| 2007 |
UBE1L2 (UBA6) is a second human ubiquitin-activating E1 enzyme that forms a covalent thioester with ubiquitin in vitro and in vivo in an ATP-dependent manner, and can transfer ubiquitin to the E2 enzyme UbcH5b, supporting subsequent ubiquitylation of p53 by MDM2 and autoubiquitylation of E3 ligases HectH9 and E6-AP. |
In vitro ubiquitylation assay, in vivo thioester formation, in vitro polyubiquitylation with recombinant proteins |
The Journal of biological chemistry |
High |
17580310
|
| 2008 |
UBA6 activates not only ubiquitin but also the ubiquitin-like modifier FAT10, and uses a different spectrum of E2 conjugating enzymes compared to UBE1, establishing UBA6 as a bispecific E1 enzyme with its own dedicated E2 partner USE1. |
Biochemical characterization, E1-E2 specificity assays |
Trends in biochemical sciences |
Medium |
18353650
|
| 2012 |
Uba6 undergoes a three-step activation process (adenylation, thioester formation, transthiolation) for both ubiquitin and FAT10, forming a ternary complex with both substrates. FAT10 binds Uba6 with higher affinity than ubiquitin but demonstrates lower catalytic activity in ATP-PPi exchange and E1-E2 transthiolation assays. A mechanism-based inhibitor (Compound 1) forms covalent adducts with both ubiquitin and FAT10 on Uba6. |
Biochemical assays, pre-steady state kinetics, mechanism-based inhibitor, biophysical binding measurements |
The Journal of biological chemistry |
High |
22427669
|
| 2013 |
The Uba6–Use1 ubiquitin transfer cascade is required for mouse embryonic development independently of the canonical Uba1 pathway. In neuronal Uba6-knockout mice, loss of Uba6 results in abnormal hippocampal and amygdala neuron patterning, decreased dendritic spine density, and elevated levels of Ube3a (E6-AP) and Shank3 in the amygdala. Uba6 and Use1 promote proteasomal turnover of Ube3a in MEFs and catalyze Ube3a ubiquitylation in vitro, acting in a spatially distinct manner from the Uba1–UbcH7 pathway. |
Neuronal-specific Uba6 knockout mouse, in vitro ubiquitylation assay, MEF proteasomal turnover assay, immunofluorescence, behavioral studies |
Molecular cell |
High |
23499007
|
| 2014 |
USE1 (the dedicated E2 of UBA6) undergoes self-FAT10ylation in cis, primarily at Lys323, which accelerates its proteasomal degradation and thereby limits overall FAT10ylation levels as a negative feedback mechanism. The USE1-FAT10 conjugate retains catalytic activity and can still form thioesters with both FAT10 and ubiquitin. |
Mass spectrometry, site-directed mutagenesis, co-immunoprecipitation, proteasome inhibitor assays, in vitro thioester assay |
The FEBS journal |
Medium |
24528925
|
| 2016 |
LMO2 interacts with the C-terminal ubiquitin fold domain (UFD) of UBA6, which is the domain that recruits the E2 USE1. This interaction blocks UBA6–USE1 binding and reduces overall cellular FAT10ylation levels, including FAT10ylation and degradation of the substrate p62. |
Co-immunoprecipitation, domain mapping, FAT10ylation assays, pulldown |
Biochemical and biophysical research communications |
Medium |
27569286
|
| 2017 |
UBA6 deficiency in MCF-10A mammary epithelial cells leads to failure in cell cycle arrest upon matrix detachment and spontaneous epithelial-mesenchymal transition (EMT). The Rho-GTPase CDC42 is identified as a specific target of UBA6-initiated ubiquitination, and a CDC42 inhibitor rescues UBA6-deficient cells from the EMT phenotype. |
shRNA knockdown, EMT assays, pharmacological inhibition of CDC42, cell biology assays |
Oncotarget |
Medium |
29152096
|
| 2019 |
UBA6 and BIRC6 cooperate to monoubiquitinate LC3B, targeting it for proteasomal degradation. Knockout of UBA6 or BIRC6 increases autophagic flux under nutrient deprivation or protein synthesis inhibition, and decreases aggresome-like induced structures and α-synuclein aggregates, demonstrating that the UBA6–BIRC6 axis negatively regulates autophagy by limiting LC3B availability. |
Whole-genome CRISPR/Cas9 knockout screen, fluorescent LC3B reporter, KO cell lines, autophagic flux assays, neuronal aggregate assays |
eLife |
High |
31692446
|
| 2020 |
UBA6 (together with UBE1) regulates ubiquitination and expression of the cardiac sodium channel Nav1.5 at lysine residues K590 and K591, acting through the E2 enzyme UBC9. Overexpression of UBA6 increases Nav1.5 ubiquitination and decreases Nav1.5 expression and sodium current density, while knockdown has the opposite effect. |
Western blot, patch-clamp electrophysiology, overexpression/knockdown, site-directed mutagenesis (K590A/K591A), neonatal cardiomyocytes |
The Biochemical journal |
Medium |
32315024
|
| 2021 |
UBA6 regulates IFN-γ production in T cells by promoting IκBα degradation, thereby increasing NF-κB p65 activation. T cell-specific UBA6-deficient mice show elevated IFN-γ production from CD4 and CD8 T cells, and transfer of UBA6-deficient T cells exacerbates multi-organ inflammation. |
T cell-specific conditional knockout mice, cytokine production assays, NF-κB pathway analysis, adoptive transfer experiments |
Cells |
Medium |
35011668
|
| 2022 |
UBA6 and the adaptor protein NDFIP1 are required for hepcidin-induced ubiquitination and degradation of ferroportin. siRNA-mediated depletion of UBA6 prevents BMP6- and hepcidin-induced ferroportin degradation in vitro, and AAV-mediated silencing of Ndfip1 in mouse liver increases hepatic ferroportin and circulating iron. |
siRNA screen (88 ubiquitin pathway components), FPN-GFP reporter cell line, in vivo AAV silencing in mice, iron measurements |
Haematologica |
Medium |
34320783
|
| 2022 |
Crystal structures of human Uba6/ubiquitin complex reveal two conformational states: an open conformation configured for adenylation and a closed conformation for thioester bond formation. An inositol hexakisphosphate (InsP6) molecule binds to a previously unidentified allosteric site on Uba6 and inhibits Uba6 activity by altering interconversion between the open and closed conformations while enhancing enzyme stability. |
X-ray crystallography, biochemical activity assays, biophysical binding measurements |
Nature communications |
High |
35986001
|
| 2024 |
UBA6 recognizes a polyalanine stretch within its cognate E2 USE1. Polyalanine expansion mutations in USE1 reduce ubiquitin transfer from UBA6 to USE1 and decrease polyubiquitination and degradation of Ube3a (E6-AP). Proteins with polyalanine expansion mutations in disease states compete for UBA6–USE1 interaction, altering E6AP levels and Arc synaptic protein levels in neurons. |
In vitro ubiquitin transfer assays, iPSC-derived neurons from patients, mouse primary neurons, UBA6 overexpression rescue experiments |
The EMBO journal |
High |
38177505
|
| 2025 |
BIRC6 is a UBA6-exclusive E2 enzyme that gains priority over all other UBA6-competent E2s by engaging the UBA6 ubiquitin fold domain (UFD) with exceptionally high affinity, modulated by the UBA6 Cys-Cap loop. A bespoke thioester switch mechanism disengages BIRC6 upon receiving ubiquitin, preventing inhibition of UBA6 despite BIRC6's priority. UBA6 achieves broader E2 specificity through coordinated contributions of both UFD and SCCH domains. |
Structural biology (cryo-EM capturing UBA6-BIRC6 complexes), biochemical E1-E2 specificity assays, mutagenesis |
Nature structural & molecular biology |
High |
41350950
|
| 2026 |
Cryo-EM structures of UBA6-E2 complexes at the thioester-transfer step with either FAT10 or ubiquitin reveal that UBA6 achieves E2 specificity through coordinated contributions of both the UFD and SCCH domains (contrasting with UFD-dominated selectivity of UBA1). An InsP6-binding site unique to UBA6 stabilizes an expanded SCCH cleft that pre-organizes the enzyme for selective engagement of UBA6-specific E2s, identifying InsP6 as a cofactor shaping specificity. |
Chemical trapping, cryo-EM (four UBA6-E2 complex structures), biochemical assays |
Nature communications |
High |
41764162
|
| 2025 |
In UBA1M41V (VEXAS syndrome) human cells, UBA6 compensates for UBA1 dysfunction, creating an acquired dependency on UBA6. Genetic (shRNA) or pharmacological (phytic acid/InsP6) inhibition of UBA6 preferentially impairs growth and colony formation of UBA1M41V cells while sparing wild-type cells. |
Engineered human cell model (THP1 UBA1M41V), shRNA knockdown, pharmacological inhibition with phytic acid, competition assays, proteomic analysis |
Leukemia |
Medium |
40588566
|