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  • A61P35/00—Antineoplastic agents
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P35/00—Antineoplastic agents
  • A61P35/02—Antineoplastic agents specific for leukemia
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
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  • C12N2310/00—Structure or type of the nucleic acid
  • C12N2310/10—Type of nucleic acid
  • C12N2310/11—Antisense
  • C12N2310/111—Antisense spanning the whole gene, or a large part of it

Definitions

• Ubiquitin-proteasome pathway constitutes a major system used by cells to control signaling networks.
• proteins are marked with a chain of ubiquitin molecules, which are linked to the target and to each other through isopeptide linkages with lysine residues (Pickart et al. (2004) Biochim. Biophys. Acta. 1695:55; Pickart (2004) Cell 116:181).
• Ubiquitin is a 76 amino acid protein which becomes linked to lysine residues through its C-terminal glycine residue.
• Defects in the UPP can also contribute to neurodegenerative diseases, such as Parkinson's Disease and the like. While ubiquitination plays a critical role in targeted protein degradation, it also plays important roles in controlling protein localization, the function of membrane proteins, endocytosis and other processes.
• Protein ubiquitination is known to involve three major protein activities (Hershko et al. (1983) J. Biol. Chem. 258:8206; Ganoth et al. (1988) J. Biol. Chem. 263:12412).
• ubiquitin is activated to form a high-energy thiol ester bond with an El ubiquitin activating enzyme.
• This process initially involves formation of an ubiquitin adenylate with the C-terminal glycine of ubiquitin (G76), consuming one molecule of ATP, followed by transfer of the G76 carboxylate to the active site cysteine to form a thiol ester (Haas et al. (1982) J.
• the El-Ub thiol ester complex binds an E2 ubiquitin conjugating enzyme through the Els C-terminal E2 -binding domain. Ubiquitin is then transferred from the active site cysteine in El to the active site cysteine in the E2 (Pickart et al. (1985) J. Biol. Chem. 260:1573.
• the E2 ⁇ Ub complex then dissociates from the El where it can interact with E3 ubiquitin ligases to promote transfer of ubiquitin to lysine residues either in the substrate or on growing poly-ubiquitin chains (Eletr et al. (2005) Nat. Struct. MoI. Biol. 12:933).
• the El enzyme plays a critical role in the ubiquitination process by allowing ubiquitin activation and facilitating ubiquitin transfer.
• UPP components As drug targets for disease. Indeed, the first drug targeting the UPP, VELCADE ® (Millennium Pharmaceuticals, Inc., Cambridge, MA), was approved by the FDA in 2003 (Popat et al. (2006) Expert Opin. Pharmacother. 7:1337). VELCADE ® targets the 26S proteasome, thereby blocking degradation of all proteins whose turnover requires the proteasome. VELCADE ® has proven useful for the treatment of multiple myeloma. Id. Its mode of action appears to rely on the enhanced sensitivity of certain types of cancer cells for proteasome activity, possibly reflecting an increased requirement for the NFKB pathway, which relies on the proteasome. However, proteasome inhibition is also potentially toxic to normal cells and therefore, obtaining new drug targets with increased specificity would be useful. SUMMARY
• the present invention is based in part on the surprising discovery of a novel ubiquitin activating enzyme, Uba6.
• Uba6 a novel ubiquitin activating enzyme
• This discovery is particularly unexpected given the longstanding dogma in the field that a single activating enzyme exists for ubiquitin.
• the enzymatic properties of Uba6 differ substantially from the classical ubiquitin activating enzyme Ubel, indicating that Uba6 plays biological roles that are distinct from Ubel.
• Uba6 employs ATP in its catalytic mechanism, small molecule inhibitors that selectively inhibit the activity of Uba6 could be useful in controlling signaling pathways that depend specifically upon the activity of Uba6 in organisms such as humans.
• methods for inhibiting a Uba6 activity are provided.
• inhibition is achieved by contacting Uba6 with a compound that inhibits formation of a ubiquitin-adenylate intermediate (e.g., the compound binds an adenylation domain of Uba6), contacting Uba6 with a compound that inhibits thiol esterification of Uba6, or contacting Uba6 with a compound that inhibits transfer of ubiquitin to a ubiquitin conjugating enzyme (e.g., the compound binds a UbI domain of Uba6).
• a compound that inhibits formation of a ubiquitin-adenylate intermediate e.g., the compound binds an adenylation domain of Uba6
• a compound that inhibits thiol esterification of Uba6 e.g., the compound binds transfer of ubiquitin to a ubiquitin conjugating enzyme
• inhibition is performed in vitro (e.g., using cell extracts) or in vivo (e.g., in a tissue culture cell or in an organism).
• the ubiquitin conjugating enzyme is one or more of E2C, E2D1, E2D2, E2D3, E2D4, E2E1, E2G, E2S, E2T and E2Z (also referred to herein as Usel).
• a method for inhibiting ubiquitin activation including contacting Uba6 with a compound that inhibits a catalytic cysteine domain of Uba6 is provided.
• inhibition is performed in vitro (e.g., cell extracts) or in vivo (e.g., in a tissue culture cell or in an organism).
• a method of reducing a Uba6 activity in an organism in need thereof including administering to the organism one or more siRNAs complementary to a portion of a Uba6 mRNA.
• the siRNA is an RNA sequence including one or more of SEQ ID NO:1, SEQ ID NO:2 and SEQ ID NO:3.
• the portion of the Uba6 mRNA encodes a ThiF domain, a catalytic cysteine domain, an adenylate domain or a ubiquitin-like domain.
• the organism is a human.
• a method of reducing ubiquitination in an organism in need thereof including administering to the organism one or more compounds that inhibits one or more Uba6 activities in the organism.
• the compound is an antibody or an siRNA.
• the organism is a human.
• a method of identifying a compound that inhibits charging of E2Z including providing a sample including E2Z and ubiquitin, contacting the sample with the compound, contacting the sample with Uba6 or a biologically active portion thereof, and determining whether the ubiquitin is bound to the E2Z in the presence of the compound, wherein the ubiquitin is not bound to the E2Z if the compound inhibits charging of E2Z is provided.
• the method further includes visualizing E2Z on an SDS-PAGE gel.
• a method of identifying a compound that inhibits a Uba6 activity including providing a sample including a ubiquitin conjugating enzyme and ubiquitin, contacting the sample with the compound, contacting the sample with Uba6 or a biologically active portion thereof, and determining whether the ubiquitin is bound to the ubiquitin conjugating enzyme in the presence of the compound, wherein the ubiquitin is not bound to the ubiquitin conjugating enzyme if the compound inhibits the Uba6 activity is provided.
• the ubiquitin conjugating enzyme is selected from the group consisting of: E2C, E2D1, E2D2, E2D3, E2D4, E2E1, E2G, E2S, E2T and E2Z.
• a method of identifying a compound that inhibits a Uba6 activity including providing a sample including ubiquitin, contacting the sample with the compound, contacting the sample with Uba6 or a biologically active portion thereof, and determining whether the ubiquitin is bound to the Uba6 or the biologically active portion thereof in the presence of the compound, wherein the ubiquitin is not bound to the Uba6 if the compound inhibits the Uba6 activity is provided.
• the ubiquitin is bound to the Uba6 or the biologically active portion thereof via thiol conjugation.
• the ubiquitin is immobilized.
• an RNA sequence having at least about 70% identity to a nucleic acid sequence selected from the group consisting of SEQ ID NO:1, SEQ ID NO:2 and SEQ ID NO:3, wherein the RNA sequence can inhibit a Uba6 activity is provided.
• the Uba6 activity is selected from one or more of ubiquitin activation, ubiquitin-adenylate intermediate formation, ubiquitin thiol esterification, ubiquitin transfer to a ubiquitin-conjugating enzyme and/or ubiquitination of a target polypeptide.
• the RNA is siRNA.
• an RNA sequence selected from the group consisting of SEQ ID NO:1, SEQ ID NO:2 and SEQ ID NO:3 is provided.
• the RNA sequence can inhibit a Uba6 activity such as ubiquitin activation, ubiquitin-adenylate intermediate formation, ubiquitin thiol esterification, ubiquitin transfer to a ubiquitin- conjugating enzyme and/or ubiquitination of a target polypeptide.
• the RNA is siRNA.
• FIGS IA-I H depict physical and functional characteristics of Uba6.
• A Phylogenetic tree for ThiF-domain containing proteins in humans, zebrafish (D. rerio) and sea urchin (S. purpuratus). Also included are mouse Ubelx and Ubely proteins as well as S. cerevisiae Ubalp. The sequences and tree were generated using ClustalW.
• B SDS-PAGE analysis of Flag-tagged Uba6 (Uba6 F ) expressed and purified from insect cells (Coomassie staining).
• C, D Uba6 functions as an activating enzyme for ubiquitin but not for several ubiquitin- like proteins (Ulps).
• the indicated GST-Ulps were purified after expression in bacteria and mixed with purified Uba6 F in the presence of ATP. After 10 minutes at 30 0 C, reaction mixtures were subjected to SDS-PAGE under non-reducing conditions prior to visualization using Coomassie blue. In lane 4, Uba6 F is converted to a Uba6 F ⁇ GST-Ub conjugate. In panel D, various components were omitted to demonstrate a requirement for GST-Ub and ATP and to demonstrate that the conjugate is sensitive to the reducing agent DTT. *, GST breakdown products. (E) The related El enzyme UbelL promotes activation of ISG 15 but not ubiquitin.
• GST-UbelL purified from insect cells was assayed for activation of GST-ISG15 and GST-Ub. While it was active toward ISG 15, as expected, it failed to activate GST-Ub, even though it is more closely related to Ubel phylogenetically than is Uba6.
• GST-MPl was used as a negative control.
• F Kinetics of ubiquitin activation by Ubel and Uba6 were performed as described further herein. Error bars indicate standard deviation of duplicate assays.
• G Association of Uba6 with ubiquitin-agarose. El capture on ubiquitin-Agarose using 293T/Flag-HA-Uba6 extracts (pH 7.5).
• Extracts from 293T cells stably expressing HA-Flag-Uba6 were subjected to the classical ubiquitin affinity chromatography experiments of Hershko ⁇ infra). Extracts were incubated with ubiquitin-agarose in the presence of ATP to allow for ubiquitin charging. Beads were then washed with buffer containing Triton X-IOO followed by elution with DTT. Load, flow-thru, washes, eluate and proteins remaining bound to ubiquitin-agarose were then subjected to immunob lotting with anti-Ubel and anti-HA antibodies to detect HA-Flag-Uba6. (H) Conservation of Uba6 in vertebrates.
• Uba6 and Ubel from human (Hs), mouse (Mm), S. cerevisiae (Sc) and zebrafish (Danio rerio, Dr). Zebrafish sequences were provided under accession number XP 695755.2. Unlike humans, the mouse contains two closely related (90% identical) Ubel proteins, Ubelx located on the X-chromosome and Ubely located on the Y-chromosome. The Ubely protein is thought to be involved in spermatogenesis (Levy et al. (2000) Mamm. Genome 11 :164; Mitchell et al. (1992) Nature 359:528). Dark green, adenylate domain; light green, ThiF motifs; red, catalytic cysteine domain (CCD); blue, ubiquitin-fold domain (Ufd).
• Figures 2A-2D depict data showing that Uba6 is charged with ubiquitin in vivo.
• A 293T cells stably expressing Flag-HA-Uba6, Flag-HA-Uba6 C625A , or Flag-HA- Uba6 C625S using a lentiviral vector under control of the CMV promoter were lysed in extraction buffer and subjected to immunoprecipitation with anti-HA antibodies. Immune complexes were separated by SDS-PAGE under non-reducing conditions and either immunob lotted with anti-HA, anti-Nedd8, or anti-ubiquitin, or alternatively, the blot was stained with Ponceau S to reveal proteins.
• Extracts from cells expressing Flag-HA-Uba6C625S were subjected to purification using anti-Flag and anti-HA resins and the proteins separated by SDS-PAGE. Individual bands were subjected to mass spectrometry. The slower mobility band contained three peptides from ubiquitin, while the faster mobility form lacked associated ubiquitin-derived peptides.
• D Depletion of Uba6 using RNAi. siRNAs targeting GFP (as a control) or Uba6 were transfected into 293 T cells using OLIGOFECT AMINETM (Invitrogen, Carlsbad, CA). After 72 hours, cells were lysed and extracts subjected to immunob lotting using anti-Uba ⁇ antibodies.
• siRNA sequences used for Uba ⁇ were: #1 : CCUUGGAAGAGAAGCCUGAUGUAAA (SEQ ID NO:1); #2: ACACUGAAGUUAUUGUACCGCAUUU (SEQ ID NO:2); #3: GGGAUCGAUGGACCGUACAUGGAAA (SEQ ID NO:3).
• Purified Flag-Ha-Uba6 was used as a positive control for the immunoblot.
• FIGS 3A-3C depict data showing that Uba ⁇ and Ubel display distinct preferences for charging of E2 ubiquitin conjugating enzymes.
• the indicated E2s were produced using a bacterial in vitro translation system and metabolically labeled with 35 S-methionine. E2s were mixed with Flag-HA-Uba6 or Flag-HA-Ubel (expressed and purified from insect cells) and incubated at 30 0 C for 30 minutes. Reaction mixtures were subjected to non-reducing SDS-PAGE and proteins visualized by autoradiography. An aliquot of E2 was included as a control for charging.
• B Summary of E2 charging data.
• FIG. 4A-4C depict data showing that E2 specificity of Uba6 resides in its C- terminal UbI domain.
• A Domain structures of Ubel and Uba6 showing the percent conservation over the catalytic domains and the C-terminal Ubiquitin-like (UbI) domain.
• B Conservation of the C-terminal UbI domains from Ubel and Uba6. Alignment was generated using ClustalW.
• C Chimeric proteins in which the UbI domains of Uba6 and Ubel were swapped with each other were created.
• Cdc34 is charged by Ubel but not Uba6 (lanes 2 and 3). Both Els lacking the UbI domain were inactive, while Uba6 containing the UbI domain of Ubel was active for Cdc34 charging.
• Figure 5 depicts the cDNA sequence encoding Homo sapiens Uba6 (SEQ ID NO:4) (GenBank Accession Number NM_018227).
• Figure 6 depicts the amino acid sequence of Homo sapiens Uba6 (SEQ ID NO:5) (GenPept Accession Number NP 060697).
• Figure 7 depicts the cDNA sequence encoding Mus musculus Uba6 (SEQ ID NO:6) (Gen Bank Accession Number NM_172712).
• Figure 8 depicts the amino acid sequence of Mus musculus Uba6 (SEQ ID NO:7) (GenPept Accession Number NP 766300).
• Figure 9 depicts the cDNA sequence encoding E2Z from Homo sapiens (SEQ ID NO: 8) (Gen Bank Accession Number NM_023079.2).
• Figure 10 depicts the amino acid sequence encoding E2Z from Homo sapiens (SEQ ID NO:9) (GenPept Accession Number NP_075567.1 has the partial sequence).
• FIG. 1 IA-I ID depict data showing that the C-terminal domains of Ubel and Uba6 control E2 specificity.
• A Domain structures of Uba6 and Ubel and a schematic showing how the C-terminal UbI domains were interchanged to form the chimeric proteins.
• B Model of the domain structure of an El enzyme based on the crystal structure of the Nedd8 activating enzyme.
• C E2 charging assays were performed using the indicated El proteins and E2 conjugating enzymes.
• D Predicted structures of the UbI domains of Ubel and Uba6.
• FIG. 12 depicts data showing that Uba6 is required to charge E2Z in vivo.
• Left panel formation of the E2Z ⁇ ubiquitin thiolester required the active site cysteine of E2Z (C>A mutant) and was reduced by addition of DTT.
• Right panel Depletion of Uba6, but not Ubel, by RNAi blocked charging of E2Z in vivo.
• the indicated siRNAs were transfected into 293 T cells stably expressing Flag-HA-E2Z. Extracts were generated in MES buffer (pH 4.5) and proteins immediately separated by SDS- PAGE. After transfer to nitrocellulose, blots were probed with the indicated antibodies.
• FIG. 13 A-E depict Uba6 activation of ubiquitin in vivo.
• A El expression in cultured cells. Anti-Uba6 and anti-Ubel were used to probe blots of extracts from the indicated cell lines, with recombinant Flag-Ela as controls.
• B Lysates (pH 7.5) from 293T/Flag-HA-Uba6 cells (wild-type, C625S or C625A; 20 ⁇ g) or anti-HA immune complexes from 0.2 mg of extract were separated on 4-12% Tris-glycine reducing gels and immunoblotted with anti-Uba ⁇ , anti-HA or anti-ubiquitin.
• E Mass spectral analysis of ubiquitin-activated Uba6. The Flag-HA-Uba6 C625S protein used is described further herein.
• FIGS 14A-14D depict the systematic analysis of E2 conjugating enzymes for targets of Uba6.
• A E2 charging activity of ubiquitin Els depicted on a phylogenetic tree of active E2s.
• B Uba6 and Ubel display distinct E2 charging activities in vitro. Assays employed 35 S-methionine labeled E2s made in E. coli S30 extracts, KO ubiquitin, and the indicated El, as described in METHODS. *, non-specific translation products.
• C Sequence conservation of human Ubel and Uba6.
• D Charging of Cdc34B, UbcH5D, and Usel (also referred to herein as E2Z) in vitro by chimeric El proteins was examined using 35 S-methionine labeled E2s.
• FIGS 15A-15D depict the distinct requirements for charging of the ubiquitin conjugating enzymes Usel and Cdc34 in vivo.
• A Scheme depicting the mechanism of E2 charging in cells. E2s exist as a mixture of charged and uncharged forms, depending upon how rapidly the charged form is generated and used.
• B HeLa cells were transfected with the indicated siRNAs. After 72 hours, cells were lysed at pH 4.5, proteins separated on a non-reducing 4-12% Bis-Tris gradient gel and immunob lotted.
• C Usel is charged in mammalian cells through its catalytic cysteine.
• FIGS 16A-16C depict structural information of Els.
• A Structural organization of Els. Ubel, UbeLl and Uba6 are single chain Els while Uba3/APP-BPl and Uba2/Sael are heterodimeric Els.
• B Predicted structure of Ufd domains from Uba6 and Ubel, and a comparison with the Ufd domain from Uba3. Predicted structures were generated using "Modeller" software (release 8v2) with the SUMO El Sae2 as template (PDB code 1Y8Q) and displayed using Pymol.
• Uf(P *1 residues 948-1058.
• Uf(P *6 residues 949-1052.
• Uf(P *3 residues 349-440.
• C Domain specific sequence identities among human Uba6, Ubel and UbelL. Percent identities and percent similarities are shown.
• Figure 17 depicts that Uba6 and Usel are widely expressed in human cell lines and tissues. Expression of Ubel is shown for comparison. Expression patterns were obtained using the Genomics Institute of the Novartis Research Foundation transcriptional profiling resource (Su et al. (2002) Proc. Natl. Acad. Sci. U.S.A. 99:4465; Su et al. (2004) Proc. Natl. Acad. Sci. U.S.A. 101 :6062).
• FIG. 1 Figures UA-UF depict the analysis of GST-UBL proteins.
• UbelL activates ISG 15 but not ubiquitin.
• Reaction mixtures were subjected to 4- 12% Tris-glycine and proteins visualized with Coomassie Blue.
• GST-UbelL, GST- Ubel, and GST-MPl were expressed in insect cells and purified as described previously (Zhao et al. (2004) Proc. Natl Acad. Sci. U.S.A.
• Flag-Uba6 (8 nM) was incubated with varying concentrations of GST-Ub or GST-Nedd8 (0, 5, 10, 20, 40, 80 ng) in the presence of 2 mM ATP and reaction mixtures subjected to 4-12% Tris-glycine and immunob lotting using anti- Flag antibodies. Uba6 activated GST-Ub but not GST-Nedd8. (D) GST-ubiquitin titration. Eight nM Uba6 or Ubel was incubated with the indicated concentration of GST-ubiquitin for 10 min at 30 ° C. Samples were subjected to electrophoresis on a 4- 12% Tris-glycine non-reducing gel prior to immunob lotting with the indicated antibody.
• FIGS 19A-19B depict that Uba6 activates ubiquitin but not Nedd8 in vivo and in vitro.
• A Tandem mass spectra for a ubiquitin-derived peptide co-migrating with the slow-mobility form of Flag-HA-Uba6 C625S isolated from 293T cells. The spectra of the TLSDYNIQK peptide from ubiquitin is shown.
• B Flag-HA-Uba6 was isolated from extracts (10 mg) derived from the indicated cell lines lysed in pH 7.5 buffer and proteins separated by non-reducing 4-12% Tris-glycine followed by staining with Coomassie Blue. Upper and lower bands were subjected to mass spectrometer. The ubiquitin peptides identified are shown and the relevant statistics for these peptides were collected as described further herein.
• Figures 20A-20G depict sequence alignments of Use 1 proteins from vertebrates and analysis of E2 charging.
• A Phylogenetic tree of the human E2 ubiquitin conjugating enzyme family, including the non-catalytic sub-class typified by Uev. The accession numbers for individual E2 family members used to generate the tree are provided. E2 sequences were aligned in ClustalW and the tree displayed in Treeview.
• B Alignments were generated in Clustal W. Sequences for frog (Xenopus) and zebrafish (Danio rerio) Usel were obtained by blast analysis of the EST database using human Usel as the query.
• FIGS 21A-21E depict structural modeling of Uba6 ufd -Usel and Ubel ufd -Cdc34 interfaces.
• A Model-based sequence alignments of human Uba6, Ubel, and Uba3 as well as alignments for the Hl helices of Cdc34A, Usel, and Ubcl2. Residues located at the interface are shown in red. Identical residues are shaded in black. Similar residues are shaded in grey.
• Figure 22 depicts the sequences of genes examined as described further herein.
• Ubel is the sole activating enzyme for ubiquitin encoded by the genomes of all eukaryotes. This conclusion is based on the presence of a single essential ubiquitin El in budding yeast and the finding that rodent tissue culture cells containing temperature sensitive mutations in Ubel display cell cycle arrest phenotypes consistent with there being only a single gene (Finley et al. (1984) Cell 37:43; Ciechanover et al. (1984) J. Cell. Biochem. 24:27). As described further herein, it has surprisingly been discovered that this dogma is incorrect, and vertebrate organisms contain two distinct activating enzymes for ubiquitin.
• this novel enzyme promotes the conjugation of ubiquitin to ubiquitin conjugating enzymes (e.g., E2s) in a manner that appears to be distinct from Ubel. Accordingly, Uba6 can have specific functions in the ubiquitin pathway and, therefore, is an important drug target.
• ubiquitin conjugating enzymes e.g., E2s
• the ubiquitin-proteasome pathway plays a central role in the turnover of many key regulatory proteins involved in transcription, cell cycle progression and apoptosis, all of which are important in disease states. See, e.g., King et al. (1996) Science 274:1652; Vorhees et al. (2003) Clin. Cancer Res. 9:6316; Adams et al. (2004) Nat. Rev. Cancer 4:349. Accordingly, targeting ubiquitin-activating enzymes provides a unique opportunity to interfere with a variety of biochemical pathways important for maintaining the integrity of cell division and cell signaling. Ubiquitin-activating enzymes, such as Uba6, function at the first step of ubiquitin conjugation pathways.
• Uba6 enzyme should specifically modulate the downstream biological consequences of a ubiquitin modification.
• inhibition of these activating enzymes, and the resultant inhibition of downstream effects of ubiquitin- conjugation represents a method of interfering with the integrity of cell division, cell signaling, and several aspects of cellular physiology which are important for disease mechanisms.
• ubiquitin-activating enzymes such as Uba6, as regulators of diverse cellular functions, are potentially important therapeutic targets for the identification of novel approaches to treatment of a variety of diseases and disorders (i.e., "ubiquitin-related disorders").
• the Uba6 and/or E2Z (also referred to herein as Usel) modulating agents described herein can be used in the treatment of cellular proliferative disorders, e.g., cancer.
• the role of the UPP pathway in oncogenesis has led to the investigation of proteasome inhibition as a potential anticancer therapy.
• modulation of the UPP pathway by inhibition of the 26S proteasome by VELCADE® has proven to be an effective treatment in certain cancers and is approved for the treatment of relapsed and refractory multiple myeloma.
• proteins whose levels are controlled by the UPP pathway include the CDK inhibitor p27 Kipl and the inhibitor of NFKB, IKB. See, Podust et al. (2000) Proc. Natl. Acad. ScL USA 97:4579; Read et al. (2000) MoI. Cell Biol. 20:2326. Inhibition of the degradation of p27 can block the progression of cells through the Gl and S phases of the cell cycle. Interfering with the degradation of IKB can prevent the nuclear localization of NF- ⁇ B, transcription of various NF- ⁇ B-dependent genes associated with the malignant phenotype, and resistance to standard cytotoxic therapies.
• NF -KB plays a key role in the expression of a number of pro-inflammatory mediators, implicating a role for such inhibitors in inflammatory disorders. Accordingly, inhibition of UPP is useful for the treatment of inflammatory disorders, including, e.g., rheumatoid arthritis, asthma, multiple sclerosis, psoriasis, reperfusion injury and the like.
• Inhibition of UPP is also useful for treatment of disorders such as neurodegenerative disorders, including e.g., Parkinson's disease, Alzheimer's disease, triplet repeat disorders; neuropathic pain; ischemic disorders, e.g., stroke, infarction, kidney disorders; and cachexia.
• neurodegenerative disorders including e.g., Parkinson's disease, Alzheimer's disease, triplet repeat disorders; neuropathic pain; ischemic disorders, e.g., stroke, infarction, kidney disorders; and cachexia.
• cellular proliferative disorders includes disorders characterized by undesirable or inappropriate proliferation of one or more subset(s) of cells in a multicellular organism.
• cancer refers to various types of malignant neoplasms, most of which can invade surrounding tissues, and may metastasize to different sites (see, for example, PDR Medical Dictionary 1st edition (1995)).
• neoplasm and tumor refer to an abnormal tissue that grows by cellular proliferation more rapidly than normal and continues to grow after the stimuli that initiated proliferation is removed (see, for example, PDR Medical Dictionary 1st edition (1995)). Such abnormal tissue shows partial or complete lack of structural organization and functional coordination with the normal tissue which may be either benign (i.e., benign tumor) or malignant (i.e., malignant tumor).
• treatment of cellular proliferative disorders is intended to include the prevention of the growth of neoplasms in a subject or a reduction in the growth of preexisting cancers in a subject.
• the inhibition also can be the inhibition of the metastasis of a cancer from one site to another.
• the cancer is a solid tumor.
• solid tumors that can be treated by the methods of the invention include pancreatic cancer; bladder cancer; colorectal cancer; breast cancer, including metastatic breast cancer; prostate cancer, including androgen-dependent and androgen-independent prostate cancer; renal cancer, including, e.g., metastatic renal cell carcinoma; hepatocellular cancer; lung cancer, including, e.g., non-small cell lung cancer (NSCLC), bronchioloalveolar carcinoma (BAC), and adenocarcinoma of the lung; ovarian cancer, including, e.g., progressive epithelial or primary peritoneal cancer; cervical cancer; gastric cancer; esophageal cancer; head and neck cancer, including, e.g., squamous cell carcinoma of the head and neck; melanoma; neuroendocrine cancer, including metastatic neuroendocrine tumors; brain tumors, including, e.g., glioma, an
• the cancer is a hematologic malignancy.
• hematologic malignancy include acute myeloid leukemia (AML); chronic myelogenous leukemia (CML), including accelerated CML and CML blast phase (CML-BP); acute lymphoblastic leukemia (ALL); chronic lymphocytic leukemia (CLL); Hodgkin's disease (HD); non-Hodgkin's lymphoma (NHL), including follicular lymphoma and mantle cell lymphoma; B-cell lymphoma; T-cell lymphoma; multiple myeloma (MM); Waldenstrom's macroglobulinemia; myelodysplastic syndromes (MDS), including refractory anemia (RA), refractory anemia with ringed siderblasts (RARS), (refractory anemia with excess blasts (RAEB), and RAEB in transformation (RAEB-T); myeloprolifer
• AML acute myeloid leukemia
• Cellular proliferative disorders can further include disorders associated with hyperproliferation of vascular smooth muscle cells such as proliferative cardiovascular disorders, e.g., atherosclerosis and restinosis.
• Cellular proliferation disorders can also include disorders such as proliferative skin disorders, e.g., X-linked ichthyosis, psoriasis, atopic dermatitis, allergic contact dermatitis, epidermolytic hyperkeratosis, and seborrheic dermatitis.
• Cellular proliferative disorders can further include disorders such as autosomal dominant polycystic kidney disease (ADPKD), mastocystosis, and cellular proliferation disorders caused by infectious agents such as viruses.
• ADPKD autosomal dominant polycystic kidney disease
• mastocystosis cellular proliferation disorders caused by infectious agents such as viruses.
• Compounds of the present invention include inhibitors of one or more ubiquitin- activating enzyme activities.
• the compounds are designed to be inhibitors of one or more Uba6 activities (e.g., ubiquitin activation; ubiquitin- adenylate intermediate formation; ubiquitin thiol esterification; ubiquitin transfer to one or more ubiquitin-conjugating enzymes (e.g., E2s); and/or ubiquitination of one or more target polypeptides (e.g., ubiquitin, an E2, a target polypeptide and/or protein or the like)) and/or one or more E2Z activities (e.g., ubiquitin activation; ubiquitin- adenylate intermediate formation; ubiquitin thiol esterification; ubiquitin transfer to one or more ubiquitin-protein ligases (e.g., E3s); and/or ubiquitination of one or more target polypeptides
• Inhibitors include, but are not limited to, compounds which modulate (e.g., reduce) the promoting effects of El enzymes in ubiquitin conjugation to target proteins (e.g., reduction of ubiquitin activation and/or facilitating ubiquitin transfer to E2). Inhibitors also include, but are not limited to, compounds which modulate (e.g., reduce) the promoting effects of E2Z enzymes in ubiquitin conjugation to target proteins (e.g., reduction of ubiquitin activation and/or facilitating ubiquitin transfer to E3).
• the compounds of this invention may be assayed for their ability to inhibit a Uba6 enzyme and/or an E2Z enzyme in vitro or in vivo (e.g., in cells or animal models) according to methods provided in further detail herein, or methods known in the art.
• the compounds may be assessed for their ability to bind or mediate a Uba6 enzyme and/or an E2Z enzyme activity directly.
• the activity of compounds may be assessed through indirect cellular assays, or assays of downstream effects of Uba6 and/or E2Z activation to assess inhibition of downstream effects of Uba6 inhibition.
• activity may be assessed by detection of ubiquitin- conjugated substrates (e.g., ubiquitin-conjugated E2s, ubiquitin-conjugated E3s, ubiquitinated substrates and the like); detection of downstream protein substrate stabilization; detection of inhibition of UPP activity; and the like.
• ubiquitin- conjugated substrates e.g., ubiquitin-conjugated E2s, ubiquitin-conjugated E3s, ubiquitinated substrates and the like.
• Assays for assessing activities are described further herein and/or are known in the art.
• One embodiment of this invention relates to a composition
• a composition comprising a compound described herein or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.
• the compounds of this invention may be derivatized at functional groups to provide prodrug derivatives which are capable of conversion back to the parent compounds in vivo.
• prodrugs include the physiologically acceptable and metabolically labile ester derivatives, such as methoxymethyl esters, methylthiomethyl esters, or pivaloyloxymethyl esters derived from a hydroxyl group of the compound or a carbamoyl moiety derived from an amino group of the compound.
• any physiologically acceptable equivalents of the present compounds, similar to the metabolically labile esters or carbamates, which are capable of producing the parent compounds described herein in vivo, are within the scope of this invention.
• salts of the compounds of the invention may be derived from inorganic or organic acids and bases.
• suitable salts see, e.g., Berge et al (1977) J. Pharm. Sci. 66:1; and Remington: The Science and Practice of Pharmacy, 20th Ed., ed. A. Gennaro, Lippincott Williams & Wilkins, 2000.
• the term "pharmaceutically acceptable carrier” is intended to include, but is not limited to, a material that is compatible with a recipient subject, such as a mammal (e.g., a human), and is suitable for delivering an active agent to the target site without terminating the activity of the agent.
• a mammal e.g., a human
• the toxicity or adverse effects, if any, associated with the carrier preferably are commensurate with a reasonable risk/benefit ratio for the intended use of the active agent.
• compositions of the invention can be manufactured by methods well known in the art such as conventional granulating, mixing, dissolving, encapsulating, lyophilizing, or emulsifying processes, among others.
• Compositions may be produced in various forms, including granules, precipitates, or particulates, powders, including freeze dried, rotary dried or spray dried powders, amorphous powders, tablets, capsules, syrup, suppositories, injections, emulsions, elixirs, suspensions or solutions.
• Formulations may optionally contain stabilizers, pH modifiers, surfactants, solubilizing agents, bioavailability modifiers and combinations of these.
• compositions may be prepared as liquid suspensions or solutions using a liquid, such as, but not limited to, an oil, water, an alcohol, and combinations of these. Solubilizing agents such as cyclodextrins may be included. Pharmaceutically suitable surfactants, suspending agents, or emulsifying agents, may be added for oral or parenteral administration. Suspensions may include oils, e.g., peanut oil, sesame oil, cottonseed oil, corn oil, olive oil and the like. Suspension preparations may also contain esters of fatty acids such as ethyl oleate, isopropyl myristate, fatty acid glycerides and acetylated fatty acid glycerides.
• Suspension formulations may include alcohols including, but not limited to, ethanol, isopropyl alcohol, hexadecyl alcohol, glycerol and propylene glycol.
• Ethers including, but not limited to, poly(ethyleneglycol), petroleum hydrocarbons such as mineral oil and petrolatum; and water may also be used in suspension formulations.
• compositions include, but are not limited to, ion exchangers, alumina, aluminum stearate, lecithin, serum proteins, such as human serum albumin, buffer substances such as phosphates and carbonates, glycine, sorbic acid, potassium sorbate, partial glyceride mixtures of saturated vegetable fatty acids, water, salts or electrolytes, such as protamine sulfate, disodium hydrogen phosphate, potassium hydrogen phosphate, sodium chloride, zinc salts, colloidal silica, magnesium trisilicate, polyvinyl pyrrolidone, cellulose-based substances, polyethylene glycol, sodium carboxymethylcellulose, polyacrylates, waxes, polyethylene-polyoxypropylene-block polymers, polyethylene glycol and wool fat.
• ion exchangers alumina, aluminum stearate, lecithin
• serum proteins such as human serum albumin
• buffer substances such as phosphates and carbonates
• compositions of this invention are formulated for pharmaceutical administration to a mammal, such as a human.
• Such pharmaceutical compositions may be administered orally, parenterally, by inhalation spray, topically, rectally, nasally, buccally, vaginally or via an implanted reservoir.
• parenteral includes, but is not limited to, subcutaneous, intravenous, intraperitoneal, intramuscular, intra-articular, intra-synovial, intrasternal, intrathecal, intrahepatic, intralesional and intracranial injection or infusion techniques.
• the compositions are administered orally, intravenously, or subcutaneously.
• compositions described herein may be aqueous or oleaginous suspensions. These suspensions may be formulated according to techniques known in the art using suitable dispersing or wetting agents and suspending agents.
• sterile injectable preparation may also be a sterile injectable solution or suspension in a non-toxic parenterally acceptable diluent or solvent, for example as a solution in 1,3-butanediol.
• Suitable vehicles and solvents that may be employed are water, Ringer's solution and isotonic sodium chloride solution.
• sterile, fixed oils are conventionally employed as a solvent or suspending medium.
• any bland fixed oil may be employed including synthetic mono- or di-glycerides.
• Fatty acids, such as oleic acid and its glyceride derivatives are useful in the preparation of injectables, as are natural pharmaceutically-acceptable oils, such as olive oil or castor oil, especially in their polyoxyethylated versions.
• oil solutions or suspensions may also contain a long-chain alcohol diluent or dispersant, such as carboxymethyl cellulose or similar dispersing agents which are commonly used in the formulation of pharmaceutically acceptable dosage forms including emulsions and suspensions.
• a long-chain alcohol diluent or dispersant such as carboxymethyl cellulose or similar dispersing agents which are commonly used in the formulation of pharmaceutically acceptable dosage forms including emulsions and suspensions.
• Other commonly used surfactants such as Tweens, and other emulsifying agents or bioavailability enhancers which are commonly used in the manufacture of pharmaceutically acceptable solid, liquid, or other dosage forms may also be used for the purposes of formulation.
• Compounds may be formulated for parenteral administration by injection such as by bolus injection or continuous infusion.
• a unit dosage form for injection may be in ampoules or in multi-dose containers.
• compositions may be orally administered in any orally acceptable dosage form including, but not limited to, capsules, tablets, aqueous suspensions or solutions.
• carriers that are commonly used include lactose and corn starch.
• Lubricating agents such as magnesium stearate, are also typically added.
• useful diluents include lactose and dried cornstarch.
• aqueous suspensions are required for oral use, the active ingredient is combined with emulsifying and suspending agents. If desired, certain sweetening, flavoring or coloring agents may also be added.
• pharmaceutical compositions may be administered in the form of suppositories for rectal administration.
• These may be prepared by mixing the agent with a suitable non-irritating excipient which is solid at room temperature but liquid at rectal temperature and therefore will melt in the rectum to release the drug.
• suitable non-irritating excipient include cocoa butter, beeswax and polyethylene glycols.
• compositions of this invention may also be administered topically, especially when the target of treatment includes areas or organs readily accessible by topical application, including diseases of the eye, the skin, or the lower intestinal tract. Suitable topical formulations are readily prepared for each of these areas or organs.
• Topical application for the lower intestinal tract may be effected in a rectal suppository formulation (see above) or in a suitable enema formulation. Topically- transdermal patches may also be used.
• the pharmaceutical compositions may be formulated in a suitable ointment containing the active component suspended or dissolved in one or more carriers.
• Carriers for topical administration of compounds described herein include, but are not limited to, mineral oil, liquid petrolatum, white petrolatum, propylene glycol, polyoxyethylene, polyoxypropylene compound, emulsifying wax and water.
• the pharmaceutical compositions may be formulated in a suitable lotion or cream containing the active components suspended or dissolved in one or more pharmaceutically acceptable carriers. Suitable carriers include, but are not limited to, mineral oil, sorbitan monostearate, polysorbate 60, cetyl esters wax, cetearyl alcohol, 2-octyldodecanol, benzyl alcohol and water.
• the pharmaceutical compositions may be formulated as micronized suspensions in isotonic, pH adjusted sterile saline, or, preferably, as solutions in isotonic, pH adjusted sterile saline, either with our without a preservative such as benzylalkonium chloride.
• the pharmaceutical compositions may be formulated in an ointment such as petrolatum.
• compositions may also be administered by nasal aerosol or inhalation.
• Such compositions are prepared according to techniques well known in the art of pharmaceutical formulation and may be prepared as solutions in saline, employing benzyl alcohol or other suitable preservatives, absorption promoters to enhance bioavailability, fluorocarbons, and/or other conventional solubilizing or dispersing agents.
• compositions described herein are particularly useful in therapeutic applications relating to disorders as described herein (e.g., proliferation disorders, e.g., cancers, inflammatory disorders, neurodegenerative disorders).
• the composition is formulated for administration to a patient having or at risk of developing or experiencing a recurrence of the relevant disorder being treated.
• patient as used herein, is intended to refer to an animal, e.g., a mammal such as a human.
• a pharmaceutical composition described herein may further comprise another therapeutic agent.
• the therapeutic agent can be one normally administered to patients with the disorder, disease or condition being treated.
• terapéuticaally effective amount is meant an amount of compound or composition sufficient, upon single or multiple dose administration, to cause a detectable decrease in one or more Uba6 enzyme activities and/or the severity of one or more disorders or disease states being treated.
• “Therapeutically effective amount” is also intended to include an amount sufficient to treat a cell, prolong or prevent advancement of the disorder or disease state being treated (e.g., prevent additional tumor growth of a cancer, prevent additional inflammatory response), ameliorate, alleviate, relieve, or improve a subject's symptoms of the a disorder beyond that expected in the absence of such treatment.
• a Uba6 enzyme modulator e.g., inhibitor
• a therapeutically effective amount of compound can range from about 0.001 to 30 mg/kg body weight, about 0.01 to 25 mg/kg body weight, about 0.1 to 20 mg/kg body weight, about 1 to 10 mg/kg, 2 to 9 mg/kg, 3 to 8 mg/kg, 4 to 7 mg/kg, or 5 to 6 mg/kg body weight.
• a specific dosage and treatment regimen for any particular patient will depend upon a variety of factors, including the activity of the specific compound employed, the age, body weight, general health, sex, and diet of the patient, time of administration, rate of excretion, drug combinations, the judgment of the treating physician, and the severity of the particular disease being treated.
• the amount of additional therapeutic agent present in a composition typically will be no more than the amount that would normally be administered in a composition comprising that therapeutic agent as the only active agent.
• the amount of additional therapeutic agent will range from about 50% to about 100% of the amount normally present in a composition comprising that agent as the only therapeutically active agent.
• One embodiment of the invention relates to a method of modulating (e.g., inhibiting) or decreasing one or more Uba6 enzyme activities in a sample comprising contacting the sample with one or more compounds and/or compositions described herein.
• the sample can include, without limitation, a purified or partially purified Uba6 enzyme, cultured cells or extracts of cell cultures, biopsied cells or fluid obtained from a mammal or extracts thereof, and one or more bodily fluids (e.g., blood, serum, saliva, urine, feces, semen, tears, breast milk and the like) or extracts thereof.
• Inhibition of one or more Uba6 enzyme activities in a sample may be carried out in vitro, in vivo or in situ.
• method for treating a patient having one or more ubiquitin- related disorders described herein, one or more symptoms of one or more ubiquitin- related disorders described herein, and/or at risk of developing or experiencing a recurrence of one or more ubiquitin-related disorders described herein comprise administering to the patient one or more compounds and/or pharmaceutical composition described herein.
• treating is intended to include, but is not limited to, curing, healing, alleviating, relieving, altering, remedying, ameliorating, palliating, improving or affecting the disorder, one or more symptoms of the disorder or the predisposition toward the disorder.
• one or more Uba6 enzyme inhibitors are administered in conjunction with additional therapeutic agent or agents.
• the additional therapeutic agent is one that is normally administered to patients with the disorder or condition being treated.
• the one or more Uba6 inhibitors may be administered with the other therapeutic agent in a single dosage form or as a separate dosage form.
• the other therapeutic agent may be administered prior to, at the same time as, or following administration of the one or more Uba6 inhibitors.
• the one or more Uba6 inhibitors are administered in conjunction with one or more therapeutic agents including, but not limited to, cytotoxic agents, radiotherapy, and immunotherapy appropriate for treatment of proliferative disorders and cancer.
• cytotoxic agents suitable for use in combination with the one or more Uba6 inhibitors include antimetabolites (e.g., capecitibine, gemcitabine, 5-fluorouracil or 5- fluorouracil/leucovorin, fludarabine, cytarabine, mercaptopurine, thioguanine, pentostatin, and methotrexate); topoisomerase inhibitors (e.g., etoposide, teniposide, camptothecin, topotecan, irinotecan, doxorubicin, and daunorubicin); vinca alkaloids (e.g., vincristine and vinblastin; taxanes, including, e.g., pac
• anti-inflammatory agents e.g., corticosteroids, TNF blockers, II- 1 RA, azathioprine, cyclophosphamide, and sulfasalazin
• the invention provides methods (also referred to herein as a "screening assays") for identifying modulators, i.e., candidate or test compounds or agents (e.g., peptides, cyclic peptides, peptidomimetics, small molecules, small organic molecules, or other drugs) which bind to one or more Uba6 enzymes, or have a stimulatory or inhibitory effect on Uba6 expression or on one or more Uba6 activities.
• modulators i.e., candidate or test compounds or agents (e.g., peptides, cyclic peptides, peptidomimetics, small molecules, small organic molecules, or other drugs) which bind to one or more Uba6 enzymes, or have a stimulatory or inhibitory effect on Uba6 expression or on one or more Uba6 activities.
• small organic molecule refers to an organic molecule, either naturally occurring or synthetic, that has a molecular weight of more than about 25 daltons and less than about 3000 daltons, preferably less than about 2500 daltons, more preferably less than about 2000 daltons, preferably between about 100 to about 1000 daltons, more preferably between about 200 to about 500 daltons.
• test compounds for screening candidate or test compounds which bind to or modulate the activity of Uba6, a Uba6 polypeptide or biologically active portion thereof, E2Z, or an E2Z polypeptide or biologically active portion thereof are provided.
• the test compounds can be obtained using any of the numerous approaches in combinatorial library methods known in the art, including: biological libraries; spatially addressable parallel solid phase or solution phase libraries; synthetic library methods requiring deconvolution; the "one-bead one-compound” library method; and synthetic library methods using affinity chromatography selection.
• the biological library approach is limited to peptide libraries, while the other four approaches are applicable to peptide, non-peptide oligomer or small molecule libraries of compounds (Lam, K. S. (1997) Anticancer Drug Des. 12:145).
• a molecular library of randomized nucleic acids can provide for the direct selection of candidate or test compounds with desired phenotypic effects.
• the general method can involve, for instance, expressing a molecular library of randomized nucleic acids in a plurality of cells, each of the nucleic acids comprising a different nucleotide sequence, screening for a cell of exhibiting a changed physiology in response to the presence in the cell of a candidate or test compound, and detecting and isolating the cell and/or candidate or test compound.
• the introduced nucleic acids are randomized and expressed in the cells as a library of isolated randomized expression products, which may be nucleic acids, such as mRNA, RNAi reagents, antisense RNA, siRNA, ribozyme components, etc., or peptides (e.g., cyclic peptides).
• nucleic acids such as mRNA, RNAi reagents, antisense RNA, siRNA, ribozyme components, etc., or peptides (e.g., cyclic peptides).
• RNAi reagents include, but are not limited to, double-stranded or hairpin sequences corresponding to the coding sequence of Uba6 (e.g., a nucleic acid sequence corresponding to the cysteine 625 region of human Uba6 (SEQ ID NO:5) (e.g., the catalytic cysteine domain); a nucleic acid sequence corresponding to amino acids 947 to 1052 of human Uba6 (SEQ ID NO:5) (e.g., the C-terminal ubiquitin-like (UbI) domain); an adenylate domain; and/or one or two ThiF domains).
• Uba6 e.g., a nucleic acid sequence corresponding to the cysteine 625 region of human Uba6 (SEQ ID NO:5) (e.g., the catalytic cysteine domain); a nucleic acid sequence corresponding to amino acids 947 to 1052 of human Uba6 (SEQ ID NO:5) (e.g.,
• the library should provide a sufficiently structurally diverse population of randomized expression products to effect a probabilistically sufficient range of cellular responses to provide one or more cells exhibiting a desired response.
• the introduced nucleic acids and resultant expression products are randomized, meaning that each nucleic acid and peptide consists of essentially random nucleotides and amino acids, respectively.
• the library may be fully random or biased, e.g. in nucleotide/residue frequency generally or per position.
• the nucleotides or residues are randomized within a defined class, e.g. of hydrophobic amino acids, of purines, etc.
• Functional and structural isolation of the randomized expression products may be accomplished by providing free (i.e., not covalently coupled) expression product, though in some situations, the expression product may be coupled to a functional group or fusion partner, preferably a heterologous (to the host cell) or synthetic (not native to any cell) functional group or fusion partner.
• Exemplary groups or partners include, but are not limited to, signal sequences capable of constitutively localizing the expression product to a predetermined subcellular locale such as the Golgi, endoplasmic reticulum, nucleoli, nucleus, nuclear membrane, mitochondria, chloroplast, secretory vesicles, lysosome, and the like; binding sequences capable of binding the expression product to a predetermined protein while retaining bioactivity of the expression product; sequences signaling selective degradation, of itself or co- bound proteins; and secretory and membrane-anchoring signals.
• a partner which conformationally restricts the randomized expression product to more specifically define the number of structural conformations available to the cell.
• a partner may be a synthetic presentation structure: an artificial polypeptide capable of intracellularly presenting a randomized peptide as a conformation-restricted domain.
• presentation structures comprise a first portion joined to the N-terminal end of the randomized peptide, and a second portion joined to the C-terminal end of the peptide.
• Exemplary presentation structures maximize accessibility to the peptide by presenting it on an exterior loop, for example of coiled-coils (Myszka and Chaiken (1994) Biochemistry 33:2362).
• the presentation structures are selected or designed to have minimal biologically active as expressed in the target cell.
• the presentation structures may be modified, randomized, and/or matured to alter the presentation orientation of the randomized expression product.
• determinants at the base of the loop may be modified to slightly modify the internal loop peptide tertiary structure, while maintaining the absolute amino acid identity.
• Other presentation structures include zinc-finger domains, loops on beta-sheet turns and coiled-coil stem structures in which non-critical residues are randomized; loop structures held together by cysteine bridges, cyclic peptides, etc.
• an assay is a cell-based assay in which a cell which expresses a Uba6 protein or biologically active portion thereof is contacted with a test compound and the ability of the test compound to modulate one or more Uba6 activities, e.g., ubiquitin activation; ubiquitin-adenylate intermediate formation; ubiquitin thiol esterification; ubiquitin transfer to one or more ubiquitin-conjugating enzymes (e.g., E2s); and/or ubiquitination of one or more target polypeptides is determined.
• ubiquitin activation e.g., ubiquitin activation
• ubiquitin-adenylate intermediate formation e.g., ubiquitin thiol esterification
• ubiquitin transfer to one or more ubiquitin-conjugating enzymes e.g., E2s
• ubiquitination of one or more target polypeptides is determined.
• an assay is a cell-based assay in which a cell which expresses a E2Z protein or biologically active portion thereof is contacted with a test compound and the ability of the test compound to modulate one or more E2Z activities, e.g., ubiquitin activation; ubiquitin-adenylate intermediate formation; ubiquitin thiol esterification; ubiquitin transfer to one or more ubiquitin-protein ligases (e.g., E3s); and/or ubiquitination of one or more target polypeptides is determined.
• E2Z activities e.g., ubiquitin activation; ubiquitin-adenylate intermediate formation; ubiquitin thiol esterification; ubiquitin transfer to one or more ubiquitin-protein ligases (e.g., E3s); and/or ubiquitination of one or more target polypeptides is determined.
• Determining the ability of the test compound to modulate one or more Uba6 activities and/or one or more E2Z activities can be accomplished by monitoring, for example, ubiquitin activation, formation of a ubiquitin-adenylate intermediate, ubiquitin thiol esterification, ubiquitin transfer to one or more ubiquitin-conjugating enzymes, ubiquitin transfer to one or more ubiquitin-protein ligases and/or ubiquitination of one or more target proteins or polypeptides using, for example, one or more of the assays described herein.
• Determining the ability of the test compound to modulate one or more Uba6 and/or E2Z activities can be accomplished, for example, by coupling Uba6 or a Uba6 substrate (e.g., ubiquitin, an E2 and/or a target polypeptide or protein) and/or E2Z or an E2Z substrate (e.g., ubiquitin, an E3 and/or a target polypeptide or protein) with a radioisotope or enzymatic label such that alteration of Uba6, Uba6 substrate, E2Z and/or a E2Z substrate (e.g., by ubiquitination, thiol esterification, ubiquitin adenylation or the like) can be determined by detecting an alteration of the Uba6, Uba6 substrate, E2Z and/or a E2Z substrate (e.g., altered mobility on an SDS-PAGE gel).
• Uba6 substrate e.g., ubiquitin
• compounds can be labeled with 125 1, 35 S, 14 C, or 3 H, either directly or indirectly, and the radioisotope detected by direct counting of radioemmission or by scintillation counting.
• compounds can be enzymatically labeled with, for example, horseradish peroxidase, alkaline phosphatase, or luciferase, and the enzymatic label detected by determination of conversion of an appropriate substrate to product.
• a microphysiometer can be used to detect the interaction of a compound with Uba6 and/or E2Z without the labeling of either the compound or Uba6 and/or E2Z (McConnell, H. M. et al. (1992) Science 257:1906).
• a "microphysiometer” e.g., Cytosensor
• LAPS light-addressable potentiometric sensor
• an assay is a cell-based assay comprising contacting a cell expressing Uba6 and/or E2Z (e.g., ubiquitin, an E2, an E3 a target polypeptide or protein) with a test compound and determining the ability of the test compound to modulate (e.g., stimulate or inhibit) the activity of Uba6, a Uba6 target molecule, E2Z and/or an E2Z target molecule.
• Uba6 and/or E2Z e.g., ubiquitin, an E2, an E3 a target polypeptide or protein
• Determining the ability of the test compound to modulate the activity of Uba6, a Uba6 target molecule, E2Z and/or an E2Z target molecule can be accomplished, for example, by determining the ability of the Uba6 and/or the E2Z to bind to modulate ubiquitin activation.
• Determining the ability of Uba6 and/or E2Z to modulate ubiquitin activation can be accomplished by one of the methods described above for determining direct binding.
• determining the ability of Uba6 and/or E2Z to modulate ubiquitin activation can be accomplished by detecting one or more Uba6 and/or E2Z activities, e.g., ubiquitin activation; ubiquitin-adenylate intermediate formation; ubiquitin thiol esterif ⁇ cation; ubiquitin transfer to one or more ubiquitin- conjugating enzymes (e.g., E2s); ubiquitin transfer to one or more ubiquitin-protein ligases (e.g., E3s); and/or ubiquitination of one or more target polypeptides (e.g., ubiquitin, an E2, an E3, a target polypeptide and/or protein or the like).
• ubiquitin activation e.g., ubiquitin activation;
• an assay of the present invention is a cell-free assay in which Uba6 and/or E2Z is contacted with a test compound and the ability of the test compound to bind to Uba6 and/or E2Z or a biologically active portion of Uba6 and/or E2Z is determined.
• Biologically active portions of Uba6 to be used in assays of the present invention include, but are not limited to, ThiF domains (e.g., amino acids 50- 200 and 460-600 of SEQ ID NO:5, for ThiF domain 1 and ThiF domain 2, respectively), catalytic cysteine domains (e.g., amino acid sequences including cysteine 625 of SEQ ID NO:5), adenylate domains (e.g., amino acids 1-610 of SEQ ID NO:5), C-terminal ubiquitin-like (UbI) domains (e.g., amino acids 947-1052 of SEQ ID NO:5), and the like.
• ThiF domains e.g., amino acids 50- 200 and 460-600 of SEQ ID NO:5, for ThiF domain 1 and ThiF domain 2, respectively
• catalytic cysteine domains e.g., amino acid sequences including cysteine 625 of SEQ ID NO:5
• adenylate domains e.g.,
• Binding of the test compound to Uba6 and/or E2Z can be determined either directly or indirectly as described above.
• the assay includes contacting Uba6 and/or E2Z or biologically active portion of Uba6 and/or E2Z with a known compound which binds Uba6 and/or E2Z to form an assay mixture, contacting the assay mixture with a test compound, and determining the ability of the test compound to interact with Uba6 and/or E2Z, wherein determining the ability of the test compound to interact with Uba6 and/or E2Z comprises determining the ability of the test compound to preferentially bind to Uba6 and/or E2Z or a biologically active portion of Uba6 and/or E2Z as compared to the known compound.
• the assay is a cell-free assay in which Uba6 and/or E2Z or a biologically active portion of Uba6 and/or E2Z is contacted with a test compound and the ability of the test compound to modulate (e.g., stimulate or inhibit) the activity of Uba6 and/or E2Z or a biologically active portion of Uba6 and/or E2Z is determined. Determining the ability of the test compound to modulate the activity of Uba6 and/or E2Z can be accomplished, for example, by determining the ability of Uba6 and/or E2Z to bind to a Uba6 and/or an E2Z target molecule by one of the methods described above for determining direct binding.
• Determining the ability of Uba6 and/or E2Z to bind to a Uba6 and/or E2Z target molecule, respectively, can also be accomplished using a technology such as real-time Biomolecular Interaction Analysis (BIA) (Sjolander, S. and Urbaniczky, C. (1991) Anal. Chem. 63:2338-2345 and Szabo et al. (1995) Curr. Opin. Struct. Biol. 5:699-705).
• BIOA Biomolecular Interaction Analysis
• BIA is a technology for studying biospecif ⁇ c interactions in real time, without labeling any of the interactants (e.g., BIAcore). Changes in the optical phenomenon of surface plasmon resonance (SPR) can be used as an indication of real-time reactions between biological molecules.
• the cell-free assay involves contacting Uba6 and/or E2Z or a biologically active portion of Uba6 and/or E2Z with a known compound which binds Uba6 and/or E2Z, respectively, to form an assay mixture, contacting the assay mixture with a test compound, and determining the ability of the test compound to interact with Uba6 and/or E2Z, wherein determining the ability of the test compound to interact with Uba6 and/or E2Z comprises determining the ability of Uba6 and/or E2Z to preferentially bind to or modulate the activity of a Uba6 and/or E2Z target molecule (e.g., ubiquitin activation; ubiquitin-adenylate intermediate formation; ubiquitin thiol esterif ⁇ cation; ubiquitin transfer to one or more ubiquitin-conjugating enzymes (e.g., E2s); ubiquitin transfer to one or
• ubiquitin activation
• Uba6, a Uba6 target molecule, E2Z and/or an E2Z target molecule may be desirable to immobilize either Uba6, a Uba6 target molecule, E2Z and/or an E2Z target molecule to facilitate separation of complexed from uncomplexed forms of one or both of the proteins, as well as to accommodate automation of the assay.
• Binding of a test compound to Uba6 and/or E2Z, or interaction of Uba6 and/or E2Z with one or more target molecules in the presence and absence of a candidate compound can be accomplished in any vessel suitable for containing the reactants. Examples of such vessels include microtitre plates, test tubes, and microfuge tubes.
• a fusion protein can be provided which adds a domain that allows one or both of the proteins to be bound to a matrix.
• glutathione- S- transferase/Uba ⁇ fusion proteins or glutathione-S-transferase/target fusion proteins can be adsorbed onto glutathione sepharose beads (Sigma, St. Louis, MO) or glulathione-derivatized microtitre plates, which are then combined with the test compound or the test compound and either the non-adsorbed target protein or Uba6, and the mixture incubated under conditions conducive to complex formation (e.g., at physiological conditions for salt and pH).
• the beads or microtitre plate wells are washed to remove any unbound components, the matrix immobilized in the case of beads, complex determined either directly or indirectly, for example, as described above.
• the complexes can be dissociated from the matrix, and the level of Uba6 binding or activity determined using standard techniques.
• Uba6, a Uba6 target molecule, E2Z and/or an E2Z target molecule can be immobilized utilizing conjugation of biotin and avidin or streptavidin.
• Biotinylated Uba6 and/or E2Z or target molecules can be prepared from biotin-NHS (N-hydroxy-succinimide) using techniques known in the art (e.g., biotinylation kit, Pierce Chemicals, Rockford, IL), and immobilized in the wells of streptavidin-coated 96 well plates (Pierce).
• antibodies reactive with Uba6 and/or E2Z or target molecules that do not interfere with binding of Uba6 and/or E2Z to its target molecule can be derivatized to the wells of the plate, and unbound target or Uba6 and/or E2Z trapped in the wells by antibody conjugation.
• Methods for detecting such complexes include immunodetection of complexes using antibodies reactive with Uba6 and/or E2Z or one or more Uba6 and/or E2Z target molecules, as well as enzyme-linked assays which rely on detecting an enzymatic activity associated with Uba6 and/or E2Z.
• modulators of Uba6 and/or E2Z expression are identified in a method wherein a cell is contacted with a candidate compound and the expression of Uba6 protein, Uba6 mRNA, E2Z protein, and/or E2Z mRNA in the cell is determined.
• the level of Uba6 protein, Uba6 mRNA, E2Z protein, and/or E2Z mRNA in the presence of the candidate compound is compared to the level of Uba6 protein, Uba6 mRNA, E2Z protein, and/or E2Z mRNA in the absence of the candidate compound.
• the candidate compound can then be identified as a modulator of Uba6 and/or E2Z protein expression and/or Uba6 and/or E2Z mRNA expression based on this comparison. For example, when expression of Uba6 and/or E2Z protein and/or Uba6 and/or E2Z mRNA is greater (statistically significantly greater) in the presence of the candidate compound than in its absence, the candidate compound is identified as a stimulator of Uba6 and/or E2Z protein expression and/or Uba6 and/or E2Z mRNA expression, respectively.
• the candidate compound when expression of Uba6 and/or E2Z protein and/or Uba6 and/or E2Z mRNA is less (statistically significantly less) in the presence of the candidate compound than in its absence, the candidate compound is identified as an inhibitor of Uba6 and/or E2Z protein expression and/or Uba6 and/or E2Z mRNA expression, respectively.
• the level of Uba6 and/or E2Z mRNA or protein expression in the cells can be determined by methods described herein for detecting Uba6 and/or E2Z mRNA or protein.
• Uba6 and/or E2Z can be used as "bait proteins" in a two-hybrid assay or three-hybrid assay (see, e.g., U.S. Patent No. 5,283,317; Zervos et al. (1993) Cell 72:223-232; Madura et al. (1993) J. Biol. Chem. 268:12046- 12054; Bartel et al. (1993) Biotechniques 14:920-924; Iwabuchi et al.
• Uba6-binding proteins proteins which bind to or interact with Uba6
• Uba6 activities e.g., ubiquitin activation; ubiquitin-adenylate intermediate formation; ubiquitin thiol esterification; ubiquitin transfer to one or more ubiquitin- conjugating enzymes (e.g., E2s); and/or ubiquitination of one or more target polypeptides (e.g., ubiquitin, an E2, a target polypeptide and/or protein or the like)
• target polypeptides e.g., ubiquitin, an E2, a target polypeptide and/or protein or the like
• target polypeptides e.g., ubiquitin, an E2, a target polypeptide and/or protein or the like
• an assay is an animal model based assay comprising contacting a an animal with a test compound and determining the ability of the test compound to alter Uba6 and/or E2Z expression and/or Uba6 and/or E2Z activity.
• Animals include, but are not limited to, mammals such as non-human primates, rabbits, rats, mice, and the like.
• This invention further pertains to novel agents identified by the above-described screening assays. Accordingly, it is within the scope of this invention to further use an agent identified as described herein in an appropriate animal model as described herein.
• an agent identified as described herein e.g., a Uba6 and/or E2Z modulating agent
• an agent identified as described herein can be used in an animal model to determine the efficacy, toxicity, or side effects of treatment with such an agent.
• an agent identified as described herein can be used in an animal model to determine the mechanism of action of such an agent.
• this invention pertains to uses of novel agents identified by the above-described screening assays for treatments of ubiquitin-related disorders (e.g., cellular proliferative disorders and/or neurodegenerative disorders) described herein.
• One aspect of the invention pertains to isolated nucleic acid molecules that encode Uba ⁇ and/or E2Z proteins or biologically active portions thereof, as well as nucleic acid fragments sufficient for use as hybridization probes to identify Uba ⁇ - and/or E2Z-encoding nucleic acid molecules (e.g., Uba ⁇ and/or E2Z mRNA, respectively) and fragments for use as PCR primers for the amplification or mutation of Uba ⁇ nucleic acid molecules.
• nucleic acid molecule is intended to include, but is not limited to, DNA molecules (e.g., cDNA or genomic DNA) and RNA molecules (e.g., mRNA) and analogs of the DNA or RNA generated using nucleotide analogs.
• the nucleic acid molecule can be single-stranded or double- stranded DNA.
• an "isolated" nucleic acid molecule is one which is separated from other nucleic acid molecules which are present in the natural source of the nucleic acid.
• an "isolated" nucleic acid is free of sequences which naturally flank the nucleic acid (i.e., sequences located at the 5' and 3' ends of the nucleic acid) in the genomic DNA of the organism from which the nucleic acid is derived.
• the isolated Uba ⁇ nucleic acid molecule can contain less than about 5 kb, 4 kb, 3 kb, 2 kb, 1 kb, 0.5 kb or 0.1 kb of nucleotide sequences which naturally flank the nucleic acid molecule in genomic DNA of the cell from which the nucleic acid is derived.
• an "isolated" nucleic acid molecule such as a cDNA molecule, can be substantially free of other cellular material, or culture medium when produced by recombinant techniques, or substantially free of chemical precursors or other chemicals when chemically synthesized.
• a nucleic acid molecule of the present invention e.g., a nucleic acid molecule having the nucleotide sequence of SEQ ID NO:4 or SEQ ID NO:6, or a portion thereof, can be isolated using standard molecular biology techniques and the sequence information provided herein. Using all or portion of the nucleic acid sequence of SEQ ID NO:4 or SEQ ID NO: 6 as a hybridization probe, Uba6 nucleic acid molecules can be isolated using standard hybridization and cloning techniques (e.g., as described in Sambrook, J., Fritsh, E.
• nucleic acid molecule encompassing all or a portion of SEQ ID NO:4 or SEQ ID NO:6 can be isolated by the polymerase chain reaction (PCR) using synthetic oligonucleotide primers designed based upon the sequence of SEQ ID NO:4 or SEQ ID NO:6.
• a nucleic acid of the invention can be amplified using cDNA, mRNA or alternatively, genomic DNA, as a template and appropriate oligonucleotide primers according to standard PCR amplification techniques.
• the nucleic acid so amplified can be cloned into an appropriate vector and characterized by DNA sequence analysis.
• oligonucleotides corresponding to Uba6 and/or E2Z nucleotide sequences can be prepared by standard synthetic techniques, e.g., using an automated DNA synthesizer.
• an isolated nucleic acid molecule of the invention comprises the nucleotide sequence shown in SEQ ID NO:4 or SEQ ID NO:6, or a portion of either of these nucleotide sequences.
• an isolated nucleic acid molecule of the invention comprises a nucleic acid molecule which is a complement of the nucleotide sequence shown in SEQ ID NO:4 or SEQ ID NO:6, or a portion of any of these nucleotide sequences.
• a nucleic acid molecule which is complementary to the nucleotide sequence shown in SEQ ID NO:4 or SEQ ID NO:6, is one which is sufficiently complementary to the nucleotide sequence shown in SEQ ID NO:4 or SEQ ID NO:6, such that it can hybridize to the nucleotide sequence shown in SEQ ID NO:4 or SEQ ID NO:6, thereby forming a stable duplex.
• an isolated nucleic acid molecule of the present invention comprises a nucleotide sequence which is at least about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or more identical to the entire length of the nucleotide sequence shown in SEQ ID NO:4 or SEQ ID NO:6, or a portion of either of these nucleotide sequences.
• the nucleic acid molecule of the invention can comprise only a portion of the nucleic acid sequence of SEQ ID NO:4 or SEQ ID NO:6, for example a fragment which can be used as a probe or primer or a fragment encoding a biologically active portion of a Uba6 protein.
• the nucleic acid sequence of SEQ ID NO:4 or SEQ ID NO: 6 allows for the generation of probes and primers designed for use in identifying and/or cloning other Uba6 family members, as well as Uba6 homologues from other species.
• the probe/primer typically comprises substantially purified oligonucleotide.
• the oligonucleotide typically comprises a region of nucleotide sequence that hybridizes under stringent conditions to at least about 12 or 15, about 20 or 25, about 30, 35, 40, 45, 50, 55, 60, 65, or 75 consecutive nucleotides of a sense sequence of SEQ ID NO:4 or SEQ ID NO:6, of an anti-sense sequence of SEQ ID NO:4 or SEQ ID NO:6, or of a naturally occurring allelic variant or mutant of SEQ ID NO:4 or SEQ ID NO:6.
• a nucleic acid molecule of the present invention comprises a nucleotide sequence which is 350-400, 400-450, 450-500, 500-550, 550-600, 600- 650, 650-700, 700-750, 750-800, 800-850, 850-900, 900-950, 950-1000, 1000-1500, 1500-2000, 2000-2500, 2500-3000, 3000-3500, 3500-4000, 4000-4500, 4500-5000, 5101, 5386, 5000-5500 or more nucleotides in length and hybridizes under stringent hybridization conditions to a nucleic acid molecule of SEQ ID NO:4 or SEQ ID NO:6.
• Probes based on the Uba6 nucleotide sequences can be used to detect transcripts or genomic sequences encoding the same or homologous proteins.
• the probe further comprises a label group attached thereto, e.g., the label group can be a radioisotope, a fluorescent compound, an enzyme, or an enzyme co-factor.
• Such probes can be used as a part of a diagnostic test kit for identifying cells or tissue which mis-express Uba6, such as by measuring a level of a Uba6- encoding nucleic acid in a sample of cells from a subject e.g., detecting Uba6 mRNA levels or determining whether a genomic Uba6 gene has been mutated or deleted.
• a nucleic acid fragment encoding a "biologically active portion of a Uba6 protein” can be prepared by isolating a portion of the nucleotide sequence of SEQ ID NO:4 or SEQ ID NO: 6 which encodes a polypeptide having a Uba6 biological activity (the biological activities of the Uba6 proteins are described herein), expressing the encoded portion of the Uba6 protein (e.g., by recombinant expression in vitro) and assessing the activity of the encoded portion of Uba6.
• the invention further encompasses nucleic acid molecules that differ from the nucleotide sequence shown in SEQ ID NO:4 or SEQ ID NO:6 due to degeneracy of the genetic code and thus encode the same Uba6 proteins as those encoded by the nucleotide sequence shown in SEQ ID NO:4 or SEQ ID NO:6.
• an isolated nucleic acid molecule of the invention has a nucleotide sequence encoding a protein having an amino acid sequence shown in SEQ ID NO: 5 or SEQ ID NO:7.
• Uba6 nucleotide sequences of SEQ ID NO: 4 or SEQ ID NO:6 DNA sequence polymorphisms that lead to changes in the amino acid sequences of the Uba6 proteins may exist within a population (e.g., the human population). Such genetic polymorphism in the Uba6 genes may exist among individuals within a population due to natural allelic variation.
• the terms "gene” and “recombinant gene” refer to nucleic acid molecules which include an open reading frame encoding Uba6, such as a mammalian or mouse or zebraf ⁇ sh Uba6, and can further include non-coding regulatory sequences, and introns.
• Allelic variants of Uba6 include both functional and non- functional Uba6 proteins.
• Functional allelic variants are naturally occurring amino acid sequence variants of the Uba6 that maintain the ability to bind a Uba6 ligand and/or modulate any of the Uba6 activities described herein.
• Functional allelic variants will typically contain only conservative substitution of one or more amino acids of SEQ ID NO: 5 or SEQ ID NO: 7 or substitution, deletion or insertion of non-critical residues in non-critical regions of the protein.
• Non- functional allelic variants are naturally occurring amino acid sequence variants of the Uba6 that do not have the ability to either bind a Uba6 ligand and/or modulate any of the Uba6 activities described herein.
• Non-functional allelic variants will typically contain a non-conservative substitution, a deletion, or insertion or premature truncation of the amino acid sequence of SEQ ID NO:5 or SEQ ID NO:7 or a substitution, insertion or deletion in critical residues or critical regions.
• the present invention further provides non-human orthologs of a Uba6 protein.
• Orthologs of a Uba6 protein are proteins that are isolated from various organisms that possess the same Uba6 ligand binding and/or modulation of any of the Uba6 activities described herein.
• Orthologs of Uba6 can readily be identified as comprising an amino acid sequence that is substantially identical to SEQ ID NO: 5 or SEQ ID NO:7.
• nucleic acid molecules encoding other Uba6 family members and, thus, which have a nucleotide sequence which differs from the Uba6 sequences of SEQ ID NO:4 or SEQ ID NO:6 are intended to be within the scope of the invention.
• another Uba6 cDNA can be identified based on the nucleotide sequence of human or mouse Uba6.
• nucleic acid molecules encoding Uba6 proteins from different species, and thus which have a nucleotide sequence which differs from the Uba6 sequences of SEQ ID NO:4 or SEQ ID NO:6 are intended to be within the scope of the invention.
• a monkey Uba6 cDNA can be identified based on the nucleotide sequence of a human or mouse Uba6.
• nucleic acid molecules corresponding to natural allelic variants and homologues of the Uba6 cDNAs of the invention can be isolated based on their homology to the Uba6 nucleic acids disclosed herein using the cDNAs disclosed herein, or a portion thereof, as a hybridization probe according to standard hybridization techniques under stringent hybridization conditions.
• an isolated nucleic acid molecule of the invention is at least 15, 20, 25, 30 or more nucleotides in length and hybridizes under stringent conditions to the nucleic acid molecule comprising the nucleotide sequence of SEQ ID NO:4 or SEQ ID NO:6.
• the nucleic acid is at least 30, 50, 100, 150, 200, 250, 300, 307, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5101, 5386, or 5500 nucleotides in length.
• hybridizes under stringent conditions is intended to describe conditions for hybridization and washing under which nucleotide sequences at least 60% identical to each other typically remain hybridized to each other.
• the conditions are such that sequences at least about 70%, at least about 80%, at least about 85%, at least about 90% or 95% identical to each other typically remain hybridized to each other.
• stringent conditions are known to those skilled in the art and can be found in Current Protocols in Molecular Biology, John Wiley & Sons, N.Y. (1989), 6.3.1- 6.3.6.
• a non-limiting example of stringent hybridization conditions are hybridization in 6X sodium chloride/sodium citrate (SSC) at about 45 0 C, followed by one or more washes in 0.2X SSC, 0.1% SDS at 50 0 C, in certain aspects at 55 0 C, and in other aspects at 60 0 C or 65 0 C.
• an isolated nucleic acid molecule of the invention that hybridizes under stringent conditions to the sequence of SEQ ID NO:4 or SEQ ID NO: 6 corresponds to a naturally-occurring nucleic acid molecule.
• a "naturally-occurring" nucleic acid molecule refers to an RNA or DNA molecule having a nucleotide sequence that occurs in nature (e.g., encodes a natural protein).
• allelic variants of the Uba6 sequences that may exist in the population, the skilled artisan will further appreciate that changes can be introduced by mutation into the nucleotide sequences of SEQ ID NO:4 or SEQ ID NO:6, thereby leading to changes in the amino acid sequence of the encoded Uba6 proteins, without altering the functional ability of the Uba6 proteins.
• nucleotide substitutions leading to amino acid substitutions at "non-essential" amino acid residues can be made in the sequence of SEQ ID NO:4 or SEQ ID NO:6.
• non-essential amino acid residue is a residue that can be altered from the wild-type sequence of Uba6 (e.g., the sequence of SEQ ID NO:5 or SEQ ID NO:7) without altering the biological activity, whereas an "essential" amino acid residue is required for biological activity.
• amino acid residues that are conserved among the Uba6 proteins of the present invention are predicted to be particularly unamenable to alteration.
• additional amino acid residues that are conserved between the Uba6 proteins of the present invention and other members of the Uba6 family of proteins are not likely to be amenable to alteration.
• nucleic acid molecules encoding Uba6 proteins that contain changes in amino acid residues that are not essential for activity. Such Uba6 proteins differ in amino acid sequence from SEQ ID NO:5 or SEQ ID NO:7, yet retain biological activity.
• the isolated nucleic acid molecule comprises a nucleotide sequence encoding a protein, wherein the protein comprises an amino acid sequence at least about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or more identical to SEQ ID NO:5 or SEQ ID NO:7.
• An isolated nucleic acid molecule encoding a Uba6 protein homologous to the protein of SEQ ID NO: 5 or SEQ ID NO: 7 can be created by introducing one or more nucleotide substitutions, additions or deletions into the nucleotide sequence of SEQ ID NO:4 or SEQ ID NO:6, such that one or more amino acid substitutions, additions or deletions are introduced into the encoded protein. Mutations can be introduced into SEQ ID NO:4 or SEQ ID NO:6 by standard techniques, such as site-directed mutagenesis and PCR-mediated mutagenesis. In certain embodiments, conservative amino acid substitutions are made at one or more predicted non-essential amino acid residues.
• a “conservative amino acid substitution” is one in which the amino acid residue is replaced with an amino acid residue having a similar side chain.
• Families of amino acid residues having similar side chains have been defined in the art. These families include amino acids with basic side chains (e.g., lysine, arginine, histidine), acidic side chains (e.g., aspartic acid, glutamic acid), uncharged polar side chains (e.g., glycine, asparagine, glutamine, serine, threonine, tyrosine, cysteine), nonpolar side chains (e.g., alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine, tryptophan), beta-branched side chains (e.g., threonine, valine, isoleucine) and aromatic side chains (e.g., tyrosine, phenylalanine, tryptophan, histidine).
• a predicted nonessential amino acid residue in a Uba6 protein is replaced with another amino acid residue from the same side chain family.
• mutations can be introduced randomly along all or part of a Uba6 coding sequence, such as by saturation mutagenesis, and the resultant mutants can be screened for Uba6 biological activity to identify mutants that retain activity. Following mutagenesis of SEQ ID NO:4 or SEQ ID NO:6, the encoded protein can be expressed recombinantly and the activity of the protein can be determined.
• a mutant Uba6 protein can be assayed for the ability to (1) activate ubiquitin; (2) mediate ubiquitin-adenylate intermediate formation; (3) mediate ubiquitin thiol esterif ⁇ cation; (4) transfer ubiquitin to one or more ubiquitin- conjugating enzymes (e.g., E2s); and/or (5) ubiquitinate one or more target polypeptides (e.g., ubiquitin, an E2, a target polypeptide and/or protein or the like).
• ubiquitin- conjugating enzymes e.g., E2s
• target polypeptides e.g., ubiquitin, an E2, a target polypeptide and/or protein or the like.
• a mutant E2Z protein can be assayed for the ability to (1) activate ubiquitin; (2) mediate ubiquitin-adenylate intermediate formation; (3) mediate ubiquitin thiol esterif ⁇ cation; (4) transfer ubiquitin to one or more ubiquitin- protein ligases (e.g., E3s); and/or (5) ubiquitinate one or more target polypeptides (e.g., ubiquitin, an E3, a target polypeptide and/or protein or the like).
• ubiquitin- protein ligases e.g., E3s
• ubiquitinate one or more target polypeptides e.g., ubiquitin, an E3, a target polypeptide and/or protein or the like.
• an antisense nucleic acid comprises a nucleotide sequence which is complementary to a "sense" nucleic acid encoding a protein, e.g., complementary to the coding strand of a double-stranded cDNA molecule or complementary to an mRNA sequence. Accordingly, an antisense nucleic acid can hydrogen bond to a sense nucleic acid.
• the antisense nucleic acid can be complementary to an entire Uba6 and/or E2Z coding strand, or to only a portion thereof.
• an antisense nucleic acid molecule is antisense to a "coding region" of the coding strand of a nucleotide sequence encoding Uba6 and/or E2Z.
• coding region refers to the region of the nucleotide sequence comprising codons which are translated into amino acid residues.
• the antisense nucleic acid molecule is antisense to a "non-coding region" of the coding strand of a nucleotide sequence encoding Uba6 and/or E2Z.
• non-coding region refers to 5' and 3' sequences which flank the coding region that are not translated into amino acids (i.e., also referred to as 5' and 3' untranslated regions).
• Embodiments of the present invention provide amino acid sequences having one or more biologically active portions of a Uba6 and/or E2Z protein.
• a "biologically active portion of a Uba6 protein” includes a fragment of a Uba6 protein which participates in an interaction between a Uba6 molecule and a non-Uba6 molecule.
• a "biologically active portion of an E2Z protein” includes a fragment of a E2Z protein which participates in an interaction between an E2Z molecule and a non-E2Z molecule.
• Biologically active portions of a Uba6 protein include peptides comprising amino acid sequences sufficiently identical to or derived from the amino acid sequence of the Uba6 protein, e.g., the amino acid sequence shown in SEQ ID NO:5 or SEQ ID NO:7, which include less amino acids than a full length Uba6 protein, and exhibit at least one activity of a Uba6 protein.
• biologically active portions comprise a domain or motif (e.g., one, two or more ThiF domains, one or more catalytic cysteine domains, one or more adenylate domains and/or one or more C-terminal ubiquitin-like (UbI) domains) with at least one activity of the Uba6 protein (e.g., ubiquitin activation; ubiquitin-adenylate intermediate formation; ubiquitin thiol esterif ⁇ cation; ubiquitin transfer to one or more ubiquitin- conjugating enzymes (e.g., E2s); and/or ubiquitination of one or more target polypeptides (e.g., ubiquitin, an E2, a target polypeptide and/or protein or the like).
• ubiquitin activation ubiquitin-adenylate intermediate formation
• ubiquitin thiol esterif ⁇ cation ubiquitin transfer to one or more ubiquitin- conjugating enzymes (e.g
• a biologically active portion of a Uba6 protein can be a polypeptide which is, for example, 10, 25, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1050, 1052, 1053 or more amino acids in length.
• Biologically active portions of a Uba6 protein can be used as targets for developing agents which modulate a UPP activity.
• a biologically active portion of a Uba6 protein comprises at least one ThiF domain, catalytic cysteine domain, adenylate domain and/or a C-terminal ubiquitin-like domain.
• a biologically active portion of a Uba6 protein of the present invention may contain at least one of the above-identified structural domains.
• a biologically active portion of a Uba6 protein may contain at least two, at least three or at least four of the above -identified structural domains.
• other biologically active portions, in which other regions of the protein are deleted can be prepared by recombinant techniques and evaluated for one or more of the functional activities of a native Uba6 protein.
• the Uba6 protein has an amino acid sequence shown in SEQ ID NO: 5 or SEQ ID NO:7.
• the Uba6 protein is substantially homologous to SEQ ID NO:5 or SEQ ID NO:7, and retains the functional activity of the protein of SEQ ID NO:5 or SEQ ID NO:7, yet differs in amino acid sequence due to natural allelic variation or mutagenesis, as described in detail above.
• the Uba6 protein is a protein which comprises an amino acid sequence at least about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or more identical to SEQ ID NO:5 or SEQ ID NO:7.
• sequences are aligned for optimal comparison purposes (e.g., gaps can be introduced in one or both of a first and a second amino acid or nucleic acid sequence for optimal alignment and non-homologous sequences can be disregarded for comparison purposes).
• the length of a reference sequence aligned for comparison purposes is at least 30%, at least 40%, at least 50%, at least 60%, and even at least 70%, 80%, or 90% of the length of the reference sequence (e.g., when aligning a second sequence to the Uba6 amino acid sequence having 1052 and 1053 amino acid residues, respectively, at least 315, at least 420, at least 526, at least 631, and even at least 736, 841 or 946 amino acid residues are aligned).
• the amino acid residues or nucleotides at corresponding amino acid positions or nucleotide positions are then compared.
• amino acid or nucleic acid “identity” is equivalent to amino acid or nucleic acid "homology”).
• the percent identity between the two sequences is a function of the number of identical positions shared by the sequences, taking into account the number of gaps, and the length of each gap, which need to be introduced for optimal alignment of the two sequences.
• the comparison of sequences and determination of percent identity between two sequences can be accomplished using a mathematical algorithm.
• the percent identity between two amino acid sequences is determined using the Needleman and Wunsch (J. MoI. Biol. (48):444-453 (1970)) algorithm which has been incorporated into the GAP program in the GCG software package (available at http://www.gcg.com), using either a Blosum 62 matrix or a PAM250 matrix, and a gap weight of 16, 14, 12, 10, 8, 6, or 4 and a length weight of 1, 2, 3, 4, 5, or 6.
• the percent identity between two nucleotide sequences is determined using the GAP program in the GCG software package (available at the website gcg.com), using a NWSgapdnaCMP matrix and a gap weight of 40, 50, 60, 70, or 80 and a length weight of 1, 2, 3, 4, 5, or 6.
• the percent identity between two amino acid or nucleotide sequences is determined using the algorithm of E. Meyers and W. Miller (CABIOS (1989) 4:11) which has been incorporated into the ALIGN program (version 2.0), using a PAM 120 weight residue table, a gap length penalty of 12 and a gap penalty of 4.
• nucleic acid and protein sequences of the present invention can further be used as a "query sequence" to perform a search against public databases to, for example, identify other family members or related sequences.
• search can be performed using the NBLAST and XBLAST programs (version 2.0) of Altschul, et al. (1990) J. MoI. Biol. 215:403.
• Gapped BLAST can be utilized as described in Altschul et al., (1997) Nucleic Acids Res. 25(17):3389.
• the default parameters of the respective programs e.g., XBLAST and NBLAST
• XBLAST and NBLAST can be used (ncbi.nlm.nih.gov website).
• vectors such as expression vectors, containing a nucleic acid encoding a Uba6 and/or an E2Z protein (or a portion thereof).
• vector refers to a nucleic acid molecule capable of transporting another nucleic acid to which it has been linked.
• plasmid refers to a circular double stranded DNA loop into which additional DNA segments can be ligated.
• viral vector is another type of vector, wherein additional DNA segments can be ligated into the viral genome.
• vectors are capable of autonomous replication in a host cell into which they are introduced (e.g., bacterial vectors having a bacterial origin of replication and episomal mammalian vectors). Other vectors (e.g., non-episomal mammalian vectors) are integrated into the genome of a host cell upon introduction into the host cell, and thereby are replicated along with the host genome. Moreover, certain vectors are capable of directing the expression of genes to which they are operatively linked. Such vectors are referred to herein as "expression vectors.” In general, expression vectors of utility in recombinant DNA techniques are often in the form of plasmids.
• plasmid and "vector” can be used interchangeably as the plasmid is the most commonly used form of vector.
• the invention is intended to include such other forms of expression vectors, such as viral vectors (e.g., replication defective retroviruses, adenoviruses and adeno-associated viruses), which serve equivalent functions.
• viral vectors e.g., replication defective retroviruses, adenoviruses and adeno-associated viruses
• the recombinant expression vectors of the invention comprise a nucleic acid of the invention in a form suitable for expression of the nucleic acid in a host cell, which means that the recombinant expression vectors include one or more regulatory sequences, selected on the basis of the host cells to be used for expression, which is operatively linked to the nucleic acid sequence to be expressed.
• "operably linked" is intended to mean that the nucleotide sequence of interest is linked to the regulatory sequence(s) in a manner which allows for expression of the nucleotide sequence (e.g., in an in vitro transcription/translation system or in a host cell when the vector is introduced into the host cell).
• regulatory sequence is intended to includes promoters, enhancers and other expression control elements (e.g., polyadenylation signals). Such regulatory sequences are described, for example, in Goeddel, Gene Expression Technology: Methods in Enzymology 185, Academic Press, San Diego, CA (1990). Regulatory sequences include those which direct constitutive expression of a nucleotide sequence in many types of host cells and those which direct expression of the nucleotide sequence only in certain host cells (e.g., tissue-specific regulatory sequences). It will be appreciated by those skilled in the art that the design of the expression vector can depend on such factors as the choice of the host cell to be transformed, the level of expression of protein desired, etc.
• the expression vectors of the invention can be introduced into host cells to thereby produce proteins or peptides, including fusion proteins or peptides, encoded by nucleic acids as described herein (e.g., Uba6 and/or E2Z proteins, mutant forms of Uba6 and/or E2Z proteins, fusion proteins, and the like).
• proteins or peptides including fusion proteins or peptides, encoded by nucleic acids as described herein (e.g., Uba6 and/or E2Z proteins, mutant forms of Uba6 and/or E2Z proteins, fusion proteins, and the like).
• the recombinant expression vectors of the invention can be designed for expression of Uba6 in prokaryotic or eukaryotic cells.
• Uba6, Uba6 fragments, E2Z and/or E2Z fragments can be expressed in bacterial cells such as E. coli, insect cells (using baculovirus expression vectors), yeast cells or mammalian cells. Suitable host cells are discussed further in Goeddel, Gene Expression Technology: Methods in Enzymology 185, Academic Press, San Diego, CA (1990).
• the recombinant expression vector can be transcribed and translated in vitro, for example using T7 promoter regulatory sequences and T7 polymerase.
• Fusion vectors add a number of amino acids to a polypeptide encoded therein, usually to the amino terminus of the recombinant polypeptide.
• Such fusion vectors typically serve three purposes: 1) to increase expression of recombinant polypeptide; 2) to increase the solubility of the recombinant polypeptide; and 3) to aid in the purification of the recombinant polypeptide by acting as a ligand in affinity purification.
• a proteolytic cleavage site is introduced at the junction of the fusion moiety and the recombinant polypeptide to enable separation of the recombinant polypeptide from the fusion moiety subsequent to purification of the fusion polypeptide.
• enzymes, and their cognate recognition sequences include Factor Xa, thrombin and enterokinase.
• Typical fusion expression vectors include pGEX (Pharmacia Biotech Inc; Smith, D. B. and Johnson, K. S.
• GST glutathione S-transferase
• Examples of suitable inducible non-fusion E. coli expression vectors include pTrc (Amann et al, (1988) Gene 69:301-315) and pET 1 Id (Studier et al, Gene Expression Technology: Methods in Enzymology 185, Academic Press, San Diego, CA (1990) 60- 89).
• Target gene expression from the pTrc vector relies on host RNA polymerase transcription from a hybrid trp-lac fusion promoter.
• Target gene expression from the pET Hd vector relies on transcription from a T7 gnlO-lac fusion promoter mediated by a coexpressed viral RNA polymerase (T7 gnl). This viral polymerase is supplied by host strains BL21(DE3) or HMS174(DE3) from a resident prophage harboring a T7 gnl gene under the transcriptional control of the lacUV 5 promoter.
• One strategy to maximize recombinant protein expression in E. coli is to express the protein in a host bacteria with an impaired capacity to proteolytically cleave the recombinant protein (Gottesman, S., Gene Expression Technology: Methods in Enzymology 185, Academic Press, San Diego, CA (1990) 119-128).
• Another strategy is to alter the nucleic acid sequence of the nucleic acid to be inserted into an expression vector so that the individual codons for each amino acid are those preferentially utilized in E. coli (Wada et al., (1992) Nucleic Acids Res. 20:2111).
• Such alteration of nucleic acid sequences of the invention can be carried out by standard DNA synthesis techniques.
• the Uba6 expression vector is a yeast expression vector.
• yeast expression vectors for expression in yeast S. cerevisiae include pYepSecl (Baldari et al., (1987) Embo J. 6:229), pMFa (Kurjan and Herskowitz, (1982) Cell 30:933), pJRY88 (Schultz et al., (1987) Gene 54:113), pYES2 (Invitrogen, San Diego, CA), and picZ (Invitrogen, San Diego, CA).
• Uba6 and/or E2Z polypeptides can be expressed in insect cells using baculovirus expression vectors.
• Baculovirus vectors available for expression of proteins in cultured insect cells include the pAc series (Smith et al. (1983) MoI. Cell Biol. 3:2156) and the pVL series (Lucklow and Summers (1989) Virology 170:31).
• a nucleic acid of the invention is expressed in mammalian cells using a mammalian expression vector.
• mammalian expression vectors include pCDM8 (Seed, B. (1987) Nature 329:840) and pMT2PC (Kaufman et al. (1987) EMBO J. 6:187).
• the expression vector's control functions are often provided by viral regulatory elements.
• commonly used promoters are derived from polyoma, adenovirus 2, cytomegalovirus and Simian virus 40.
• suitable expression systems for both prokaryotic and eukaryotic cells see chapters 16 and 17 of Sambrook, J., Fritsh, E. F., and Maniatis, T., Molecular Cloning: A Laboratory Manual, 2nd, ed., Cold Spring Harbor Laboratory, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N. Y., 1989.
• the recombinant mammalian expression vector is capable of directing expression of the nucleic acid preferentially in a particular cell type (e.g., tissue-specific regulatory elements are used to express the nucleic acid).
• tissue-specific regulatory elements are known in the art.
• suitable tissue-specific promoters include the albumin promoter (liver-specific; Pinkert et al. (1987) Genes Dev. 1 :268), lymphoid-specific promoters (Calame and Eaton (1988) Adv. Immunol. 43:235), in particular promoters of T cell receptors (Winoto and Baltimore (1989) EMBO J.
• the present invention provides a nucleic acid molecule which is antisense to a Uba6 nucleic acid molecule.
• antisense refers to a nucleic acid that interferes with the function of DNA and/or RNA and may result in suppression of expression of the RNA and/or DNA.
• the antisense nucleic acid comprises a nucleotide sequence which is complementary to a "sense" nucleic acid encoding a protein, e.g., complementary to the coding strand of a double-stranded cDNA molecule or complementary to an mRNA sequence. Accordingly, an antisense nucleic acid can hydrogen bond to a sense nucleic acid.
• the antisense nucleic acid can be complementary to an entire Uba6 coding strand, or to only a portion thereof.
• an antisense nucleic acid molecule can be delivered to a cell to express an exogenous nucleotide sequence, to inhibit, eliminate, augment, or alter expression of an endogenous nucleotide sequence, or to express a specific physiological characteristic not naturally associated with the cell.
• the antisense nucleic acid is an antisense RNA, an interfering double stranded RNA ("dsRNA”), a short interfering RNA (“siRNA”) or a ribozyme.
• siRNA refers to double-stranded RNA that is less than 30 bases, such as 21-25 bases in length.
• siRNA may be prepared by any method known in the art. For a review of siRNA and RNA interference, see Macrae et al. (2006) Science 311 :195; Vermeulen et al. (2005) RNA 11 :674; Nishikura (2001) Cell 16:415; Fire et al. (1998) Nature 391 :806.
• single-stranded, gene-specific sense and antisense RNA oligomers with overhanging 3' deoxynucleotides are prepared and purified.
• two oligomers can be annealed by heating to 94 0C for 2 minutes, cooling to 90 0 C for 1 minute, and then cooling to 20 0 C at a rate of 1 0 C per minute.
• the siRNA can then be injected into an animal or delivered into a desired cell type using methods of nucleic acid delivery described herein.
• Another aspect of the invention pertains to host cells into which a recombinant expression vector of the invention has been introduced, containing sequences which allow it to homologously recombine into a specific site of the host cell's genome.
• host cell and “recombinant host cell” are used interchangeably herein. It is understood that such terms refer not only to the particular subject cell but to the progeny or potential progeny of such a cell. Because certain modifications may occur in succeeding generations due to either mutation or environmental influences, such progeny may not, in fact, be identical to the parent cell, but are still included within the scope of the term as used herein.
• a host cell can be any prokaryotic or eukaryotic cell.
• host cells can be bacterial cells such as E. coli, insect cells (e.g., Drosophila cells), yeast, Xenopus cells, zebrafish cells, or mammalian cells (such as Chinese hamster ovary cells (CHO), African green monkey kidney cells (COS), or fetal human cells (293T)).
• suitable host cells are known to those skilled in the art.
• Vector DNA can be introduced into prokaryotic or eukaryotic cells via conventional transformation or transfection techniques.
• transformation and “transfection” are intended to refer to a variety of art-recognized techniques for introducing foreign nucleic acid (e.g., DNA) into a host cell, including calcium phosphate or calcium chloride co-precipitation, DEAE-dextran-mediated transfection, lipofection, or electroporation. Suitable methods for transforming or transfecting host cells can be found in Sambrook, et al. ⁇ Molecular Cloning: A Laboratory Manual, 2nd, ed., Cold Spring Harbor Laboratory, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1989), and other laboratory manuals.
• a gene that encodes a selectable marker (e.g., resistance to antibiotics) is generally introduced into the host cells along with the gene of interest.
• selectable markers include those which confer resistance to drugs, such as G418, hygromycin and methotrexate.
• Nucleic acid encoding a selectable marker can be introduced into a host cell on the same vector as that encoding a detectable translation product or can be introduced on a separate vector.
• a host cell of the invention such as a prokaryotic or eukaryotic host cell in culture, can be used to produce (i.e., express) a Uba6 and/or an E2Z protein or portion thereof. Accordingly, the invention further provides methods for producing a Uba6 and/or an E2Z protein or portion thereof using the host cells of the invention.
• the method comprises culturing the host cell of invention (into which a recombinant expression vector encoding a detectable translation product has been introduced) in a suitable medium such that a detectable translation product is produced.
• the method further comprises isolating a Uba6 and/or an E2Z protein or portion thereof from the medium or the host cell.
• the host cells of the invention can also be used to produce nonhuman transgenic animals.
• a host cell of the invention is a fertilized oocyte or an embryonic stem cell into which Uba6-coding sequences have been introduced. Such host cells can then be used to create non-human transgenic animals in which exogenous Uba6 sequences have been introduced into their genome.
• a "transgenic animal” is a non-human animal, such as a mammal (e.g., a rodent such as a rat or mouse), in which one or more of the cells of the animal includes a transgene.
• transgenic animals include non-human primates, sheep, dogs, cows, goats, chickens, amphibians, etc.
• a transgene is exogenous DNA which is integrated into the genome of a cell from which a transgenic animal develops and which remains in the genome of the mature animal, thereby directing the expression of an encoded gene product in one or more cell types or tissues of the transgenic animal.
• a "homologous recombinant animal” is a non-human animal such as a mamma (e.g., a mouse), in which an endogenous gene has been altered by homologous recombination between the endogenous gene and an exogenous DNA molecule introduced into a cell of the animal, e.g., an embryonic cell of the animal, prior to development of the animal.
• a mamma e.g., a mouse
• An exemplary method for detecting Uba6 and/or E2Z expression or Uba6 and/or E2Z activity in a biological sample involves obtaining a biological sample from a test subject and contacting the biological sample with a compound or an agent capable of detecting Uba6 and/or E2Z expression or Uba6 and/or E2Z activity (e.g., ubiquitin activation; ubiquitin-adenylate intermediate formation; ubiquitin thiol esterif ⁇ cation; ubiquitin transfer to one or more ubiquitin-conjugating enzymes (e.g., E2s); ubiquitin transfer to one or more ubiquitin-protein ligases (e.g., E3s); and/or ubiquitination of one or more target polypeptides).
• a compound or an agent capable of detecting Uba6 and/or E2Z expression or Uba6 and/or E2Z activity e.g., ubiquitin activation; ubiquit
• an agent for detecting Uba6 and/or E2Z expression or Uba6 and/or E2Z activity e.g., ubiquitin activation; ubiquitin-adenylate intermediate formation; ubiquitin thiol esterif ⁇ cation; ubiquitin transfer to one or more ubiquitin-conjugating enzymes (e.g., E2s); ubiquitin transfer to one or more ubiquitin-protein ligases (e.g., E3s); and/or ubiquitination of one or more target polypeptides) is an antibody capable of binding to Uba6, ubiquitin and/or a target polypeptide or protein, such as an antibody.
• Antibodies can be polyclonal or monoclonal. An intact antibody, or a fragment thereof (e.g., Fab or F(ab')2) can be used.
• the term "labeled,” with regard to the probe or antibody, is intended to encompass direct labeling of the probe or antibody by coupling (i.e., physically linking) a detectable substance to the probe or antibody, as well as indirect labeling of the probe or antibody by reactivity with another reagent that is directly labeled. Examples of indirect labeling include detection of a primary antibody using a fluorescently labeled secondary antibody and end-labeling of a DNA probe with biotin such that it can be detected with fluorescently labeled streptavidin.
• biological sample is intended to include tissues, cells and biological fluids isolated from a subject, as well as tissues, cells and fluids present within a subject. That is, the detection method of the invention can be used to detect Uba6 and/or E2Z expression or Uba6 and/or E2Z activity in a biological sample in vitro as well as in vivo.
• in vitro techniques for detection of Uba6 and/or E2Z include enzyme linked immunosorbent assays (ELISAs), Western blots, immunoprecipitations and immunofluorescence.
• in vivo techniques for detection of Uba6 and/or E2Z expression or Uba6 and/or E2Z activity include introducing into a subject a labeled anti-Uba ⁇ and/or an anti-E2Z antibody, a labeled anti-ubiquitin antibody, a labeled anti-E2 antibody, a labeled anti-E3 antibody, a labeled anti-target protein or the like.
• the antibody can be labeled with a radioactive marker whose presence and location in a subject can be detected by standard imaging techniques.
• the biological sample contains protein molecules from the test subject.
• a biological sample is a serum sample isolated by conventional means from a subject.
• the methods further involve obtaining a control biological sample from a control subject, contacting the control sample with a compound or agent capable of detecting Uba6 and/or E2Z expression or Uba6 and/or E2Z activity, such that the presence of Uba6 and/or E2Z expression or Uba6 and/or E2Z activity is detected in the biological sample, and comparing the presence of Uba6 and/or E2Z expression or Uba6 activity in the control sample with the presence of Uba6 and/or E2Z expression or Uba6 and/or E2Z activity in the test sample.
• kits for detecting the presence of Uba6 and/or E2Z expression or Uba6 and/or E2Z activity in a biological sample can comprise a labeled compound or agent capable of detecting Uba6 and/or E2Z expression or Uba6 and/or E2Z activity in a biological sample; means for determining the amount of Uba6 and/or E2Z expression or Uba6 and/or E2Z activity in the sample; and means for comparing the amount of Uba6 and/or E2Z expression or Uba6 and/or E2Z activity in the sample with a standard.
• the compound or agent can be packaged in a suitable container.
• the kit can further comprise instructions for using the kit to detect Uba6 and/or E2Z expression or Uba6 and/or E2Z activity.
• the diagnostic methods described herein can furthermore be utilized to identify subjects having or at risk of developing a disease or disorder associated with aberrant Uba6 expression or activity (e.g., cancer).
• a disease or disorder associated with aberrant Uba6 expression or activity e.g., cancer
• the assays described herein can be utilized to identify a subject having or at risk of developing a disorder associated with a misregulation in Uba6 expression and/or activity, such as ubiquitin-related disorders such as cancer, inflammatory disorders, neurodegenerative disorders and the like.
• the present invention provides a method for identifying a disease or disorder associated with aberrant Uba6 and/or E2Z expression or activity in which a test sample is obtained from a subject and Uba6 and/or E2Z expression and/or Uba6 and/or E2Z activity is detected, wherein the presence of Uba6 and/or E2Z expression and/or Uba6 and/or E2Z activity is diagnostic for a subject having or at risk of developing a disease or disorder associated with aberrant Uba6 and/or E2Z expression and/or Uba6 and/or E2Z activity expression or activity.
• a test sample refers to a biological sample obtained from a subject of interest.
• a test sample can be a biological fluid (e.g., serum), cell sample, or tissue.
• the prognostic assays described herein can be used to determine whether a subject can be administered an agent (e.g., an agonist, antagonist, peptidomimetic, protein, peptide, nucleic acid, small molecule, or other drug candidate) to treat a disease or disorder associated with aberrant Uba6 and/or E2Z expression or activity.
• an agent e.g., an agonist, antagonist, peptidomimetic, protein, peptide, nucleic acid, small molecule, or other drug candidate
• such methods can be used to determine whether a subject can be effectively treated with an agent for cancer.
• the present invention provides methods for determining whether a subject can be effectively treated with an agent for a disorder associated with aberrant Uba6 and/or E2Z expression or activity in which a test sample is obtained and Uba6 and/or E2Z expression and/or Uba6 and/or E2Z activity is detected.
• the methods of the invention can also be used to detect genetic alterations in a Uba6 and/or an E2Z gene, thereby determining if a subject with the altered gene is at risk for a disorder characterized by misregulation in Uba6 and/or E2Z activity, such as cancer.
• the methods include detecting, in a sample of cells from the subject, the presence or absence of a genetic alteration characterized by at least one of: an alteration affecting the integrity of a gene encoding a Uba6 and/or E2Z protein; the misexpression of the Uba6 and/or E2Z gene; or aberrant activity of the Uba6 and/or E2Z protein.
• such genetic alterations can be detected by ascertaining the existence of at least one of: 1) a deletion of one or more nucleotides from a Uba6 and/or an E2Z gene; 2) an addition of one or more nucleotides to a Uba6 and/or an E2Z gene; 3) a substitution of one or more nucleotides of a Uba6 and/or an E2Z gene, 4) a chromosomal rearrangement of a Uba6 and/or an E2Z gene; 5) an alteration in the level of a messenger RNA transcript of a Uba6 and/or an E2Z gene; 6) aberrant modification of a Uba6 and/or an E2Z gene, such as of the methylation pattern of the genomic DNA; 7) the presence of a non-wild type splicing pattern of a messenger RNA transcript of a Uba6 and/or an E2Z gene; 8) a non-wild type level of a Ub
• detection of the alteration involves the use of a probe/primer in a polymerase chain reaction (PCR) (see, e.g., U.S. Patent Nos. 4,683,195 and 4,683,202), such as anchor PCR or RACE PCR, or, alternatively, in a ligation chain reaction (LCR) (see, e.g., Landegran et al. (1988) Science 241 :1077; and Nakazawa et al. (1994) Proc. Natl. Acad. ScL USA 91 :360), the latter of which can be particularly useful for detecting point mutations in the Uba6 gene (see Abravaya et al.
• PCR polymerase chain reaction
• LCR ligation chain reaction
• This method can include the steps of collecting a sample of cells from a subject, isolating nucleic acid (e.g., genomic, mRNA or both) from the cells of the sample, contacting the nucleic acid sample with one or more primers which specifically hybridize to a Uba6 gene under conditions such that hybridization and amplification of the Uba6 gene (if present) occurs, and detecting the presence or absence of an amplification product, or detecting the size of the amplification product and comparing the length to a control sample. It is anticipated that PCR and/or LCR may be desirable to use as a preliminary amplification step in conjunction with any of the techniques used for detecting mutations described herein.
• nucleic acid e.g., genomic, mRNA or both
• Alternative amplification methods include: self sustained sequence replication (Guatelli et al. (1990) Proc. Natl. Acad. Sci. USA 87:1874), transcriptional amplification system (Kwoh et al. (1989) Proc. Natl. Acad. Sci. USA 86:1173), Q- Beta Replicase (Lizardi, P. M. et al. (1988) Biotechnology 6:1197), or any other nucleic acid amplification method, followed by the detection of the amplified molecules using techniques well known to those of skill in the art. These detection schemes are especially useful for the detection of nucleic acid molecules if such molecules are present in very low numbers.
• mutations in a Uba6 gene from a sample cell can be identified by alterations in restriction enzyme cleavage patterns.
• sample and control DNA is isolated, amplified (optionally), digested with one or more restriction endonucleases, and fragment length sizes are determined by gel electrophoresis and compared. Differences in fragment length sizes between sample and control DNA indicates mutations in the sample DNA.
• sequence specific ribozymes see, for example, U.S. Pat. No. 5,498,531 can be used to score for the presence of specific mutations by development or loss of a ribozyme cleavage site.
• genetic mutations in Uba6 can be identified by hybridizing a sample and control nucleic acids, e.g., DNA or RNA, to high density arrays containing hundreds or thousands of oligonucleotides probes (Cronin, M. T. et al. (1996) Human Mutation 7: 244; Kozal, M. J. et al. (1996) Nature Medicine 2:753).
• a sample and control nucleic acids e.g., DNA or RNA
• high density arrays containing hundreds or thousands of oligonucleotides probes e.g., DNA or RNA
• genetic mutations in Uba6 can be identified in two dimensional arrays containing light-generated DNA probes as described in Cronin et al., supra.
• a first hybridization array of probes can be used to scan through long stretches of DNA in a sample and control to identify base changes between the sequences by making linear arrays of sequential overlapping probes. This step allows the identification of point mutations. This step is followed by a second hybridization array that allows the characterization of specific mutations by using smaller, specialized probe arrays complementary to all variants or mutations detected.
• Each mutation array is composed of parallel probe sets, one complementary to the wild-type gene and the other complementary to the mutant gene.
• any of a variety of sequencing reactions known in the art can be used to directly sequence the Uba6 and/or E2Z gene and detect mutations by comparing the sequence of the sample Uba6 and/or E2Z with the corresponding wild- type (control) sequence.
• Examples of sequencing reactions include those based on techniques developed by Maxam and Gilbert ((1977) Proc. Natl. Acad. Sci. USA 74:560) or Sanger ((1977) Proc. Natl. Acad. Sci. USA 74:5463).
• any of a variety of automated sequencing procedures can be utilized when performing the diagnostic assays ((1995) Biotechniques 19:448), including sequencing by mass spectrometry (see, e.g., PCT International Publication No. WO 94/16101; Cohen et al. (1996) Adv. Chromatogr. 36:127-162; and Griffin et al. (1993) Appl. Biochem. Biotechnol. 38:147).
• RNA/RNA or RNA/DNA heteroduplexes Other methods for detecting mutations in the Uba6 and/or E2Z gene include methods in which protection from cleavage agents is used to detect mismatched bases in RNA/RNA or RNA/DNA heteroduplexes (Myers et al. (1985) Science 230:1242).
• the art technique of "mismatch cleavage" starts by providing heteroduplexes formed by hybridizing (labeled) RNA or DNA containing the wild-type Uba6 and/or E2Z sequence with potentially mutant RNA or DNA obtained from a tissue sample.
• RNA/DNA duplexes can be treated with RNase and DNA/DNA hybrids treated with Sl nuclease to enzymatically digesting the mismatched regions.
• either DNA/DNA or RNA/DNA duplexes can be treated with hydroxylamine or osmium tetroxide and with piperidine in order to digest mismatched regions. After digestion of the mismatched regions, the resulting material is then separated by size on denaturing polyacrylamide gels to determine the site of mutation. See, for example, Cotton et al.
• control DNA or RNA can be labeled for detection.
• the mismatch cleavage reaction employs one or more proteins that recognize mismatched base pairs in double-stranded DNA (so called "DNA mismatch repair" enzymes) in defined systems for detecting and mapping point mutations in Uba6 and/or E2Z cDNAs obtained from samples of cells.
• DNA mismatch repair enzymes
• the mutY enzyme of E. coli cleaves A at G/A mismatches and the thymidine DNA glycosylase from HeLa cells cleaves T at G/T mismatches (Hsu et al. (1994) Carcinogenesis 15:1657).
• a probe based on a Uba6 and/or an E2Z sequence e.g., a wild-type Uba6 and/or E2Z sequence
• a cDNA or other DNA product from a test cell(s).
• the duplex is treated with a DNA mismatch repair enzyme, and the cleavage products, if any, can be detected from electrophoresis protocols or the like. See, for example, U.S. Patent No. 5,459,039.
• alterations in electrophoretic mobility will be used to identify mutations in Uba6 and/or E2Z genes.
• SSCP single strand conformation polymorphism
• Single-stranded DNA fragments of sample and control Uba6 nucleic acids will be denatured and allowed to renature.
• the secondary structure of single-stranded nucleic acids varies according to sequence, the resulting alteration in electrophoretic mobility enables the detection of even a single base change.
• the DNA fragments may be labeled or detected with labeled probes.
• the sensitivity of the assay may be enhanced by using RNA (rather than DNA), in which the secondary structure is more sensitive to a change in sequence.
• the subject method utilizes heteroduplex analysis to separate double stranded heteroduplex molecules on the basis of changes in electrophoretic mobility (Keen et al. (1991) Trends Genet. 7:5).
• the movement of mutant or wild-type fragments in polyacrylamide gels containing a gradient of denaturant is assayed using denaturing gradient gel electrophoresis (DGGE) (Myers et al. (1985) Nature 313:495).
• DGGE denaturing gradient gel electrophoresis
• DNA will be modified to insure that it does not completely denature, for example by adding a GC clamp of approximately 40 bp of high-melting GC-rich DNA by PCR.
• a temperature gradient is used in place of a denaturing gradient to identify differences in the mobility of control and sample DNA (Rosenbaum and Reissner (1987) Biophys. Chem. 265:12753).
• oligonucleotide primers may be prepared in which the known mutation is placed centrally and then hybridized to target DNA under conditions which permit hybridization only if a perfect match is found (Saiki et al. (1986) Nature 324:163); Saiki et al. (1989) Proc. Natl Acad. Sci. USA 86:6230).
• Such allele specific oligonucleotides are hybridized to PCR amplified target DNA or a number of different mutations when the oligonucleotides are attached to the hybridizing membrane and hybridized with labeled target DNA.
• Oligonucleotides used as primers for specific amplification may carry the mutation of interest in the center of the molecule (so that amplification depends on differential hybridization) (Gibbs et al. (1989) Nucl. Acids Res. 17:2437) or at the extreme 3' end of one primer where, under appropriate conditions, mismatch can prevent, or reduce polymerase extension (Prossner (1993) Tibtech 11 :238).
• amplification may also be performed using Taq ligase for amplification (Barany (1991) Proc. Natl. Acad. Sci. USA 88:189). In such cases, ligation will occur only if there is a perfect match at the 3' end of the 5' sequence making it possible to detect the presence of a known mutation at a specific site by looking for the presence or absence of amplification.
• the methods described herein may be performed, for example, by utilizing prepackaged diagnostic kits comprising at least one probe nucleic acid or antibody reagent described herein, which may be conveniently used, e.g., in clinical settings to diagnose patients exhibiting symptoms or family history of a disease or illness involving a Uba6 gene. Furthermore, any cell type or tissue in which Uba6 is expressed may be utilized in the prognostic assays described herein.
• Uba6 and/or E2Z e.g., ubiquitin activation; ubiquitin-adenylate intermediate formation; ubiquitin thiol esterif ⁇ cation; ubiquitin transfer to one or more ubiquitin-conjugating enzymes (e.g., E2s); ubiquitin transfer to one or more ubiquitin- protein ligases (e.g., E3s); and/or ubiquitination of one or more target polypeptides (e.g., ubiquitin, an E2, an E3, a target polypeptide and/or protein or the like) can be applied not only in basic drug screening, but also in clinical trials.
• agents e.g., drugs
• Uba6 and/or E2Z e.g., ubiquitin activation; ubiquitin-adenylate intermediate formation; ubiquitin thiol esterif ⁇ cation; ubiquitin transfer to one or more ubiquitin-conjugating enzymes
• the effectiveness of an agent determined by a screening assay as described herein to increase Uba6 and/or E2Z gene expression or protein levels, or upregulate Uba6 and/or E2Z activity can be monitored in clinical trials of subjects exhibiting decreased Uba6 and/or E2Z gene expression, protein levels, or downregulated Uba6 and/or E2Z activity.
• the effectiveness of an agent determined by a screening assay to decrease Uba6 and/or E2Z gene expression, or protein levels, or downregulate or Uba6 and/or E2Z activity can be monitored in clinical trials of subjects exhibiting increased Uba6 and/or E2Z gene expression, protein levels, or upregulated Uba6 and/or E2Z activity.
• the present invention provides a method for monitoring the effectiveness of treatment of a subject with an agent (e.g., an agonist, antagonist, peptidomimetic, protein, peptide, nucleic acid, small molecule, or other drug candidate identified by the screening assays described herein) including the steps of (i) obtaining a pre-administration sample from a subject prior to administration of the agent; (ii) detecting the level of expression of a Uba6 and/or an E2Z protein, mRNA, or genomic DNA or of the level of Uba6 and/or E2Z activity in the preadministration sample; (iii) obtaining one or more post-administration samples from the subject; (iv) detecting the level of expression or activity of the Uba6 and/or E2Z protein, mRNA, or genomic DNA or of the level of Uba6 and/or E2Z activity in the post- administration samples; (v) comparing the level of expression or activity of the Uba6 and/or E
• an agent e.g.
• increased administration of the agent may be desirable to increase the expression or activity of Uba6 and/or E2Z to higher levels than detected, i.e., to increase the effectiveness of the agent.
• decreased administration of the agent may be desirable to decrease expression or activity of Uba6 to lower levels than detected, i.e. to decrease the effectiveness of the agent.
• Uba6 and/or E2Z expression or activity may be used as an indicator of the effectiveness of an agent, even in the absence of an observable phenotypic response.
• a Novel Vertebrate El Protein, Uba6 Promotes Activation of
• the El for ubiquitin is a member of a family of proteins that contains a protein fold, the ThiF domain, found in ancient metabolic enzymes in bacteria (Lake et al. (2001) Nature 414:325). Using this domain to identify related proteins bioinformatically, a previously uncharacterized protein was identified with similarity to Ubel, the canonical El activating enzyme for ubiquitin (GenBank Accession FLJ10808), Uba6. Uba6 orthologs exist in mouse, rat, and zebrafish (Dr), but are not found in non- vertebrate metazoans or in yeast (Figure IA). Phylogenetically, Uba6 is more distantly related to Ubel than is UbelL ( Figure IG).
• cysteine to serine mutant was expected to support formation of an ester linked ubiquitin or ubiquitin like protein which is more stable that the thiol ester formed with cysteine.
• previous studies ( Komatsu et al. (2004) Embo J. 23:1977) have demonstrated that in certain cases, more stable conjugates can be formed with ester linkages than with thiol ester linkages.
• Flag-HA-Uba6 Flag-HA- Uba6 and Flag-HA-Uba6 were expressed at near endogenous levels from a lentiviral vector driven by the PGK promoter. Again, the C625S mutant, but not WT or C625A proteins, expressed a more slowly migrating protein consistent with ubiquitination (Figure 2B). Taken together, these data indicate that Uba6 functions to activate ubiquitin in tissue culture cells.
• Uba6 Promotes Transfer of Ubiquitin to E2s with Specificity Distinct from Ubel
• Ubel promotes the transfer of ubiquitin from its active site cysteine residue to the active site cysteine of an E2 ubiquitin conjugating enzyme.
• a subset of E2s are known to be activated by Ubel, although a small number of E2s are specific for transfer to ubiquitin-like proteins (E2M/Ubcl2 is charged by Nedd8, E2I/Ubc9 is charged by SUMO, and E2L/Ubc8 is charged by ISG 15).
• E2M/Ubcl2 is charged by Nedd8
• E2I/Ubc9 is charged by SUMO
• E2L/Ubc8 is charged by ISG 15.
• An in vivo charging assay coupled with RNAi was used to deplete either Uba6 or Ubel.
• cell lysates were generated using buffers at pH -4.5 [50 mM MES, pH 4.5, 0.5% NP40, 100 mM NaCl] and immediately subjected to non-reducing SDS-PAGE. Under these conditions, the E2 thiol esters remained relatively stable, allowing their separation by SDS-PAGE. Charged and uncharged E2s were then detected by immunoblot. Because antibodies against E2Z were not available, a cell line that stably expresses a Flag-HA-tagged version of E2Z was generated.
• mouse Ubely protein is -90% identical to mouse Ubelx and these proteins are located on the same clad of the El dendogram ( Figure 20).
• mouse Ubely is more closely related to mouse Ubelx and the corresponding human Ubel protein than is the zebraf ⁇ sh Ubel protein ( Figure 20).
• UBEl related sequences on rat chromosome-Y but these sequences do not appear to constitute a complete UBEl gene (see GenBank ID 25225).
• Multiple Ubel orthologs exist in plants (for example, 2 genes in Arabidopsis (Hatfield et al. (1997) Plant J. 11 :213) and three genes in wheat, Figure 20).
• Models of these proteins were built based on the structures of related proteins: the Ufd from SUMOl (pdb code:lY8Q) for Uba6 and Ubel, UbcHl (ITTE) in the case of Cdc34A, and UbcH5B (2ESQ) in the case of Usel.
• Ufds and Cdc34 were generated using Modeller while models for Usel were generated using Swissmodel.
• the N-terminal helix (Helix 1) of Ubcl2 makes several contacts with the surface of a ⁇ -sheet in the Ufd composed primarily of S2, S3, and S4 ( Figure 21B).
• the surface of the Ufd ⁇ -sheet facing the Ubcl2 helix is composed primarily of residues with small and/or hydrophilic side chains (A380, T382, T384, T391, A424, A426) ( Figures 21A and 21B). This facilitates interaction
• the Uba3 has an acidic patch (red) not seen in the Ufds from Uba6 or Ubel.
• the Hl helix of Usel is much more hydrophobic in character, consistent with
• open reading frames were cloned into pENTR/TOPO (Invitrogen, Carlsbad, CA) and transferred into the appropriate expression plasmid using in vitro recombination with Clonase (Invitrogen).
• the pHAGE-Flag-HA vector puromycin resistant places the open reading frame under control of the PGK promoter.
• Open reading frames for E2s were placed into vectors containing T7 promoters and an N-terminal His-6 tag.
• the Usel open reading frame (NM 023079) was cloned into pENTR-2 containing a TEV protease cleavage site upstream of the open reading frame and transferred into pDEST-15 (N-terminal GST tag from Invitrogen).
• the annotated open reading frame for Usel (referred to as UBE2Z) (Gu, X. et al. Cloning and characterization of a gene encoding the human putative ubiquitin conjugating enzyme E2Z (UBE2Z). MoI Biol Rep (2006)) is incorrect, as determined by the size of the endogenous protein detected using anti-Use 1 antibodies and by DNA sequence analysis.
• the actual open reading frame initiates 109 amino acids prior to the annotated start site ( Figure 20B). The sequences of all the genes examined are collected in Figure 22.
• Trees and alignments were generated using ClustalW in conjunction with Treeview.
• Uba6 and Usel antibodies were generated in rabbits using a GST-Uba6 fusion protein (residues 869-1052) and GST-Use 1, respectively, made in bacteria. Antibodies were affinity purified prior to use. The specificity of antibodies was determined by RNAi against Uba6 Usel .
• recombinant baculoviruses were used to infect Sf9 cells (40 h) and cleared cell extracts in lysis buffer (50 mM Tris-HCl, pH 7.5, 0.5 mM DTT, 150 mM NaCl, 0.5% Nonidet-P40, protease inhibitors (Roche)) were bound to anti-Flag or GSH-Sepharose beads.
• Washed beads were eluted with Flag peptide (500 ⁇ g/ml) or with glutathione (40 mM) and the protein dialyzed against 50 mM Tris-HCl, pH 7.5, 0.5 mM DTT, 150 mM NaCl, 50% glycerol. Bacterial expression was performed in Rosetta/DE3 cells using 0.4 mM IPTG induction for 3 h at 37 0 C. Cells were disrupted in lysis buffer prior to purification using GSH-Sepharose. All GST-UBL proteins were found to contain the appropriate C-termini by mass spectrometry.
• samples were treated with 200 mM DTT prior to electrophoresis in order to reduce thioester bonds.
• Gels were transferred to PVDF and probed with the indicated antibodies or, in some cases, bands were excised and subjected to mass spectrometry as described below.
• Ubel was released from GST-TEV-Usel using TEV protease and the eluted Usel dialyzed against 50 mM Tris-HCl, pH 7.5, 0.5 mM DTT, 150 mM NaCl, 50% glycerol.
• Capture of Uba6 and Ubel using ubiquitin-Sepharose was performed as described previously (Pickart et al. (1985) J. Biol Chem. 260:1573; Ciechanover et al. (1982) J. Biol. Chem. 257:2537) using extracts from cells stably expressing Flag-HA-Uba6. Mass Spectroscopy
• mass spectrometry was performed on peptides produced by in-gel trypsinization using a Thermo-Electron LTQ mass spectrometer. Searches were performed using Sequest. For determination of C-termini in GST-UBL fusion proteins, 2 ⁇ g of protein was excised from SDS-PAGE gels and digested with the protease indicated. Digested peptides were then subjected to LC/MS/MS under conditions where >3250 MS/MS scans were obtained for each LC/MS/MS run. The predicted C-terminal peptides as well as XCorr and dCn scores for the match with the predicted spectra.
• recombinant baculoviruses were used to infect Sf9 cells (40 hours) and cleared cell extracts in lysis buffer (50 mM Tris-HCl, pH 7.5, 0.5 mM DTT, 150 mM NaCl, 0.5% Nonidet-P40, protease inhibitors (Roche)) were bound to anti-Flag or GSH-Sepharose beads.
• Washed beads were eluted with Flag peptide (500 ⁇ g/ml) or with glutathione (40 mM) and the protein dialyzed against 50 mM Tris-HCl, pH 7.5, 0.5 mM DTT, 150 mM NaCl, 50% glycerol. Bacterial expression was performed in Rosetta/DE3 cells using 0.4 mM IPTG induction for 3 h at 37 0 C. Cells were disrupted in lysis buffer prior to purification using GSH-Sepharose. All GST-UBL proteins were found to contain the appropriate C-termini by mass spectrometry.
• samples were treated with 200 mM DTT prior to electrophoresis in order to reduce thioester bonds.
• Gels were transferred to PVDF and probed with the indicated antibodies or, in some cases, bands were excised and subjected to mass spectrometry as described below.
• Tissue culture cells were grown in Dulbecco's Modified Eagle Medium at 37 0 C in 5% CO 2 .
• the Uba6 ORFs were recombined into either pHAGE-CMV-Flag-HA-GAW or pHAGE-PGK-Flag-HA-GAW and viruses were packaged using standard lentivirus packaging procedures.
• Viral supernatants were used to infect 293 T cells at a multiplicity of infection of approximately 0.5. Cells were selected for integration using puromycin. Expression of Proteins in E. Coli
• BL21/DE3 cells (Novagen, Madison, WI) were transformed with the appropriate expression plasmid (pDEST-27, Invitrogen) and plasmids selected using carbocyclin. Cells were grown to 0.8 OD and induced with 0.4 mM IPTG. After three hours, cells were harvested, lysed in 50 mM Tris-HCl (pH 7.5), 150 mM NaCl, 1 mM EDTA, 0.5% NP40, and subjected to centrifugation at 12,000 g. Extracts were subjected to purification using GSH-Sepharose (Pharmacia, Piscataway, NJ).
• ORF clones were recombined with baculoviral sequences using Bac-N-Blue (Invitrogen) via co-transfection of Sf9 cells and viral supernatants isolated three days after transfection. Viral stocks were amplified in Sf9 cells.
• Sf9 cells were infected with viral stocks and cells were lysed after 40 hours using 50 mM Tris-HCl (pH 7.5), 150 mM NaCl, 1 mM EDTA, and 0.5% NP40 in the presence of proteasome inhibitors (Roche, Basel, Switzerland). Extracts were cleared by centrifugation and lysates were incubated with either anti- Flag (Sigma, St.
• Ubel or Uba6 100 ng was incubated in 50 mM Tris-HCl, pH 7.5, 50 mM NaCl, and 4 mM ATP for the time indicated above in the presence of 10 ⁇ g ubiquitin or ubiquitin-like protein (final volume of 10 ⁇ l). Reaction mixtures were subjected to non-reducing SDS-PAGE at the indicated times. Gels were either stained with Coomassie or subjected to immunob lotting with the antibodies indicated above.
• Ubiquitin activation assays contained 8 nM El, 100 nM GST-UBL and 2 mM ATP in 50 mM Tris-HCl, 5 mM KCl, 5 mM MgCh for 15 min at 30 ° C (total volume 10 ⁇ l). Reactions were quenched with 2X Laemli sample buffer lacking reducing agent, and subjected to non-reducing 4-12% Tris-glycine gel and immunob lotting. To examine E2 charging, the indicated E2 was in vitro translated using a bacterial S30 extract (Promega, Madison, WI) in the presence of 35 S-methionine.
• E2 (1 ⁇ l) was incubated with 40 nM El, 25 ⁇ M KO ubiquitin (Boston Biochem, Waltham, MA), 2 mM ATP (15 min, 30 C) (10 ⁇ l total volume) before 4-12% Tris-glycine gel/autoradiography.
• cell extracts were generated in pH 7.5 lysis buffer [50 mM Tris-HCl, pH 7.5, 150 mM NaCl, 0.5% Nonidet-P40, protease inhibitors (Roche, Indianapolis, IN)] or pH 4.5 lysis buffer (50 mM MES, pH 4.5, 150 mM NaCl, 0.2% Nonidet-P40, protease inhibitors). Proteins were separated on non-reducing 4-12% Tris-glycine or 4-12% Bis-Tris gradient gels prior to blotting or mass spectrometry.
• siRNA sequences siUba6-l, CCTTGGAAGAGAAGCCTGATGTAAA; siUba6-2, AC ACTGAAGTTATTG TACCGCATTT; siUba6-3, GGGATCGATGGACCGTACATGGAAA; siUbel-1,

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