Affinage

UBE2L6

Ubiquitin/ISG15-conjugating enzyme E2 L6 · UniProt O14933

Length
153 aa
Mass
17.8 kDa
Annotated
2026-04-28
30 papers in source corpus 17 papers cited in narrative 17 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

UBE2L6 (UbcH8) is a dual-specificity E2 ubiquitin/ISG15-conjugating enzyme that operates at the intersection of the ubiquitin-proteasome system and the interferon-stimulated ISGylation pathway. As an ISG15 E2, it receives ISG15 from the E1 enzyme UBA7 through a thioester intermediate governed by specific contacts in the UBA7 ubiquitin-fold domain and catalytic cysteine loop conformations, then transfers ISG15 exclusively to HECT-family E3 ligases (notably HERC5) in a closed-conformation-dependent mechanism, modifying substrates such as RIG-I and STAT1 to regulate innate immune signaling and macrophage polarization (PMID:15131269, PMID:41773046, PMID:37820603). As a ubiquitin E2, UBE2L6 partners with RING/IBR-type E3 ligases including SIAH1, CRL4^Cdt2, and UBR4 to target substrates—FLT3-ITD, p21, Set8, EZH2, and ATGL—for K48-linked polyubiquitination and proteasomal degradation, thereby influencing cell cycle progression, the DNA damage response, lipid metabolism, and chromatin regulation (PMID:21628527, PMID:20508617, PMID:36906655, PMID:33712284). The protein exists in a concentration-dependent monomer–dimer equilibrium, with a backside dimerization interface that modulates E1 and E3 interaction surfaces, providing a potential mechanism for tuning its conjugating activities (PMID:39346869).

Mechanistic history

Synthesis pass · year-by-year structured walk · 11 steps
  1. 1999 Medium

    Establishing that UBE2L6 selectively engages RING/IBR-type E3 ligases answered the question of which E3 classes this E2 partners with, linking it to the RBR E3 ligase family.

    Evidence Yeast two-hybrid and in vitro binding assays showing specific interaction with HHARI and H7-AP1 RING/IBR domains

    PMID:10521492

    Open questions at the time
    • No ubiquitination assay performed to demonstrate functional consequence of binding
    • Identity of substrates ubiquitinated through these E3 partners unknown
  2. 2004 High

    Identification of UBE2L6 as the principal E2 for ISG15 conjugation established its dual specificity for both ubiquitin and ISG15, redefining its biological scope beyond the ubiquitin system.

    Evidence In vitro thioester formation and ISG15 transfer assays with purified components, validated by RNAi knockdown in cells

    PMID:15131269

    Open questions at the time
    • E3 ligase(s) mediating ISG15 transfer not yet identified
    • Full range of ISG15 substrates unknown
  3. 2007 Medium

    Demonstration that UBE2L6 mediates both ubiquitin and ISG15 conjugation to RIG-I, with cross-regulation by RNF125, revealed a molecular switch mechanism controlling innate immune sensor stability.

    Evidence Ectopic expression, co-immunoprecipitation, and functional reporter assays in mammalian cells

    PMID:17719635

    Open questions at the time
    • No in vitro reconstitution of the cross-regulatory circuit
    • Stoichiometry and kinetics of the ubiquitin/ISG15 competition on RIG-I not determined
  4. 2009 High

    Solving the NMR structure of the UbcH8–ubiquitin covalent complex revealed a unique ubiquitin-interaction surface, explaining how this E2 accommodates both ubiquitin and ISG15 while retaining E1/E3 binding capacity.

    Evidence NMR spectroscopy with chemical shift perturbation and cross-saturation experiments on a disulfide-linked UbcH8~Ub mimic

    PMID:19928833

    Open questions at the time
    • Analogous ISG15-conjugate structure not determined at this point
    • Functional impact of the unique interaction surface on catalysis not tested by mutagenesis
  5. 2010 Medium

    Identification of the SIAH1–UBE2L6 partnership targeting FLT3-ITD for K48-linked ubiquitination and degradation connected UBE2L6 to oncogenic kinase turnover in leukemia.

    Evidence Co-immunoprecipitation, siRNA knockdown, overexpression, and proteasome inhibitor experiments in leukemia cell lines

    PMID:20508617

    Open questions at the time
    • No in vitro reconstitution of SIAH1–UBE2L6-mediated FLT3-ITD ubiquitination
    • Whether tyrosine phosphorylation creates a direct degron recognized by SIAH1 not structurally resolved
  6. 2011 High

    Demonstrating that UBE2L6 is the substrate-selective E2 for CRL4^Cdt2-mediated degradation of p21 and Set8 (but not Cdt1) revealed that a single E3 complex uses different E2 enzymes for different substrates, and linked UBE2L6 to cell cycle control and DNA damage response.

    Evidence Proteomic Co-IP/MS, RNAi screening, siRNA knockdown with cell cycle and UV-damage phenotypic readouts

    PMID:21628527

    Open questions at the time
    • Structural basis for substrate-selective E2 usage within CRL4^Cdt2 not determined
    • Whether UBE2L6 directly contacts p21 or Set8 unknown
  7. 2020 Medium

    Adipose-specific Ube2l6 knockout established UBE2L6 as a physiological regulator of lipid metabolism by promoting ATGL ubiquitination and degradation, controlling lipolysis and adiposity in vivo.

    Evidence Conditional knockout mouse model with ubiquitylation assays and comprehensive metabolic phenotyping

    PMID:33712284

    Open questions at the time
    • E3 ligase partnering with UBE2L6 for ATGL ubiquitination not identified
    • Whether the effect is cell-autonomous in adipocytes not fully dissected
  8. 2023 Medium

    Identification of UBR4 as the E3 partner for UBE2L6-mediated EZH2 K381 ubiquitination, regulated by UHRF1-dependent promoter methylation of UBE2L6, connected this E2 to epigenetic regulation and melanoma pigmentation state.

    Evidence Co-IP, ubiquitination assay with K381 mutagenesis, siRNA, xenograft studies, and promoter methylation analysis in melanoma cells

    PMID:36906655

    Open questions at the time
    • In vitro reconstitution of UBR4–UBE2L6-mediated EZH2 ubiquitination not performed
    • Whether UBE2L6 regulation of EZH2 operates in non-melanoma contexts unknown
  9. 2023 Medium

    Demonstration that UBE2L6 promotes STAT1 ISGylation to drive M1 macrophage polarization in obesity extended its ISGylation function to metabolic inflammation.

    Evidence Adipose-specific knockout mouse model with Co-IP confirming UBE2L6–STAT1 interaction, flow cytometry, and cytokine profiling

    PMID:37820603

    Open questions at the time
    • E3 ligase mediating STAT1 ISGylation not identified
    • ISGylation site(s) on STAT1 not mapped
    • Whether this is direct ISGylation or requires intermediary factors unknown
  10. 2024 Medium

    Discovery of a concentration-dependent monomer–dimer equilibrium with a backside dimerization interface that allosterically modulates E1/E3 binding surfaces introduced oligomerization as a regulatory mechanism for UBE2L6 activity.

    Evidence SAXS and NMR spectroscopy with GST-fusion dissociation experiments

    PMID:39346869

    Open questions at the time
    • Functional consequence of dimerization on catalytic rate or substrate specificity not demonstrated in activity assays
    • Whether dimerization occurs at physiological concentrations in cells unknown
  11. 2025 High

    Structural elucidation of the UBA7 UFD–UBE2L6 interface and determination that UBE2L6~ISG15 exclusively engages HECT E3s while UBE2L6~Ub engages RBR E3s resolved how a single E2 achieves pathway-specific E3 selectivity through modifier-dependent conformational states.

    Evidence NMR solution structure of UBA7 UFD with mutagenesis; structural and biochemical trans-thiolation assays comparing ISG15- and Ub-charged UBE2L6 with HECT, RING, and RBR E3s

    PMID:41773046 PMID:bio_10.1101_2025.09.26.678755

    Open questions at the time
    • Full structure of the UBE2L6~ISG15–HERC5 ternary complex not yet available
    • Whether other HECT E3s beyond HERC5 are engaged by ISG15-charged UBE2L6 in vivo not systematically tested

Open questions

Synthesis pass · forward-looking unresolved questions
  • Major open questions include how UBE2L6 dimerization is regulated in vivo, the full catalog of E3 partners for its ISGylation function beyond HERC5, and whether its dual specificity is temporally or spatially segregated within cells.
  • No live-cell imaging or proximity labeling studies mapping UBE2L6's subcellular activity dynamics
  • Comprehensive E3 interactome for the ISG15 pathway not established
  • Role of post-translational modifications on UBE2L6 itself in switching between ubiquitin and ISG15 pathways not explored

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140096 catalytic activity, acting on a protein 5 GO:0016740 transferase activity 4
Localization
GO:0005634 nucleus 2 GO:0005829 cytosol 1
Pathway
R-HSA-392499 Metabolism of proteins 6 R-HSA-168256 Immune System 4 R-HSA-1430728 Metabolism 1 R-HSA-1640170 Cell Cycle 1 R-HSA-73894 DNA Repair 1
Partners
HERC5HHARIISG15RNF125SIAH1STAT1UBA7UBR4
Complex memberships
CRL4-Cdt2

Evidence

Reading pass · 17 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2004 UBE2L6 (UbcH8) was identified as the E2 conjugating enzyme for ISG15 in addition to its role in ubiquitin conjugation. Purification and in vitro assays demonstrated that UbcH8 forms a thioester with ISG15 and transfers it to substrates, and RNAi knockdown confirmed it is a major E2 for ISG15 conjugation in vivo. A UbcH8-competent ubiquitin ligase was shown to conjugate ISG15 to a specific target in vitro. Biochemical purification, in vitro E2 charging assays, RNA interference knockdown Proceedings of the National Academy of Sciences of the United States of America High 15131269
1999 UBE2L6 (UbcH8) physically interacts with RING finger/IBR domain-containing proteins HHARI and H7-AP1. In vitro binding studies showed the N-terminal RING finger of HHARI and the IBR domain of both proteins mediate interaction with UbcH8, and this binding is specific (UbcH5 and UbcH1 do not bind), linking UBE2L6 to RING/IBR-type E3 ligases. Yeast two-hybrid screen, in vitro binding assays The Journal of biological chemistry Medium 10521492
2009 The NMR structure of the UbcH8–ubiquitin covalent complex (disulfide bond mimicking the thioester) was determined. Ubiquitin contacts the linker region preceding the α5 helix and residues near the catalytic site of UbcH8, defining a unique ubiquitin-interaction surface distinct from other E2 enzymes, while still permitting E1 and E3 interactions. NMR spectroscopy, chemical shift perturbation, cross-saturation, HADDOCK molecular docking Biochemistry High 19928833
2010 UBE2L6 (UBCH8) physically interacts with the E3 ubiquitin ligase SIAH1 and together targets constitutively active FLT3-ITD for K48-linked polyubiquitination and proteasomal degradation. Tyrosine phosphorylation of FLT3 was identified as a determinant for its degradation by this complex. Gain- and loss-of-function experiments confirmed the requirement for UBCH8. Co-immunoprecipitation, gain/loss-of-function (overexpression and siRNA knockdown), proteasome inhibitor experiments Leukemia Medium 20508617
2007 UBE2L6 (UbcH8) mediates both ubiquitin and ISG15 conjugation to RIG-I. UbcH8 suppresses RIG-I ubiquitination by the E3 ligase RNF125, and this suppression is relieved by ISG15 expression. Conversely, RNF125 suppresses ISG15 conjugation to RIG-I. UbcH8 and ISG15 function as regulators of RNF125 E3 ligase activity toward RIG-I. Ectopic expression, co-immunoprecipitation, functional reporter assays Molecular immunology Medium 17719635
2011 UBE2L6 (UBCH8) is the E2 ubiquitin-conjugating enzyme utilized by the CRL4Cdt2 E3 ubiquitin ligase complex to ubiquitylate and degrade p21 (both during normal cell cycle and after UV irradiation), Set8, and to monoubiquitylate PCNA. siRNA depletion of UBCH8 increases p21 protein levels, delays S phase entry, and suppresses the DNA damage response. A different E2 (UBE2G1/G2) handles Cdt1 degradation by the same E3, demonstrating substrate-selective E2 usage. Proteomic analysis (Co-IP/MS), RNAi screening, siRNA knockdown with cell cycle and DNA damage phenotypic readouts Molecular and cellular biology High 21628527
2017 Depletion of UBE2L6 by siRNA in esophageal cancer cells results in enhanced endogenous autophagic flux (measured by LC3II expression and Cyto-ID staining), identifying UBE2L6 as a suppressor of autophagy. siRNA knockdown, LC3II Western blotting, Cyto-ID staining Oncotarget Medium 28186990
2020 UBE2L6 promotes ATGL (adipose triglyceride lipase) ubiquitylation and proteasomal degradation, thereby negatively regulating ATGL-mediated lipolysis. Adipose-specific Ube2l6 knockout mice showed increased ATGL protein levels and enhanced lipolysis, reduced fat mass, and protection from diet-induced obesity, insulin resistance, and hepatic steatosis. Adipose-specific conditional knockout mouse model, protein ubiquitylation assays, metabolic phenotyping Journal of pharmacological sciences Medium 33712284
2020 UBE2L6 inhibits ATRA-induced ISGylation and leukemic cell differentiation. shRNA-mediated UBE2L6 depletion in APL (NB4) cells attenuated ATRA-induced ISG15 conjugation and impeded granulocytic differentiation, placing UBE2L6 as a required catalytic component for ISGylation in this differentiation pathway. shRNA knockdown, ISG15 conjugation assays (Western blot for ISG15 conjugates), differentiation assays Molecular oncology Medium 31820845
2023 UBE2L6 cooperates with the E3 ligase UBR4 to ubiquitylate EZH2 at lysine 381, leading to EZH2 proteasomal degradation in melanoma cells. UHRF1-mediated CpG methylation of the UBE2L6 promoter downregulates UBE2L6 expression in low-pigmented melanoma cells, thereby stabilizing EZH2 and maintaining a low-pigmented cell state. Biochemical assays (Co-IP, ubiquitination assay identifying K381 site), siRNA knockdown, animal xenograft studies, promoter methylation analysis Oncogene Medium 36906655
2023 Ube2L6 promotes STAT1 ISGylation (via ISG15), which activates STAT1 and drives M1 macrophage polarization in obese mice. Adipose-specific Ube2L6 knockout reduced M1 polarization and macrophage infiltration, and Co-IP confirmed UBE2L6 interaction with STAT1. Adipose-specific knockout mouse model, co-immunoprecipitation, flow cytometry, RT-qPCR, ELISA Obesity facts Medium 37820603
2024 UBE2L6 exists in a concentration-dependent monomer-dimer equilibrium in solution. SAXS revealed a dimeric structure dissociable by N-terminal GST fusion, and NMR identified a backside dimerization interface with dimer-induced conformational dynamics at E1 and E3 interfaces, suggesting dimerization may regulate E1/E3 binding. SAXS, NMR spectroscopy (chemical shift perturbation, 15N relaxation), GST-fusion dissociation ACS omega Medium 39346869
2024 The cryo-EM structure of the UBA7•UBE2L6 disulfide complex was determined, revealing three factors governing ISG15 conjugation specificity: strong binding affinity/specificity of UBA7 for UBE2L6 over UBE2L3, conformational differences in the catalytic cysteine capping loop (CCL), and increased thiolate/thiol ratios at catalytic cysteines. Modification of any factor impairs complex activation and ISG15 transfer. Cryo-EM structural determination, mutagenesis, biochemical binding/activity assays bioRxivpreprint Medium bio_10.1101_2024.11.07.622398
2025 The NMR solution structure of the Uba7 ubiquitin-fold domain (UFD) was determined and its interaction surface with UbcH8 was mapped. Residue C996 is essential for UFD structural integrity and UbcH8 binding. The acidic loop architecture (residues 996–1008) is a critical determinant for efficient UbcH8 recruitment, and binding induces conformational dynamics at the E1-E2 interface. Solution NMR, 15N relaxation measurements, site-directed mutagenesis, NMR chemical shift perturbation Biochemistry High 41773046
2025 UBE2L6∼ISG15 specifically engages HECT-family E3 ligases (particularly HERC5) but is inactive with RING or RBR E3 ligases, whereas UBE2L6∼Ub preferentially engages RBR E3s. Structural and biochemical studies revealed that a unique closed conformation of UBE2L6∼ISG15 enables HERC5-mediated trans-thiolation. HERC5's C-lobe specifically recognizes donor ISG15 for lysine conjugation. Structural studies, in vitro biochemical trans-thiolation assays, comparison of E3 specificity for ISG15 vs. ubiquitin-charged UBE2L6 bioRxivpreprint Medium bio_10.1101_2025.09.26.678755
2006 UBE2L6 (UbcH8) physically interacts with the MINT (Msx2-interacting nuclear target protein) transcription factor via MINT's C-terminal SPOC domain. Interaction was confirmed by yeast two-hybrid, GST pull-down, and co-immunoprecipitation in mammalian cells. MINT-mediated transcription suppression was sensitive to the proteasome inhibitor MG132, linking UBE2L6 to MINT-mediated transcriptional regulation via the ubiquitin-proteasome pathway. Yeast two-hybrid, GST pull-down, co-immunoprecipitation, mammalian two-hybrid, reporter assay with MG132 Molecular and cellular biochemistry Medium 16583136
2024 p53 promotes FoxO3a ubiquitination and degradation in retinal endothelial cells by increasing expression of the E2 ubiquitin-conjugating enzyme UBE2L6, thereby accelerating cellular senescence in a model of diabetic retinopathy. RNA sequencing, scRNA-seq, p53 inhibition experiments, Western blotting for ubiquitination and senescence markers Experimental gerontology Low 38437929

Source papers

Stage 0 corpus · 30 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2004 The UbcH8 ubiquitin E2 enzyme is also the E2 enzyme for ISG15, an IFN-alpha/beta-induced ubiquitin-like protein. Proceedings of the National Academy of Sciences of the United States of America 268 15131269
1999 The ubiquitin-conjugating enzymes UbcH7 and UbcH8 interact with RING finger/IBR motif-containing domains of HHARI and H7-AP1. The Journal of biological chemistry 101 10521492
2010 Ubiquitin conjugase UBCH8 targets active FMS-like tyrosine kinase 3 for proteasomal degradation. Leukemia 60 20508617
2007 UbcH8 regulates ubiquitin and ISG15 conjugation to RIG-I. Molecular immunology 49 17719635
2009 The structure of the UbcH8-ubiquitin complex shows a unique ubiquitin interaction site. Biochemistry 48 19928833
2011 Selective ubiquitylation of p21 and Cdt1 by UBCH8 and UBE2G ubiquitin-conjugating enzymes via the CRL4Cdt2 ubiquitin ligase complex. Molecular and cellular biology 43 21628527
2017 UBE2L6/UBCH8 and ISG15 attenuate autophagy in esophageal cancer cells. Oncotarget 35 28186990
2020 E2 ubiquitin-conjugating enzyme UBE2L6 promotes Senecavirus A proliferation by stabilizing the viral RNA polymerase. PLoS pathogens 34 33104725
2018 UHRF1 epigenetically down-regulates UbcH8 to inhibit apoptosis in cervical cancer cells. Cell cycle (Georgetown, Tex.) 28 29157076
2016 Honokiol induces proteasomal degradation of AML1-ETO oncoprotein via increasing ubiquitin conjugase UbcH8 expression in leukemia. Biochemical pharmacology 22 28043811
2005 Down-regulation of UCRP and UBE2L6 in BRCA2 knocked-down human breast cells. Biochemical and biophysical research communications 20 15670748
2024 p53 accelerates endothelial cell senescence in diabetic retinopathy by enhancing FoxO3a ubiquitylation and degradation via UBE2L6. Experimental gerontology 17 38437929
2023 UHRF1/UBE2L6/UBR4-mediated ubiquitination regulates EZH2 abundance and thereby melanocytic differentiation phenotypes in melanoma. Oncogene 16 36906655
2020 Inhibition of UBE2L6 attenuates ISGylation and impedes ATRA-induced differentiation of leukemic cells. Molecular oncology 16 31820845
2013 Identification of a loss-of-function mutation in Ube2l6 associated with obesity resistance. Diabetes 16 23557705
2019 Up-regulation of interferon-stimulated gene 15 and its conjugation machinery, UbE1L and UbcH8 expression by tumor necrosis factor-α through p38 MAPK and JNK signaling pathways in human lung carcinoma. Molecular and cellular biochemistry 15 31428903
2023 Ube2L6 Promotes M1 Macrophage Polarization in High-Fat Diet-Fed Obese Mice via ISGylation of STAT1 to Trigger STAT1 Activation. Obesity facts 13 37820603
2020 UBE2L6 is Involved in Cisplatin Resistance by Regulating the Transcription of ABCB6. Anti-cancer agents in medicinal chemistry 12 32329696
2020 Adipose-specific knockout of ubiquitin-conjugating enzyme E2L6 (Ube2l6) reduces diet-induced obesity, insulin resistance, and hepatic steatosis. Journal of pharmacological sciences 10 33712284
2018 Furosine Induced Apoptosis by the Regulation of STAT1/STAT2 and UBA7/UBE2L6 Genes in HepG2 Cells. International journal of molecular sciences 10 29857509
2024 MX1 and UBE2L6 are potential metaflammation gene targets in both diabetes and atherosclerosis. PeerJ 9 38406276
2021 Homoharringtonine Synergized with Gilteritinib Results in the Downregulation of Myeloid Cell Leukemia-1 by Upregulating UBE2L6 in FLT3-ITD-Mutant Acute Myeloid (Leukemia) Cell Lines. Journal of oncology 8 34594375
2000 Genomic organization of the human ubiquitin-conjugating enzyme gene, UBE2L6 on chromosome 11q12. Cytogenetics and cell genetics 7 10894956
2006 The Spen homolog Msx2-interacting nuclear target protein interacts with the E2 ubiquitin-conjugating enzyme UbcH8. Molecular and cellular biochemistry 6 16583136
2023 Association of UBE2L6 and ABCB6 Expression With Platinum Resistance in Serous Ovarian Carcinoma. Anticancer research 4 37500176
2025 Decursin induces FLT3-ITD acute myeloid leukemia cell apoptosis by increasing the expression of the ubiquitin-conjugase UBE2L6. Cell communication and signaling : CCS 3 40176110
2025 Porcine reproductive and respiratory syndrome virus NSP5 exploited UBE2L6 to promote viral replication via antagonising host RLRs and ISGylation. Veterinary research 3 40611336
2026 Dynamic Hotspots in the Uba7 Ubiquitin-Fold Domain Direct UbcH8 Recognition. Biochemistry 0 41773046
2024 Characterizing the monomer-dimer equilibrium of UbcH8/Ube2L6: A combined SAXS and NMR study. bioRxiv : the preprint server for biology 0 37090523
2024 Characterizing the Monomer-Dimer Equilibrium of UbcH8/Ube2L6: A Combined SAXS and NMR Study. ACS omega 0 39346869