Affinage

UBA3

NEDD8-activating enzyme E1 catalytic subunit · UniProt Q8TBC4

Length
463 aa
Mass
51.9 kDa
Annotated
2026-06-10
14 papers in source corpus 10 papers cited in narrative 10 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 7/7 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

UBA3 is the catalytic subunit of the heterodimeric NEDD8-activating enzyme (E1), partnering with APPBP1/NAE1 to selectively activate the ubiquitin-like protein NEDD8 and initiate the neddylation cascade (PMID:14690597, PMID:12740388). Activation proceeds by a pseudo-ordered mechanism in which ATP binds first and NEDD8 second, generating a NEDD8-adenylate and a UBA3-NEDD8 thioester intermediate that is then transthiolated onto the E2 enzyme HsUbc12/UBE2M (PMID:12740388). Substrate selectivity is enforced both by a single conserved arginine "selectivity gate" in the APPBP1-UBA3 interface that excludes ubiquitin and by NEDD8 residue Ala72, mutation of which (Ub R72L) confers E1 activity on ubiquitin (PMID:14690597, PMID:12740388). Although the enzyme is heterodimeric, UBA3 alone is sufficient for NEDD8 activation, with APPBP1 acting principally as a scaffold that accelerates catalysis (PMID:29973603); the C-terminal ubiquitin-like β-grasp domain of UBA3 engages the E2 through a conformationally dynamic surface that adopts a defined kinked helix upon complex formation (PMID:22821745). Beyond NEDD8, UBA3 (with NAE1 and UBE2M) also serves as the E1 for URM1 conjugation (urmylation), a specificity captured by activity-based probes under normal and oxidative-stress conditions (PMID:42056084). UBA3-driven neddylation modulates oncogenic signaling: it neddylates p53 to block its K373 acetylation and suppress p21/PTEN transcription (PMID:37668436), and supports NF-κB signaling by limiting IκBα phosphorylation (PMID:37656220). UBA3 is the pharmacological target of NAE inhibitors, and point mutations (I310N, Y352H) that alter ATP and NEDD8 affinity confer resistance to MLN4924 (PMID:24691136).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 2003 High

    Established the structural and kinetic basis for how UBA3-APPBP1 activates NEDD8 and discriminates it from ubiquitin, defining the first mechanistic picture of the NEDD8 E1.

    Evidence X-ray crystallography of the APPBP1-UBA3-NEDD8-ATP quaternary complex with mutational analysis, plus in vitro enzyme kinetics, isotope exchange, and transthiolation assays

    PMID:12740388 PMID:14690597

    Open questions at the time
    • Did not resolve how the E2 (Ubc12) is recruited at atomic resolution
    • Selectivity gate defined biochemically; in-cell consequences of gate mutation not tested
    • No structure of the thioester intermediate captured
  2. 2003 Medium

    Identified physical and genetic regulators of Uba3 in fission yeast, raising the possibility of negative regulation of the NEDD8 pathway by binding partners.

    Evidence Two-hybrid screen and overexpression/genetic epistasis with a ned8-ts mutant in fission yeast

    PMID:14623327

    Open questions at the time
    • Mechanism of inhibition by But1/But2 not biochemically defined
    • Human orthologs and relevance not established
    • Indirect inhibitory role inferred from overexpression phenotypes
  3. 2012 Medium

    Resolved that the E2-binding β-grasp domain of UBA3 is conformationally dynamic, explaining how the static crystal interface accommodates E2 engagement.

    Evidence NMR spectroscopy of the isolated Uba3 β-grasp domain compared with crystal structures

    PMID:22821745

    Open questions at the time
    • Isolated domain studied out of full-length enzyme context
    • No functional mutagenesis linking dynamics to catalysis
    • Single lab, single method
  4. 2014 Medium

    Demonstrated that UBA3 is the direct target of NAE inhibitors and that defined active-site mutations rewire ATP/NEDD8 affinity to confer drug resistance, clarifying the enzyme's inhibitor pharmacology.

    Evidence Selection of MLN4924-resistant cell lines, sequencing, and kinetic characterization of mutant enzymes

    PMID:24691136

    Open questions at the time
    • Resistance mutations not validated structurally
    • Clinical relevance of these specific mutations not addressed
    • Single lab
  5. 2018 Medium

    Dissected the contribution of each E1 subunit, showing UBA3 alone catalyzes NEDD8 activation while APPBP1 acts as a rate-accelerating scaffold, distinguishing NEDD8 E1 from SUMO E1.

    Evidence Quantitative FRET assays with individual subunits supported by computational electrostatic analysis

    PMID:29973603

    Open questions at the time
    • Key claim rests on a single FRET-based method
    • Physiological role of UBA3-only activation in cells not shown
    • Rate enhancement by APPBP1 not quantified at all reaction steps
  6. 2023 Medium

    Connected UBA3 neddylation activity to oncogenic signaling, showing neddylation suppresses p53 acetylation/activity and promotes NF-κB-driven cytokine production in lung cancer.

    Evidence Overexpression and knockdown in lung cancer/LUAD cells with co-IP, acetylation and promoter assays, mRNA-seq, and functional migration/invasion assays

    PMID:37656220 PMID:37668436

    Open questions at the time
    • p53 and IκBα effects not reconstituted in vitro
    • Whether p53 is a direct UBA3 neddylation substrate vs. indirect not fully resolved
    • NF-κB pathway link is transcriptomic/correlative without direct biochemical step
  7. 2024 Low

    Extended UBA3's tumor-promoting role to cholangiocarcinoma via an ANXA2/MAPK axis and identified bufalin as a UBA3-targeting inhibitor.

    Evidence shRNA knockdown in ICC cell lines with mechanistic and inhibitor studies

    PMID:38298057

    Open questions at the time
    • Pathway placement is indirect with limited orthogonal validation
    • Direct UBA3-ANXA2 biochemical relationship not established
    • Single lab
  8. 2026 Medium

    Revealed an expanded substrate specificity in which NAE1/UBA3 and UBE2M also act as the E1/E2 for URM1 conjugation (urmylation), linking the enzyme to oxidative-stress signaling and chemosensitization.

    Evidence Activity-based URM1 probe capture with proteomics, cell-based validation, and pevonedistat/cisplatin synergy assays in liver cancer cells

    PMID:42056084

    Open questions at the time
    • Kinetics of URM1 activation by UBA3 not characterized
    • Structural basis for dual NEDD8/URM1 selectivity unknown
    • Physiological URM1 substrates not fully enumerated

Open questions

Synthesis pass · forward-looking unresolved questions
  • How UBA3 partitions catalytic capacity between NEDD8 and URM1 conjugation, and how this dual activity is regulated in vivo, remains unresolved.
  • No structural or kinetic comparison of NEDD8 vs URM1 activation by UBA3
  • Regulatory inputs controlling substrate choice unknown
  • In vivo physiological significance of urmylation by UBA3 not defined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0016874 ligase activity 3 GO:0140657 ATP-dependent activity 2 GO:0140096 catalytic activity, acting on a protein 1
Pathway
R-HSA-392499 Metabolism of proteins 3 R-HSA-162582 Signal Transduction 2 R-HSA-1643685 Disease 2
Complex memberships
NEDD8-activating enzyme (NAE/E1) heterodimer (UBA3-APPBP1/NAE1)

Evidence

Reading pass · 10 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2003 Crystal structure of the 120 kDa quaternary complex of human APPBP1-UBA3 (heterodimeric E1), NEDD8, and ATP was solved, revealing a bipartite interface for selective NEDD8 recruitment involving a domain common to all ubl-activating enzymes plus eukaryotic E1-specific sequences. A single conserved arginine in APPBP1-UBA3 acts as a selectivity gate preventing misactivation of ubiquitin by NEDD8's E1. X-ray crystallography of quaternary complex + mutational analysis modeling ubiquitin into NEDD8 binding site Molecular cell High 14690597
2003 Human APPBP1-UBA3 catalyzes NEDD8 activation via a pseudo-ordered mechanism (ATP leading, NEDD8 trailing substrate), forming a stable ternary complex of NEDD8-adenylate and Uba3-NEDD8 thioester intermediate, and then transferring NEDD8 to HsUbc12 (kcat = 3.5 s⁻¹). Alanine 72 of NEDD8 is a critical specificity determinant for APPBP1-UBA3 binding, since the Ub(R72L) mutant can serve as substrate. Wild-type ubiquitin fails to support activation or HsUbc12 transthiolation. In vitro enzyme kinetics with radiolabeled ATP and 125I-NEDD8, isotope exchange, transthiolation assays, mutagenesis The Journal of biological chemistry High 12740388
2003 In fission yeast, But1 and But2 proteins physically bind to Uba3 (the catalytic subunit of NEDD8 E1). But1 is a nuclear protein and its overexpression causes cell elongation (a phenotype of NEDD8 pathway defective mutants); overexpression of but1+ in a ned8-ts mutant was deleterious at permissive temperatures, suggesting But1 has an inhibitory role in the NEDD8 pathway. Two-hybrid screen, overexpression phenotype analysis, genetic interaction with ned8-ts mutant Biochemical and biophysical research communications Medium 14623327
2012 The C-terminal ubiquitin-like β-grasp domain of human Uba3 (Uba3-βGD) is independently folded in solution and its E2-binding surface undergoes conformational exchange between multiple substates (residues absent from NMR spectrum in free form, adopting a kinked α-helix when complexed with E2), analogous to the E2-binding surface of SUMO E1. NMR spectroscopy of isolated Uba3 β-grasp domain, comparison with crystal structures Proteins Medium 22821745
2014 UBA3 point mutations I310N (in K562 cells) and Y352H (in U937 cells) confer resistance to the NAE inhibitor MLN4924 by increasing the enzyme's affinity for ATP while decreasing its affinity for NEDD8, thereby reducing MLN4924 potency while preserving sufficient NAE activity for cell survival. Selection of resistant cell lines by chronic MLN4924 exposure, sequencing, biochemical analyses of mutant enzyme kinetics PloS one Medium 24691136
2018 Using quantitative FRET, UBA3 alone (without APPBP1) is sufficient for NEDD8 activation, whereas APPBP1 functions mainly as a scaffold to accelerate the reaction rate. This contrasts with SUMO E1, where both heterodimer subunits are required for activation. Quantitative FRET assays with individual subunits, aided by AESOP computational electrostatic analysis Scientific reports Medium 29973603
2023 UBE1C (UBA3)-mediated neddylation of p53 inhibits p53 acetylation at K373, suppresses p53 transcriptional activity, and reduces expression of p53 downstream targets p21 and PTEN. Overexpression of UBE1C/UBA3 and NEDD8 promotes lung cancer cell migration, invasion, and proliferation. Overexpression of UBE1C and NEDD8 in lung cancer cells, co-IP/Western blot for p53 neddylation and acetylation, promoter activity assays, functional cell assays FASEB journal Medium 37668436
2023 UBA3-dependent neddylation in lung adenocarcinoma cells promotes NF-κB signaling by preventing IκBα phosphorylation/accumulation; blocking UBA3 increases p-IκBα and reduces gene expression of tumor-derived cytokines (CCL2, CXCL1, CXCL2, CSF1, CSF2, IL-6, IL-1B), and decreases recruitment of immunosuppressive cells (TAMs, pDCs, Th2, Tregs). mRNA sequencing, functional enrichment, Western blotting, real-time PCR after UBA3 knockdown in LUAD cells Medical oncology Low 37656220
2024 UBA3 promotes intrahepatic cholangiocarcinoma proliferation, invasion, and migration by affecting ANXA2 through the MAPK signaling pathway; knockdown of UBA3 inhibits these processes. Bufalin was identified as a targeting inhibitor of UBA3 that suppresses ICC development through this pathway. shRNA knockdown of UBA3 in ICC cell lines, mechanistic experiments linking UBA3 to ANXA2/MAPK, bufalin inhibitor studies Acta biochimica et biophysica Sinica Low 38298057
2026 NAE1/UBA3 and UBE2M function as E1 and E2 enzymes, respectively, for the urmylation (URM1 conjugation) pathway in human cells under normal and oxidative stress conditions. An activity-based URM1 probe covalently captured cysteine enzymes in the URM1 signaling pathway, identifying this new substrate specificity. Pharmacologic inhibition of NAE1/UBA3 by pevonedistat blocks protein urmylation and exhibits synergy with cisplatin in killing liver cancer cells. Activity-based URM1 probe capture, proteomic characterization, cell-based validation, pharmacologic perturbation Nature communications Medium 42056084

Source papers

Stage 0 corpus · 14 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2003 The structure of the APPBP1-UBA3-NEDD8-ATP complex reveals the basis for selective ubiquitin-like protein activation by an E1. Molecular cell 242 14690597
2003 Conservation in the mechanism of Nedd8 activation by the human AppBp1-Uba3 heterodimer. The Journal of biological chemistry 110 12740388
2014 Mutations in UBA3 confer resistance to the NEDD8-activating enzyme inhibitor MLN4924 in human leukemic cells. PloS one 36 24691136
2005 Expression, purification, and characterization of the E1 for human NEDD8, the heterodimeric APPBP1-UBA3 complex. Methods in enzymology 29 16275315
2024 UBA3 promotes the occurrence and metastasis of intrahepatic cholangiocarcinoma through MAPK signaling pathway. Acta biochimica et biophysica Sinica 18 38298057
2018 Dissecting Distinct Roles of NEDDylation E1 Ligase Heterodimer APPBP1 and UBA3 Reveals Potential Evolution Process for Activation of Ubiquitin-related Pathways. Scientific reports 16 29973603
2003 But1 and But2 proteins bind to Uba3, a catalytic subunit of E1 for neddylation, in fission yeast. Biochemical and biophysical research communications 9 14623327
2023 UBE1C is upregulated and promotes neddylation of p53 in lung cancer. FASEB journal : official publication of the Federation of American Societies for Experimental Biology 6 37668436
2012 Inhibition of the NEDD8 conjugation pathway by shRNA to UBA3, the subunit of the NEDD8-activating enzyme, suppresses the growth of melanoma cells. Asian Pacific journal of cancer prevention : APJCP 6 22502714
2023 The NEDD8-activating enzyme E1 UBA3 orchestrates the immunosuppressive microenvironment in lung adenocarcinoma via the NF-кB pathway. Medical oncology (Northwood, London, England) 5 37656220
2022 Genetic mapping of Uba3 , a pupal lethal mutation in Drosophila melanogaster. microPublication biology 5 35622528
2012 E2-binding surface on Uba3 β-grasp domain undergoes a conformational transition. Proteins 5 22821745
2026 UBA3 reduction sensitizes cancer cells to NAE inhibitors. Life science alliance 0 42055937
2026 NAE1/UBA3-UBE2M are E1 and E2 enzymes for the URM1 modification. Nature communications 0 42056084

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