{"gene":"UBE2M","run_date":"2026-06-10T10:51:56","timeline":{"discoveries":[{"year":2005,"finding":"Crystal structure of the complex between the C-terminal domain of NEDD8's E1 (APPBP1-UBA3) and the catalytic core domain of Ubc12 (UBE2M) reveals molecular details of Ubc12 recruitment by NEDD8's E1. The E1's Ubc12-binding domain resembles ubiquitin and recruits Ubc12 in a manner mimicking ubiquitin's interactions with ubiquitin-binding domains. Structural comparison with E2-E3 complexes indicates that the E1 and E3 binding sites on Ubc12 may overlap.","method":"X-ray crystallography of E1-E2 complex combined with mutational analysis","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1 / Strong — crystal structure determination with supporting mutational analyses in a focused mechanistic study","pmids":["15694336"],"is_preprint":false},{"year":2000,"finding":"UBC12 (UBE2M) is the E2 conjugating enzyme for NEDD8. The catalytic cysteine C111 is essential for NEDD8 transfer; the C111S point mutant forms a stable heterodimeric conjugate with NEDD8 (resistant to 6M guanidine HCl, urea, SDS, and β-mercaptoethanol), sequesters NEDD8, and acts as a dominant-negative inhibitor of NEDD8 conjugation to cullins (Cul-1, Cul-2) and other substrates. Overexpression of the dominant-negative mutant inhibits growth of U2OS and HEK293 cells.","method":"Active-site mutagenesis (C111S), dominant-negative overexpression, in vivo NEDD8 conjugation assays, cell growth assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — active-site mutagenesis with biochemical validation and cell-growth functional readout in a focused study","pmids":["10828074"],"is_preprint":false},{"year":2018,"finding":"UBE2M functions as a dual E2 enzyme: under physiological conditions it acts as a neddylation E2 to activate CUL3-Keap1 E3; under stress conditions (induced by HIF-1 and AP1 transactivation) it switches to a ubiquitylation E2 that, together with Parkin-DJ-1 E3, mediates targeted ubiquitylation and proteasomal degradation of the other neddylation E2, UBE2F. UBE2M-induced UBE2F degradation inactivates CRL5 and causes NOXA accumulation, suppressing lung cancer cell growth.","method":"Co-IP, siRNA knockdown, overexpression, ubiquitylation and neddylation assays, mass spectrometry, cell viability assays","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP plus in vitro ubiquitylation/neddylation assays and multiple functional readouts in a single focused study","pmids":["29932898"],"is_preprint":false},{"year":2017,"finding":"The DCN1-UBC12 protein-protein interaction is required for cellular neddylation of cullin 3 specifically; small-molecule inhibitor DI-591 (Ki ~10–12 nM for DCN1/DCN2) disrupts this interaction and selectively converts cullin 3 to an un-neddylated inactive form with minimal effect on other cullins, establishing a specific role of the DCN1-UBC12 interaction in CUL3 neddylation.","method":"Biochemical binding assays (Ki determination), cell-based co-immunoprecipitation, western blotting for cullin neddylation, small-molecule inhibitor DI-591","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — biochemical binding assays combined with cellular neddylation profiling, independently consistent with multiple inhibitor studies","pmids":["29074978"],"is_preprint":false},{"year":2018,"finding":"A UBC12 N-terminal peptide (12 residues) mediates high-affinity binding to the co-E3 DCN1; peptidomimetic inhibitors based on this peptide bind DCN1 with KD < 10 nM. Co-crystal structure of a potent peptidomimetic with DCN1 provides the structural basis for the DCN1-UBC12 interaction interface. Cellular inhibition selectively blocks cullin 3 neddylation.","method":"Co-crystal structure determination, surface plasmon resonance/ITC binding assays, cellular neddylation assays","journal":"Journal of medicinal chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — co-crystal structure with functional cellular validation, single lab but multiple orthogonal methods","pmids":["29438612"],"is_preprint":false},{"year":2014,"finding":"UBE2M is required for DNA damage repair and genome integrity. UBE2M knockdown increases DNA breaks, sensitizes cells to DNA damaging agents, and impairs RAD51 foci formation (homologous recombination). The downstream mechanism involves activation of Cullin 1, 2, and 4 ligases; specifically, loss of CUL2 neddylation blocks G1-to-S progression and delays S-phase DNA damage response, while loss of CUL4 neddylation causes elevated DNA breakages. Key CRL substrates CDT1, p21, and Claspin accumulate upon UBE2M knockdown and contribute to the elevated DNA damage phenotype.","method":"siRNA knockdown, RAD51 foci formation assay, cell-based DNA repair assays, flow cytometry (cell cycle), immunofluorescence","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal cell-based assays (RAD51 foci, DNA repair, cell cycle), single lab","pmids":["25025768"],"is_preprint":false},{"year":2023,"finding":"UBE2M mediates neddylation of E3 ubiquitin ligase TRIM21 at K129/134. This neddylation promotes TRIM21-dependent recruitment and ubiquitination-mediated degradation of the E3 ligase VHL. VHL loss stabilizes HIF-1α, increasing IL-1β production in macrophages, driving obesity-related inflammation.","method":"Macrophage-specific UBE2M knockout mice, co-IP, neddylation site mutagenesis (K129/134), western blotting, cytokine measurement, metabolic phenotyping","journal":"Cell metabolism","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo knockout model combined with site-specific mutagenesis and multiple orthogonal mechanistic assays","pmids":["37343564"],"is_preprint":false},{"year":2023,"finding":"UBE2M inhibits RIG-I degradation in macrophages by preventing the interaction of RIG-I with the E3 ligase STUB1, thereby sustaining antiviral IFN-I signaling. Conversely, IFN-I-activated STAT1 transcriptionally upregulates TRIM21, which promotes UBE2M degradation, forming a negative feedback loop. TRIM21 acts as an E3 to degrade UBE2M.","method":"UBE2M-deficient macrophages, RNA-virus infection models, Co-IP, siRNA knockdown, reporter and protein stability assays","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP plus UBE2M-deficient macrophage model, multiple mechanistic readouts, single lab","pmids":["36662617"],"is_preprint":false},{"year":2022,"finding":"Treg cell-specific deletion of Ube2m (neddylation E2) in mice causes disrupted Treg cell homeostasis and suppressive functions with an inflammatory disorder phenotype, demonstrating that the Ube2m-Rbx1 neddylation axis is specifically required for intrinsic regulatory processes in Treg cells. The phenotype is similar to but less severe than Rbx1 deletion, suggesting Rbx1 also has Ube2m-independent roles.","method":"Conditional knockout mice (Treg-specific Ube2m deletion), flow cytometry, immunophenotyping, inflammatory disease assessment","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo conditional knockout with rigorous immunophenotyping and genetic epistasis (Ube2m vs Rbx1 vs Ube2f deletions compared)","pmids":["35641500"],"is_preprint":false},{"year":2019,"finding":"UBC12/UBE2M knockdown in lung cancer cells inhibits cullin neddylation, inactivates CRL E3 ligases, and causes accumulation of tumor-suppressive CRL substrates p21, p27, and Wee1, triggering G2-phase cell-cycle arrest and suppressing malignant phenotypes in vitro and in vivo. UBC12 knockdown also inhibits growth of MLN4924-resistant lung cancer cells.","method":"siRNA knockdown, quantitative proteomics, flow cytometry (cell cycle), western blotting, xenograft mouse model","journal":"EBioMedicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (proteomics, FACS, in vivo xenograft), single lab","pmids":["31208947"],"is_preprint":false},{"year":2011,"finding":"UBE2M mediates gemcitabine-induced degradation of p27(Kip1) protein in human urothelial carcinoma cells. Gemcitabine induces UBE2M expression via a PI3K-dependent pathway; silencing UBE2M with siRNA restores p27(Kip1) levels and reduces gemcitabine sensitivity, establishing UBE2M as a mediator of drug cytotoxicity through p27(Kip1) degradation.","method":"2D gel electrophoresis, siRNA knockdown, proteasome inhibitor (MG132), PI3K inhibitor (LY294002), western blotting, cell sensitivity assays","journal":"Biochemical pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological and siRNA approaches with multiple mechanistic readouts, single lab","pmids":["21477582"],"is_preprint":false},{"year":2021,"finding":"UBE2M physically binds to MDM2 and to ribosomal protein L11 (but not directly to p53) in HCC cells, as shown by co-IP and immunofluorescence colocalization. UBE2M depletion activates p53 expression and stability; conversely, ectopic UBE2M enhances MDM2-mediated degradation of exogenous p53. L11 is required for p53 activation upon UBE2M depletion.","method":"Co-immunoprecipitation, immunofluorescence colocalization, overexpression/knockdown, western blotting, xenograft mouse model","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP and colocalization with functional rescue experiments, single lab, no reciprocal IP reported","pmids":["34638383"],"is_preprint":false},{"year":2021,"finding":"NPRL2 physically interacts with UBE2M (validated by Co-IP and immunofluorescence), and this interaction increases NPRL2 protein stability by reducing its polyubiquitination and proteasomal degradation. NPRL2 cooperatively enhances UBE2M-mediated neddylation and CRL substrate degradation.","method":"Co-immunoprecipitation, immunofluorescence, ubiquitination assays, siRNA knockdown, in vivo xenograft","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP validated with IF and functional assays, single lab","pmids":["33905671"],"is_preprint":false},{"year":2025,"finding":"PINK1 interacts with UBC12 (UBE2M) in the primate brain; knockdown of PINK1 in monkeys (but not in PINK1-knockout mice or pigs) markedly reduces UBC12 protein abundance and global neddylation levels, revealing a primate-specific PINK1-UBC12 axis regulating protein neddylation.","method":"Mass spectrometry proteomics, PINK1 knockdown in monkeys, colocalization imaging, western blotting for neddylation","journal":"Zoological research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — MS-based identification of interaction with in vivo primate knockdown validation and cross-species comparison","pmids":["41298302"],"is_preprint":false},{"year":2025,"finding":"UBE2M neddylates MKK7 (mitogen-activated protein kinase kinase 7) as a direct substrate. Neddylation of MKK7 inhibits its ubiquitination and proteasomal degradation, stabilizing MKK7 and enhancing its phosphorylation. Stabilized MKK7 activates JNK signaling, induces EGR1, and suppresses CCND2 expression to restrain melanoma cell proliferation.","method":"Co-IP, proximity ligation assay, cycloheximide chase assay, transcriptomic analysis, in vitro and in vivo functional assays","journal":"Journal of translational medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct neddylation substrate identification with multiple orthogonal methods (Co-IP, PLA, CHX chase), single lab","pmids":["41361309"],"is_preprint":false},{"year":2025,"finding":"PRMT1 methylates UBE2M at arginine R169, enhancing its protein function. This UBE2M post-translational modification increases neddylation and protein stability of NEDD4, which in turn ubiquitinates PPARγ for degradation, inhibiting fatty acid metabolism in renal tubular cells during calcium oxalate crystal-induced injury.","method":"Conditional PRMT1 knockout/overexpression mice, immunoprecipitation, mass spectrometry, GST-pulldown, site-specific mutagenesis (R169), single-cell RNA-seq, metabolomics","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — site-specific mutagenesis with in vivo mouse model and multiple orthogonal biochemical methods, single lab","pmids":["40744915"],"is_preprint":false},{"year":2026,"finding":"NAE1/UBA3 and UBE2M serve as the E1 and E2 enzymes, respectively, for URM1 (ubiquitin-related modifier 1) protein modification (urmylation) in human cells under normal and oxidative stress conditions. Pharmacological inhibition of the UBE2M-DCN1 module suggests DCN1 may contribute to URM1 conjugation.","method":"Activity-based URM1 probe to covalently capture cysteine enzymes, proteomic characterization, cell-based validation, pharmacological inhibition (pevonedistat)","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — activity-based probe with proteomic and cell-based validation, single study","pmids":["42056084"],"is_preprint":false},{"year":2026,"finding":"UBE2M neddylates NAA10 (N-alpha-acetyltransferase 10) as a direct substrate at lysine K148, with RBX1-CUL4A acting as the critical E3 ligase for this modification. UBE2M-mediated neddylation of NAA10 enhances its protein stability and functional activity, promoting prostate cancer cell proliferation.","method":"Co-immunoprecipitation, mass spectrometry, proximity ligation assay, neddylation site mutagenesis (K148), in vitro and in vivo functional assays","journal":"Journal of translational medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — site-specific neddylation site identified with MS and PLA, single lab","pmids":["41857595"],"is_preprint":false},{"year":2026,"finding":"UBE2M directly neddylates VEGFR2 in pulmonary endothelial cells, stabilizing the receptor. UBE2M deficiency in mice reduces VEGFR2 protein levels and phosphorylation, causing premature pulmonary vascular aging and structural disruption, while UBE2M reconstitution alleviates cellular senescence in a doxorubicin-induced model.","method":"Ube2m conditional knockout mice, neddylation assay, western blotting, immunofluorescence, doxorubicin senescence model, in vivo emphysema model","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo knockout model with biochemical neddylation assays and reconstitution, single lab","pmids":["42209461"],"is_preprint":false},{"year":2026,"finding":"UBE2M neddylates USP39, which in turn modulates deubiquitination of PABPC1, enhancing translation efficiency of CCNB1 and promoting G2/M cell cycle progression in colorectal cancer cells.","method":"Co-IP, in vivo and in vitro functional experiments, single-cell and bulk transcriptomics, protein stability assays","journal":"Experimental & molecular medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — novel neddylation substrate (USP39) identified with Co-IP and functional pathway validation, single lab","pmids":["41680469"],"is_preprint":false},{"year":2026,"finding":"UBE2M neddylates EGFR in keratinocytes, stabilizing and activating EGFR signaling. UBE2M is upregulated in psoriatic lesions and promotes keratinocyte proliferation and inflammatory responses through EGFR neddylation; genetic and pharmacological inhibition of UBE2M suppresses psoriasis-like development.","method":"Immunofluorescence in human and murine psoriasis lesions, UBE2M knockdown/overexpression, neddylation assays, IMQ-induced murine psoriasis model","journal":"iScience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct neddylation substrate (EGFR) identified with in vivo disease model validation, single lab","pmids":["42111190"],"is_preprint":false},{"year":2026,"finding":"Orlistat directly binds UBC12 (UBE2M) with a KD of 678 nM (ITC assay), inhibits UBC12's NEDD8-conjugating activity, and blocks UBC12's interaction with DCN1, selectively suppressing cullin 1 neddylation. UBC12 overexpression positively regulates Wnt/β-catenin signaling, and UBC12 depletion abrogates Orlistat's inhibition of Wnt signaling.","method":"Isothermal titration calorimetry (ITC), neddylation activity assays, co-immunoprecipitation, western blotting, overexpression/knockdown","journal":"Pharmacological research","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — direct binding measured by ITC plus functional neddylation assays, single lab","pmids":["42067003"],"is_preprint":false},{"year":2024,"finding":"UBE2M maintains ERα expression by inhibiting its ubiquitination and degradation through a UBE2M-CUL3/4A-E6AP-ERα axis in ER-positive breast cancer. ERα in turn enhances HIF-1α-mediated transcription of UBE2M, forming a positive feedback loop. Silencing UBE2M suppresses growth and sensitizes cells to fulvestrant in vitro and in vivo.","method":"siRNA knockdown, overexpression, ubiquitination assays, co-IP, western blotting, xenograft mouse model","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ubiquitination assays with Co-IP and in vivo validation, single lab","pmids":["39138151"],"is_preprint":false}],"current_model":"UBE2M (hUbc12/UBC12) is the primary E2 NEDD8-conjugating enzyme that accepts activated NEDD8 from the E1 (NAE1/UBA3) via its catalytic cysteine (C111) and transfers NEDD8 to substrate proteins, most prominently cullin family members (CUL1–5) to activate Cullin-RING E3 ligases (CRLs); the co-E3 DCN1 binds the UBE2M N-terminus to specifically enhance CUL1 and CUL3 neddylation; UBE2M can also act as a ubiquitylation E2 (e.g., for UBE2F degradation via Parkin-DJ-1 under stress), neddylates non-cullin substrates including TRIM21, MKK7, EGFR, VEGFR2, NAA10, USP39, and is itself regulated by PRMT1-mediated arginine methylation at R169, TRIM21-mediated ubiquitination (negative feedback downstream of STAT1/IFN-I), and a primate-specific interaction with PINK1 that stabilizes UBE2M protein."},"narrative":{"mechanistic_narrative":"UBE2M (hUbc12/UBC12) is the primary E2 NEDD8-conjugating enzyme that drives neddylation of cullin-RING E3 ligases, coupling protein modification to cell-cycle, DNA-repair, immune, and metabolic programs [PMID:10828074, PMID:25025768]. It is charged with activated NEDD8 by the NEDD8 E1 (APPBP1-UBA3), which recruits UBE2M through a ubiquitin-like binding domain that engages the E2 catalytic core in a manner overlapping the E3-binding surface, and transfer to substrates requires the essential active-site cysteine C111 [PMID:15694336, PMID:10828074]. Substrate specificity is sharpened by the co-E3 DCN1, which binds a 12-residue N-terminal UBE2M peptide; this interaction is selectively required for neddylation of cullin 3 (and cullin 1), and disrupting it with peptidomimetic or small-molecule inhibitors converts these cullins to inactive un-neddylated forms [PMID:29074978, PMID:29438612, PMID:42067003]. Through cullin neddylation UBE2M activates CRLs that turn over key substrates including CDT1, p21, p27, Wee1, and Claspin, so its loss stabilizes these factors, blocks cell-cycle progression, impairs RAD51-dependent homologous recombination, and elevates DNA damage [PMID:25025768, PMID:31208947]. Beyond cullins, UBE2M directly neddylates a growing set of non-cullin substrates — TRIM21, MKK7, EGFR, VEGFR2, NAA10, and USP39 — typically stabilizing them by antagonizing their ubiquitin-mediated degradation, thereby tuning inflammatory, MAPK/JNK, receptor-tyrosine-kinase, and translation pathways [PMID:37343564, PMID:41361309, PMID:41857595, PMID:42209461, PMID:41680469, PMID:42111190]. UBE2M can also act as a ubiquitylation E2: under stress it partners with Parkin-DJ-1 to degrade the sister neddylation E2 UBE2F, inactivating CRL5 [PMID:29932898]. Its own activity and abundance are controlled by PRMT1-mediated arginine methylation at R169, by TRIM21-mediated ubiquitination in a STAT1/IFN-I negative-feedback loop, and by a primate-specific PINK1 interaction that sustains UBE2M protein levels [PMID:36662617, PMID:41298302, PMID:40744915].","teleology":[{"year":2000,"claim":"Established UBE2M as the dedicated E2 for NEDD8 and pinpointed the catalytic residue, answering how NEDD8 is transferred to cullins.","evidence":"Active-site C111S mutagenesis, dominant-negative overexpression, and in vivo NEDD8 conjugation assays in U2OS/HEK293 cells","pmids":["10828074"],"confidence":"High","gaps":["Did not define the E1 or E3 interaction interfaces","Substrate range beyond Cul-1/Cul-2 not mapped"]},{"year":2005,"claim":"Resolved how the NEDD8 E1 recruits UBE2M, showing the E1 uses a ubiquitin-like domain to engage the E2 and that E1- and E3-binding sites may overlap.","evidence":"X-ray crystallography of the APPBP1-UBA3 / Ubc12 complex with mutational analysis","pmids":["15694336"],"confidence":"High","gaps":["Static structure does not capture the thioester transfer step","Does not address DCN1-dependent specificity"]},{"year":2011,"claim":"Linked UBE2M to drug cytotoxicity by showing it mediates degradation of the CDK inhibitor p27(Kip1), connecting neddylation to chemotherapy response.","evidence":"2D gel electrophoresis, siRNA knockdown, PI3K and proteasome inhibitors in urothelial carcinoma cells","pmids":["21477582"],"confidence":"Medium","gaps":["Did not establish which CRL mediates p27 turnover","Single cell-type context"]},{"year":2014,"claim":"Defined a genome-integrity role, showing UBE2M-dependent neddylation of CUL2 and CUL4 controls cell-cycle progression and DNA repair.","evidence":"siRNA knockdown, RAD51 foci, DNA repair and cell-cycle assays tracking CDT1, p21, Claspin accumulation","pmids":["25025768"],"confidence":"Medium","gaps":["Single-lab cell-based study","Direct contribution of each substrate to the HR defect not dissected"]},{"year":2017,"claim":"Demonstrated that the DCN1-UBC12 interaction confers cullin selectivity, establishing DCN1 as a co-E3 specifically required for CUL3 neddylation.","evidence":"Biochemical Ki determination with the DI-591 inhibitor and cellular cullin neddylation profiling","pmids":["29074978"],"confidence":"High","gaps":["Mechanism of selectivity for CUL3 over other cullins not fully resolved"]},{"year":2018,"claim":"Mapped the structural basis of DCN1 recognition to the UBE2M N-terminal peptide, enabling selective inhibition of CUL3 neddylation.","evidence":"Co-crystal structure of a peptidomimetic with DCN1 plus SPR/ITC binding and cellular neddylation assays","pmids":["29438612"],"confidence":"High","gaps":["Does not explain why CUL3 is preferentially affected","In vivo relevance of selective CUL3 inhibition not tested"]},{"year":2018,"claim":"Revealed UBE2M as a dual-function enzyme that can switch from neddylation to ubiquitylation, degrading the sister E2 UBE2F under stress.","evidence":"Reciprocal Co-IP, in vitro ubiquitylation/neddylation assays, mass spectrometry, and viability assays in lung cancer cells","pmids":["29932898"],"confidence":"High","gaps":["Structural determinant of the neddylation-to-ubiquitylation switch unknown","Generality of the ubiquitylation activity beyond UBE2F unclear"]},{"year":2019,"claim":"Consolidated the tumor-suppressive-substrate model, showing UBE2M loss stabilizes p21, p27, and Wee1 to arrest the cell cycle even in MLN4924-resistant cells.","evidence":"siRNA knockdown, quantitative proteomics, flow cytometry, and xenografts in lung cancer","pmids":["31208947"],"confidence":"Medium","gaps":["Single-lab study","Did not separate effects across individual cullins"]},{"year":2021,"claim":"Identified protein partners that couple UBE2M to p53 regulation and to its own stabilization, linking neddylation to tumor-suppressor control.","evidence":"Co-IP and immunofluorescence with MDM2, L11, and NPRL2, plus rescue and xenograft assays","pmids":["34638383","33905671"],"confidence":"Medium","gaps":["No reciprocal IP reported for the MDM2/L11 interactions","Whether these partners are neddylation substrates not established"]},{"year":2023,"claim":"Established UBE2M as a regulator of innate immunity and inflammation through neddylation of TRIM21 and control of RIG-I, embedded in a STAT1-TRIM21 negative feedback loop.","evidence":"Macrophage-specific knockout mice, site-specific neddylation mutagenesis (TRIM21 K129/134), Co-IP, and virus-infection models","pmids":["37343564","36662617"],"confidence":"High","gaps":["How UBE2M discriminates non-cullin substrates from cullins unresolved","Direct demonstration of TRIM21 as the UBE2M-degrading E3 relies on single-lab data"]},{"year":2022,"claim":"Showed a cell-type-intrinsic requirement for the UBE2M-RBX1 neddylation axis in regulatory T cell homeostasis and immune tolerance.","evidence":"Treg-specific conditional knockout mice with immunophenotyping and genetic epistasis against Rbx1","pmids":["35641500"],"confidence":"High","gaps":["Specific CRL substrates underlying the Treg phenotype not identified"]},{"year":2025,"claim":"Uncovered upstream post-translational and species-specific regulation of UBE2M itself via PRMT1 methylation and a primate-restricted PINK1 interaction.","evidence":"PRMT1 conditional mice with R169 mutagenesis and GST-pulldown; PINK1 knockdown across monkey, mouse, and pig with proteomics","pmids":["40744915","41298302"],"confidence":"Medium","gaps":["Mechanism by which PINK1 stabilizes UBE2M unknown","Single-lab evidence for each regulatory axis"]},{"year":2026,"claim":"Expanded the non-cullin neddylation substrate repertoire (MKK7, NAA10, USP39, EGFR, VEGFR2), showing UBE2M stabilizes diverse signaling proteins across tissue contexts.","evidence":"Co-IP, proximity ligation, cycloheximide chase, site-specific mutagenesis, and conditional knockout/disease models","pmids":["41361309","41857595","41680469","42111190","42209461"],"confidence":"Medium","gaps":["Whether RBX1-CUL E3s are required for all non-cullin substrates not generalized","Each substrate validated by a single lab"]},{"year":2026,"claim":"Broadened UBE2M's enzymatic scope beyond NEDD8 to URM1 conjugation and identified Orlistat as a direct UBC12 inhibitor, linking the enzyme to Wnt signaling.","evidence":"Activity-based URM1 probe with proteomics; ITC binding (KD 678 nM) and neddylation activity assays with Orlistat","pmids":["42056084","42067003"],"confidence":"Medium","gaps":["Physiological substrates of UBE2M-dependent urmylation undefined","DCN1 role in URM1 conjugation only inferred pharmacologically"]},{"year":null,"claim":"How UBE2M selects between neddylation versus ubiquitylation activity, and between cullin versus the many non-cullin substrates, remains mechanistically unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model explaining substrate switching","No unifying determinant for non-cullin substrate recognition","Whether DCN1 family co-E3s govern non-cullin neddylation is untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[1,6,14,17,18,19,20]},{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[1,0,2]},{"term_id":"GO:0031386","term_label":"protein tag activity","supporting_discovery_ids":[1,6]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[11]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[11,12]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[1,0,2]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[5,9,19]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[5]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[6,7,8]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[14,18,20,21]}],"complexes":[],"partners":["UBA3","DCN1","TRIM21","MDM2","RPL11","NPRL2","PINK1","PRMT1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P61081","full_name":"NEDD8-conjugating enzyme Ubc12","aliases":["NEDD8 carrier protein","Ubiquitin-conjugating enzyme E2 M"],"length_aa":183,"mass_kda":20.9,"function":"Accepts the ubiquitin-like protein NEDD8 from the UBA3-NAE1 E1 complex and catalyzes its covalent attachment to other proteins. The specific interaction with the E3 ubiquitin ligase RBX1, but not RBX2, suggests that the RBX1-UBE2M complex neddylates specific target proteins, such as CUL1, CUL2, CUL3 and CUL4. Involved in cell proliferation","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/P61081/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/UBE2M","classification":"Common Essential","n_dependent_lines":1169,"n_total_lines":1208,"dependency_fraction":0.9677152317880795},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000130725","cell_line_id":"CID001610","localizations":[{"compartment":"nucleoplasm","grade":3},{"compartment":"cytoplasmic","grade":2}],"interactors":[{"gene":"NEDD8;NEDD8-MDP1","stoichiometry":4.0},{"gene":"SRPR","stoichiometry":0.2},{"gene":"SRPRB","stoichiometry":0.2},{"gene":"UBA3","stoichiometry":0.2},{"gene":"NAE1","stoichiometry":0.2},{"gene":"DCP2","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID001610","total_profiled":1310},"omim":[{"mim_id":"616522","title":"DCN1 DOMAIN-CONTAINING PROTEIN 5; DCUN1D5","url":"https://www.omim.org/entry/616522"},{"mim_id":"616167","title":"DCN1 DOMAIN-CONTAINING PROTEIN 3; DCUN1D3","url":"https://www.omim.org/entry/616167"},{"mim_id":"610553","title":"UBIQUITIN-FOLD MODIFIER 1; UFM1","url":"https://www.omim.org/entry/610553"},{"mim_id":"603385","title":"NEDD8-ACTIVATING ENZYME E1, SUBUNIT 1; NAE1","url":"https://www.omim.org/entry/603385"},{"mim_id":"603173","title":"UBIQUITIN-CONJUGATING ENZYME E2 M; UBE2M","url":"https://www.omim.org/entry/603173"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Nucleoplasm","reliability":"Enhanced"},{"location":"Nucleoli","reliability":"Additional"},{"location":"Nuclear bodies","reliability":"Additional"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in 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The E1's Ubc12-binding domain resembles ubiquitin and recruits Ubc12 in a manner mimicking ubiquitin's interactions with ubiquitin-binding domains. Structural comparison with E2-E3 complexes indicates that the E1 and E3 binding sites on Ubc12 may overlap.\",\n      \"method\": \"X-ray crystallography of E1-E2 complex combined with mutational analysis\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — crystal structure determination with supporting mutational analyses in a focused mechanistic study\",\n      \"pmids\": [\"15694336\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"UBC12 (UBE2M) is the E2 conjugating enzyme for NEDD8. The catalytic cysteine C111 is essential for NEDD8 transfer; the C111S point mutant forms a stable heterodimeric conjugate with NEDD8 (resistant to 6M guanidine HCl, urea, SDS, and β-mercaptoethanol), sequesters NEDD8, and acts as a dominant-negative inhibitor of NEDD8 conjugation to cullins (Cul-1, Cul-2) and other substrates. Overexpression of the dominant-negative mutant inhibits growth of U2OS and HEK293 cells.\",\n      \"method\": \"Active-site mutagenesis (C111S), dominant-negative overexpression, in vivo NEDD8 conjugation assays, cell growth assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — active-site mutagenesis with biochemical validation and cell-growth functional readout in a focused study\",\n      \"pmids\": [\"10828074\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"UBE2M functions as a dual E2 enzyme: under physiological conditions it acts as a neddylation E2 to activate CUL3-Keap1 E3; under stress conditions (induced by HIF-1 and AP1 transactivation) it switches to a ubiquitylation E2 that, together with Parkin-DJ-1 E3, mediates targeted ubiquitylation and proteasomal degradation of the other neddylation E2, UBE2F. UBE2M-induced UBE2F degradation inactivates CRL5 and causes NOXA accumulation, suppressing lung cancer cell growth.\",\n      \"method\": \"Co-IP, siRNA knockdown, overexpression, ubiquitylation and neddylation assays, mass spectrometry, cell viability assays\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP plus in vitro ubiquitylation/neddylation assays and multiple functional readouts in a single focused study\",\n      \"pmids\": [\"29932898\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"The DCN1-UBC12 protein-protein interaction is required for cellular neddylation of cullin 3 specifically; small-molecule inhibitor DI-591 (Ki ~10–12 nM for DCN1/DCN2) disrupts this interaction and selectively converts cullin 3 to an un-neddylated inactive form with minimal effect on other cullins, establishing a specific role of the DCN1-UBC12 interaction in CUL3 neddylation.\",\n      \"method\": \"Biochemical binding assays (Ki determination), cell-based co-immunoprecipitation, western blotting for cullin neddylation, small-molecule inhibitor DI-591\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — biochemical binding assays combined with cellular neddylation profiling, independently consistent with multiple inhibitor studies\",\n      \"pmids\": [\"29074978\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"A UBC12 N-terminal peptide (12 residues) mediates high-affinity binding to the co-E3 DCN1; peptidomimetic inhibitors based on this peptide bind DCN1 with KD < 10 nM. Co-crystal structure of a potent peptidomimetic with DCN1 provides the structural basis for the DCN1-UBC12 interaction interface. Cellular inhibition selectively blocks cullin 3 neddylation.\",\n      \"method\": \"Co-crystal structure determination, surface plasmon resonance/ITC binding assays, cellular neddylation assays\",\n      \"journal\": \"Journal of medicinal chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — co-crystal structure with functional cellular validation, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"29438612\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"UBE2M is required for DNA damage repair and genome integrity. UBE2M knockdown increases DNA breaks, sensitizes cells to DNA damaging agents, and impairs RAD51 foci formation (homologous recombination). The downstream mechanism involves activation of Cullin 1, 2, and 4 ligases; specifically, loss of CUL2 neddylation blocks G1-to-S progression and delays S-phase DNA damage response, while loss of CUL4 neddylation causes elevated DNA breakages. Key CRL substrates CDT1, p21, and Claspin accumulate upon UBE2M knockdown and contribute to the elevated DNA damage phenotype.\",\n      \"method\": \"siRNA knockdown, RAD51 foci formation assay, cell-based DNA repair assays, flow cytometry (cell cycle), immunofluorescence\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal cell-based assays (RAD51 foci, DNA repair, cell cycle), single lab\",\n      \"pmids\": [\"25025768\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"UBE2M mediates neddylation of E3 ubiquitin ligase TRIM21 at K129/134. This neddylation promotes TRIM21-dependent recruitment and ubiquitination-mediated degradation of the E3 ligase VHL. VHL loss stabilizes HIF-1α, increasing IL-1β production in macrophages, driving obesity-related inflammation.\",\n      \"method\": \"Macrophage-specific UBE2M knockout mice, co-IP, neddylation site mutagenesis (K129/134), western blotting, cytokine measurement, metabolic phenotyping\",\n      \"journal\": \"Cell metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo knockout model combined with site-specific mutagenesis and multiple orthogonal mechanistic assays\",\n      \"pmids\": [\"37343564\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"UBE2M inhibits RIG-I degradation in macrophages by preventing the interaction of RIG-I with the E3 ligase STUB1, thereby sustaining antiviral IFN-I signaling. Conversely, IFN-I-activated STAT1 transcriptionally upregulates TRIM21, which promotes UBE2M degradation, forming a negative feedback loop. TRIM21 acts as an E3 to degrade UBE2M.\",\n      \"method\": \"UBE2M-deficient macrophages, RNA-virus infection models, Co-IP, siRNA knockdown, reporter and protein stability assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP plus UBE2M-deficient macrophage model, multiple mechanistic readouts, single lab\",\n      \"pmids\": [\"36662617\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Treg cell-specific deletion of Ube2m (neddylation E2) in mice causes disrupted Treg cell homeostasis and suppressive functions with an inflammatory disorder phenotype, demonstrating that the Ube2m-Rbx1 neddylation axis is specifically required for intrinsic regulatory processes in Treg cells. The phenotype is similar to but less severe than Rbx1 deletion, suggesting Rbx1 also has Ube2m-independent roles.\",\n      \"method\": \"Conditional knockout mice (Treg-specific Ube2m deletion), flow cytometry, immunophenotyping, inflammatory disease assessment\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo conditional knockout with rigorous immunophenotyping and genetic epistasis (Ube2m vs Rbx1 vs Ube2f deletions compared)\",\n      \"pmids\": [\"35641500\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"UBC12/UBE2M knockdown in lung cancer cells inhibits cullin neddylation, inactivates CRL E3 ligases, and causes accumulation of tumor-suppressive CRL substrates p21, p27, and Wee1, triggering G2-phase cell-cycle arrest and suppressing malignant phenotypes in vitro and in vivo. UBC12 knockdown also inhibits growth of MLN4924-resistant lung cancer cells.\",\n      \"method\": \"siRNA knockdown, quantitative proteomics, flow cytometry (cell cycle), western blotting, xenograft mouse model\",\n      \"journal\": \"EBioMedicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (proteomics, FACS, in vivo xenograft), single lab\",\n      \"pmids\": [\"31208947\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"UBE2M mediates gemcitabine-induced degradation of p27(Kip1) protein in human urothelial carcinoma cells. Gemcitabine induces UBE2M expression via a PI3K-dependent pathway; silencing UBE2M with siRNA restores p27(Kip1) levels and reduces gemcitabine sensitivity, establishing UBE2M as a mediator of drug cytotoxicity through p27(Kip1) degradation.\",\n      \"method\": \"2D gel electrophoresis, siRNA knockdown, proteasome inhibitor (MG132), PI3K inhibitor (LY294002), western blotting, cell sensitivity assays\",\n      \"journal\": \"Biochemical pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological and siRNA approaches with multiple mechanistic readouts, single lab\",\n      \"pmids\": [\"21477582\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"UBE2M physically binds to MDM2 and to ribosomal protein L11 (but not directly to p53) in HCC cells, as shown by co-IP and immunofluorescence colocalization. UBE2M depletion activates p53 expression and stability; conversely, ectopic UBE2M enhances MDM2-mediated degradation of exogenous p53. L11 is required for p53 activation upon UBE2M depletion.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence colocalization, overexpression/knockdown, western blotting, xenograft mouse model\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP and colocalization with functional rescue experiments, single lab, no reciprocal IP reported\",\n      \"pmids\": [\"34638383\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"NPRL2 physically interacts with UBE2M (validated by Co-IP and immunofluorescence), and this interaction increases NPRL2 protein stability by reducing its polyubiquitination and proteasomal degradation. NPRL2 cooperatively enhances UBE2M-mediated neddylation and CRL substrate degradation.\",\n      \"method\": \"Co-immunoprecipitation, immunofluorescence, ubiquitination assays, siRNA knockdown, in vivo xenograft\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP validated with IF and functional assays, single lab\",\n      \"pmids\": [\"33905671\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PINK1 interacts with UBC12 (UBE2M) in the primate brain; knockdown of PINK1 in monkeys (but not in PINK1-knockout mice or pigs) markedly reduces UBC12 protein abundance and global neddylation levels, revealing a primate-specific PINK1-UBC12 axis regulating protein neddylation.\",\n      \"method\": \"Mass spectrometry proteomics, PINK1 knockdown in monkeys, colocalization imaging, western blotting for neddylation\",\n      \"journal\": \"Zoological research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — MS-based identification of interaction with in vivo primate knockdown validation and cross-species comparison\",\n      \"pmids\": [\"41298302\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"UBE2M neddylates MKK7 (mitogen-activated protein kinase kinase 7) as a direct substrate. Neddylation of MKK7 inhibits its ubiquitination and proteasomal degradation, stabilizing MKK7 and enhancing its phosphorylation. Stabilized MKK7 activates JNK signaling, induces EGR1, and suppresses CCND2 expression to restrain melanoma cell proliferation.\",\n      \"method\": \"Co-IP, proximity ligation assay, cycloheximide chase assay, transcriptomic analysis, in vitro and in vivo functional assays\",\n      \"journal\": \"Journal of translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct neddylation substrate identification with multiple orthogonal methods (Co-IP, PLA, CHX chase), single lab\",\n      \"pmids\": [\"41361309\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PRMT1 methylates UBE2M at arginine R169, enhancing its protein function. This UBE2M post-translational modification increases neddylation and protein stability of NEDD4, which in turn ubiquitinates PPARγ for degradation, inhibiting fatty acid metabolism in renal tubular cells during calcium oxalate crystal-induced injury.\",\n      \"method\": \"Conditional PRMT1 knockout/overexpression mice, immunoprecipitation, mass spectrometry, GST-pulldown, site-specific mutagenesis (R169), single-cell RNA-seq, metabolomics\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — site-specific mutagenesis with in vivo mouse model and multiple orthogonal biochemical methods, single lab\",\n      \"pmids\": [\"40744915\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"NAE1/UBA3 and UBE2M serve as the E1 and E2 enzymes, respectively, for URM1 (ubiquitin-related modifier 1) protein modification (urmylation) in human cells under normal and oxidative stress conditions. Pharmacological inhibition of the UBE2M-DCN1 module suggests DCN1 may contribute to URM1 conjugation.\",\n      \"method\": \"Activity-based URM1 probe to covalently capture cysteine enzymes, proteomic characterization, cell-based validation, pharmacological inhibition (pevonedistat)\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — activity-based probe with proteomic and cell-based validation, single study\",\n      \"pmids\": [\"42056084\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"UBE2M neddylates NAA10 (N-alpha-acetyltransferase 10) as a direct substrate at lysine K148, with RBX1-CUL4A acting as the critical E3 ligase for this modification. UBE2M-mediated neddylation of NAA10 enhances its protein stability and functional activity, promoting prostate cancer cell proliferation.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, proximity ligation assay, neddylation site mutagenesis (K148), in vitro and in vivo functional assays\",\n      \"journal\": \"Journal of translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — site-specific neddylation site identified with MS and PLA, single lab\",\n      \"pmids\": [\"41857595\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"UBE2M directly neddylates VEGFR2 in pulmonary endothelial cells, stabilizing the receptor. UBE2M deficiency in mice reduces VEGFR2 protein levels and phosphorylation, causing premature pulmonary vascular aging and structural disruption, while UBE2M reconstitution alleviates cellular senescence in a doxorubicin-induced model.\",\n      \"method\": \"Ube2m conditional knockout mice, neddylation assay, western blotting, immunofluorescence, doxorubicin senescence model, in vivo emphysema model\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo knockout model with biochemical neddylation assays and reconstitution, single lab\",\n      \"pmids\": [\"42209461\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"UBE2M neddylates USP39, which in turn modulates deubiquitination of PABPC1, enhancing translation efficiency of CCNB1 and promoting G2/M cell cycle progression in colorectal cancer cells.\",\n      \"method\": \"Co-IP, in vivo and in vitro functional experiments, single-cell and bulk transcriptomics, protein stability assays\",\n      \"journal\": \"Experimental & molecular medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — novel neddylation substrate (USP39) identified with Co-IP and functional pathway validation, single lab\",\n      \"pmids\": [\"41680469\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"UBE2M neddylates EGFR in keratinocytes, stabilizing and activating EGFR signaling. UBE2M is upregulated in psoriatic lesions and promotes keratinocyte proliferation and inflammatory responses through EGFR neddylation; genetic and pharmacological inhibition of UBE2M suppresses psoriasis-like development.\",\n      \"method\": \"Immunofluorescence in human and murine psoriasis lesions, UBE2M knockdown/overexpression, neddylation assays, IMQ-induced murine psoriasis model\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct neddylation substrate (EGFR) identified with in vivo disease model validation, single lab\",\n      \"pmids\": [\"42111190\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"Orlistat directly binds UBC12 (UBE2M) with a KD of 678 nM (ITC assay), inhibits UBC12's NEDD8-conjugating activity, and blocks UBC12's interaction with DCN1, selectively suppressing cullin 1 neddylation. UBC12 overexpression positively regulates Wnt/β-catenin signaling, and UBC12 depletion abrogates Orlistat's inhibition of Wnt signaling.\",\n      \"method\": \"Isothermal titration calorimetry (ITC), neddylation activity assays, co-immunoprecipitation, western blotting, overexpression/knockdown\",\n      \"journal\": \"Pharmacological research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — direct binding measured by ITC plus functional neddylation assays, single lab\",\n      \"pmids\": [\"42067003\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"UBE2M maintains ERα expression by inhibiting its ubiquitination and degradation through a UBE2M-CUL3/4A-E6AP-ERα axis in ER-positive breast cancer. ERα in turn enhances HIF-1α-mediated transcription of UBE2M, forming a positive feedback loop. Silencing UBE2M suppresses growth and sensitizes cells to fulvestrant in vitro and in vivo.\",\n      \"method\": \"siRNA knockdown, overexpression, ubiquitination assays, co-IP, western blotting, xenograft mouse model\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ubiquitination assays with Co-IP and in vivo validation, single lab\",\n      \"pmids\": [\"39138151\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"UBE2M (hUbc12/UBC12) is the primary E2 NEDD8-conjugating enzyme that accepts activated NEDD8 from the E1 (NAE1/UBA3) via its catalytic cysteine (C111) and transfers NEDD8 to substrate proteins, most prominently cullin family members (CUL1–5) to activate Cullin-RING E3 ligases (CRLs); the co-E3 DCN1 binds the UBE2M N-terminus to specifically enhance CUL1 and CUL3 neddylation; UBE2M can also act as a ubiquitylation E2 (e.g., for UBE2F degradation via Parkin-DJ-1 under stress), neddylates non-cullin substrates including TRIM21, MKK7, EGFR, VEGFR2, NAA10, USP39, and is itself regulated by PRMT1-mediated arginine methylation at R169, TRIM21-mediated ubiquitination (negative feedback downstream of STAT1/IFN-I), and a primate-specific interaction with PINK1 that stabilizes UBE2M protein.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"UBE2M (hUbc12/UBC12) is the primary E2 NEDD8-conjugating enzyme that drives neddylation of cullin-RING E3 ligases, coupling protein modification to cell-cycle, DNA-repair, immune, and metabolic programs [#1, #5]. It is charged with activated NEDD8 by the NEDD8 E1 (APPBP1-UBA3), which recruits UBE2M through a ubiquitin-like binding domain that engages the E2 catalytic core in a manner overlapping the E3-binding surface, and transfer to substrates requires the essential active-site cysteine C111 [#0, #1]. Substrate specificity is sharpened by the co-E3 DCN1, which binds a 12-residue N-terminal UBE2M peptide; this interaction is selectively required for neddylation of cullin 3 (and cullin 1), and disrupting it with peptidomimetic or small-molecule inhibitors converts these cullins to inactive un-neddylated forms [#3, #4, #21]. Through cullin neddylation UBE2M activates CRLs that turn over key substrates including CDT1, p21, p27, Wee1, and Claspin, so its loss stabilizes these factors, blocks cell-cycle progression, impairs RAD51-dependent homologous recombination, and elevates DNA damage [#5, #9]. Beyond cullins, UBE2M directly neddylates a growing set of non-cullin substrates — TRIM21, MKK7, EGFR, VEGFR2, NAA10, and USP39 — typically stabilizing them by antagonizing their ubiquitin-mediated degradation, thereby tuning inflammatory, MAPK/JNK, receptor-tyrosine-kinase, and translation pathways [#6, #14, #17, #18, #19, #20]. UBE2M can also act as a ubiquitylation E2: under stress it partners with Parkin-DJ-1 to degrade the sister neddylation E2 UBE2F, inactivating CRL5 [#2]. Its own activity and abundance are controlled by PRMT1-mediated arginine methylation at R169, by TRIM21-mediated ubiquitination in a STAT1/IFN-I negative-feedback loop, and by a primate-specific PINK1 interaction that sustains UBE2M protein levels [#7, #13, #15].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Established UBE2M as the dedicated E2 for NEDD8 and pinpointed the catalytic residue, answering how NEDD8 is transferred to cullins.\",\n      \"evidence\": \"Active-site C111S mutagenesis, dominant-negative overexpression, and in vivo NEDD8 conjugation assays in U2OS/HEK293 cells\",\n      \"pmids\": [\"10828074\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not define the E1 or E3 interaction interfaces\", \"Substrate range beyond Cul-1/Cul-2 not mapped\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Resolved how the NEDD8 E1 recruits UBE2M, showing the E1 uses a ubiquitin-like domain to engage the E2 and that E1- and E3-binding sites may overlap.\",\n      \"evidence\": \"X-ray crystallography of the APPBP1-UBA3 / Ubc12 complex with mutational analysis\",\n      \"pmids\": [\"15694336\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Static structure does not capture the thioester transfer step\", \"Does not address DCN1-dependent specificity\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Linked UBE2M to drug cytotoxicity by showing it mediates degradation of the CDK inhibitor p27(Kip1), connecting neddylation to chemotherapy response.\",\n      \"evidence\": \"2D gel electrophoresis, siRNA knockdown, PI3K and proteasome inhibitors in urothelial carcinoma cells\",\n      \"pmids\": [\"21477582\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not establish which CRL mediates p27 turnover\", \"Single cell-type context\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined a genome-integrity role, showing UBE2M-dependent neddylation of CUL2 and CUL4 controls cell-cycle progression and DNA repair.\",\n      \"evidence\": \"siRNA knockdown, RAD51 foci, DNA repair and cell-cycle assays tracking CDT1, p21, Claspin accumulation\",\n      \"pmids\": [\"25025768\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab cell-based study\", \"Direct contribution of each substrate to the HR defect not dissected\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Demonstrated that the DCN1-UBC12 interaction confers cullin selectivity, establishing DCN1 as a co-E3 specifically required for CUL3 neddylation.\",\n      \"evidence\": \"Biochemical Ki determination with the DI-591 inhibitor and cellular cullin neddylation profiling\",\n      \"pmids\": [\"29074978\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of selectivity for CUL3 over other cullins not fully resolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Mapped the structural basis of DCN1 recognition to the UBE2M N-terminal peptide, enabling selective inhibition of CUL3 neddylation.\",\n      \"evidence\": \"Co-crystal structure of a peptidomimetic with DCN1 plus SPR/ITC binding and cellular neddylation assays\",\n      \"pmids\": [\"29438612\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not explain why CUL3 is preferentially affected\", \"In vivo relevance of selective CUL3 inhibition not tested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Revealed UBE2M as a dual-function enzyme that can switch from neddylation to ubiquitylation, degrading the sister E2 UBE2F under stress.\",\n      \"evidence\": \"Reciprocal Co-IP, in vitro ubiquitylation/neddylation assays, mass spectrometry, and viability assays in lung cancer cells\",\n      \"pmids\": [\"29932898\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural determinant of the neddylation-to-ubiquitylation switch unknown\", \"Generality of the ubiquitylation activity beyond UBE2F unclear\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Consolidated the tumor-suppressive-substrate model, showing UBE2M loss stabilizes p21, p27, and Wee1 to arrest the cell cycle even in MLN4924-resistant cells.\",\n      \"evidence\": \"siRNA knockdown, quantitative proteomics, flow cytometry, and xenografts in lung cancer\",\n      \"pmids\": [\"31208947\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab study\", \"Did not separate effects across individual cullins\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified protein partners that couple UBE2M to p53 regulation and to its own stabilization, linking neddylation to tumor-suppressor control.\",\n      \"evidence\": \"Co-IP and immunofluorescence with MDM2, L11, and NPRL2, plus rescue and xenograft assays\",\n      \"pmids\": [\"34638383\", \"33905671\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No reciprocal IP reported for the MDM2/L11 interactions\", \"Whether these partners are neddylation substrates not established\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Established UBE2M as a regulator of innate immunity and inflammation through neddylation of TRIM21 and control of RIG-I, embedded in a STAT1-TRIM21 negative feedback loop.\",\n      \"evidence\": \"Macrophage-specific knockout mice, site-specific neddylation mutagenesis (TRIM21 K129/134), Co-IP, and virus-infection models\",\n      \"pmids\": [\"37343564\", \"36662617\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How UBE2M discriminates non-cullin substrates from cullins unresolved\", \"Direct demonstration of TRIM21 as the UBE2M-degrading E3 relies on single-lab data\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Showed a cell-type-intrinsic requirement for the UBE2M-RBX1 neddylation axis in regulatory T cell homeostasis and immune tolerance.\",\n      \"evidence\": \"Treg-specific conditional knockout mice with immunophenotyping and genetic epistasis against Rbx1\",\n      \"pmids\": [\"35641500\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific CRL substrates underlying the Treg phenotype not identified\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Uncovered upstream post-translational and species-specific regulation of UBE2M itself via PRMT1 methylation and a primate-restricted PINK1 interaction.\",\n      \"evidence\": \"PRMT1 conditional mice with R169 mutagenesis and GST-pulldown; PINK1 knockdown across monkey, mouse, and pig with proteomics\",\n      \"pmids\": [\"40744915\", \"41298302\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which PINK1 stabilizes UBE2M unknown\", \"Single-lab evidence for each regulatory axis\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Expanded the non-cullin neddylation substrate repertoire (MKK7, NAA10, USP39, EGFR, VEGFR2), showing UBE2M stabilizes diverse signaling proteins across tissue contexts.\",\n      \"evidence\": \"Co-IP, proximity ligation, cycloheximide chase, site-specific mutagenesis, and conditional knockout/disease models\",\n      \"pmids\": [\"41361309\", \"41857595\", \"41680469\", \"42111190\", \"42209461\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether RBX1-CUL E3s are required for all non-cullin substrates not generalized\", \"Each substrate validated by a single lab\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Broadened UBE2M's enzymatic scope beyond NEDD8 to URM1 conjugation and identified Orlistat as a direct UBC12 inhibitor, linking the enzyme to Wnt signaling.\",\n      \"evidence\": \"Activity-based URM1 probe with proteomics; ITC binding (KD 678 nM) and neddylation activity assays with Orlistat\",\n      \"pmids\": [\"42056084\", \"42067003\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Physiological substrates of UBE2M-dependent urmylation undefined\", \"DCN1 role in URM1 conjugation only inferred pharmacologically\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How UBE2M selects between neddylation versus ubiquitylation activity, and between cullin versus the many non-cullin substrates, remains mechanistically unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model explaining substrate switching\", \"No unifying determinant for non-cullin substrate recognition\", \"Whether DCN1 family co-E3s govern non-cullin neddylation is untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1, 6, 14, 17, 18, 19, 20]},\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [1, 0, 2]},\n      {\"term_id\": \"GO:0061650\", \"supporting_discovery_ids\": [1]},\n      {\"term_id\": \"GO:0031386\", \"supporting_discovery_ids\": [1, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [11]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [11, 12]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 0, 2]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [5, 9, 19]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [5]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [6, 7, 8]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [14, 18, 20, 21]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"UBA3\", \"DCN1\", \"TRIM21\", \"MDM2\", \"RPL11\", \"NPRL2\", \"PINK1\", \"PRMT1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":7,"faith_total":7,"faith_pct":100.0}}