandoned

Patent Citations (1)

Non-Patent Citations (2)

Also Published As

Similar Documents

Legal Events