{"gene":"UBE4B","run_date":"2026-06-10T10:51:56","timeline":{"discoveries":[{"year":2001,"finding":"The WldS protective gene encodes an N-terminal fragment of UBE4B fused to NMNAT; the chimeric Wld protein localizes predominantly to the nucleus and confers dose-dependent protection against Wallerian degeneration, with NMNAT enzyme activity (not NAD+ content) increased fourfold, indicating an indirect nuclear mechanism of axon protection.","method":"Transgenic mouse expression, subcellular fractionation/localization, enzymatic activity assay","journal":"Nature neuroscience","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct identification of protective gene, localization experiment, enzymatic assay, replicated across multiple transgenic lines","pmids":["11770485"],"is_preprint":false},{"year":2011,"finding":"UBE4B physically interacts with both p53 and Hdm2, promotes p53 polyubiquitination and proteasomal degradation, inhibits p53-dependent transactivation and apoptosis, functioning as an E3/E4 ubiquitin ligase in the p53 regulatory axis.","method":"Co-immunoprecipitation, ubiquitination assay, transactivation reporter assay, xenograft tumor model with UBE4B silencing","journal":"Nature medicine","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — reciprocal Co-IP, in vitro ubiquitination assay, functional rescue experiments, replicated in subsequent studies","pmids":["21317885"],"is_preprint":false},{"year":2013,"finding":"UBE4B is recruited to endosomes upon EGFR activation by binding to Hrs (ESCRT-0 component); UBE4B ubiquitinates EGFR and regulates its endosomal sorting and lysosomal degradation, coordinating with the deubiquitinase USP8.","method":"Co-immunoprecipitation, endosomal fractionation, EGFR degradation assay, siRNA knockdown with functional readout","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, substrate identification, endosomal localization with functional consequence, multiple orthogonal methods in single lab","pmids":["24344129"],"is_preprint":false},{"year":2015,"finding":"Loss of UBE4B (orthologue ufd-2 in C. elegans) synergizes with loss of LSD1 (spr-5) to suppress proteotoxic neurodegeneration; in mammalian cells, loss of UBE4B promotes clearance of misfolded proteins via both proteasomal and autophagic pathways, with p53 identified as a downstream transcriptional effector of this quality control pathway.","method":"C. elegans genetic epistasis (double mutant), mammalian cell knockdown, proteasome/autophagy inhibitor assays","journal":"PLoS biology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis in vivo, mechanistic follow-up in mammalian cells, multiple orthogonal methods","pmids":["25837623"],"is_preprint":false},{"year":2016,"finding":"UBE4B co-immunoprecipitates with phosphorylated p53 at serines 15 and 392; UBE4B promotes degradation of endogenous phospho-p53(S15) and phospho-p53(S392) in response to ionizing radiation, and its affinity for Hdm2 is decreased after DNA damage.","method":"Co-immunoprecipitation with phospho-specific antibodies, IR-induced p53 degradation assay, transactivation reporter assay","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — Co-IP and functional assays in single lab, single study","pmids":["26673821"],"is_preprint":false},{"year":2020,"finding":"UBE4B interacts with and ubiquitinates the HTLV-1 Tax oncoprotein; UBE4B overexpression enhances Tax-induced NF-κB activation, and UBE4B knockdown/knockout attenuates both K48- and K63-linked polyubiquitination of Tax and impairs NF-κB target gene induction.","method":"Yeast two-hybrid screen, co-immunoprecipitation, proximity ligation assay, confocal microscopy, shRNA/CRISPR knockout, NF-κB reporter assay","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Moderate — yeast two-hybrid confirmed by reciprocal Co-IP and PLA, functional validation by KD and KO with orthogonal methods","pmids":["33362245"],"is_preprint":false},{"year":2020,"finding":"UBE4B binds to Hrs (ESCRT-0) on endosomes and ubiquitinates APP; depletion of UBE4B in neurons inhibits APP ubiquitination and internalization into multivesicular body intraluminal vesicles, resulting in increased endosomal Aβ42 generation and secretion.","method":"Co-immunoprecipitation, MVB reconstitution in cortical neurons, siRNA knockdown, ELISA for Aβ42","journal":"Molecular and cellular neurosciences","confidence":"High","confidence_rationale":"Tier 2 / Moderate — substrate identification, endosomal reconstitution, functional knockdown readout, multiple methods in single study","pmids":["32841720"],"is_preprint":false},{"year":2021,"finding":"UBE4B (orthologue CG11070 in Drosophila) promotes ubiquitination and autophagy-lysosome-dependent degradation of Tau; in mammalian neuroblastoma cells UBE4B together with STUB1 (CHIP) increases ubiquitination and degradation of both total and phosphorylated Tau; autophagy inhibitors block this degradation.","method":"Drosophila miRNA screen, overexpression in neuroblastoma cells, ubiquitination assay, autophagy/proteasome inhibitor assays, Tau-BiFC mouse model","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic screen validated in multiple model systems (fly, mammalian cells, mouse), orthogonal inhibitor assays","pmids":["34078905"],"is_preprint":false},{"year":2022,"finding":"UBE4B polyubiquitylates and degrades KLHL22 (an E3 ligase that degrades GATOR1 component DEPDC5); loss of UBE4B causes KLHL22 accumulation and mTOR hyperactivation in neural precursor cells, leading to impaired neurogenesis and seizures; rapamycin rescues neurogenesis defects in Ube4b conditional knockout mice.","method":"Conditional neural knockout mouse, ubiquitination assay, mTOR activity measurement, genetic rescue (KLHL22 suppression), pharmacological rescue (rapamycin)","journal":"Development (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo conditional KO with defined phenotype, substrate identification with ubiquitination assay, genetic and pharmacological rescue","pmids":["36440598"],"is_preprint":false},{"year":2022,"finding":"UBE4B ubiquitinates PP2A, leading to PP2A degradation and consequent AKT activation; this mechanism promotes lung adenocarcinoma cell proliferation, migration, and glycolysis, effects reversed by PP2A overexpression.","method":"Co-immunoprecipitation, ubiquitination assay, overexpression/shRNA in LUAD cells and xenograft","journal":"Pathology, research and practice","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — Co-IP and ubiquitination assay, single lab, limited replication","pmids":["35220170"],"is_preprint":false},{"year":2022,"finding":"SF3B4 interacts with UBE4B (Co-IP); SF3B4 depletion reduces UBE4B levels, which in turn reduces polyubiquitinated p53 levels and causes p53/p21 accumulation and cell cycle arrest in A549 lung cancer cells.","method":"Co-immunoprecipitation, siRNA double knockdown, Western blot, flow cytometry","journal":"Molecules and cells","confidence":"Medium","confidence_rationale":"Tier 2–3 / Weak — Co-IP and knockdown epistasis, single lab, single study","pmids":["35996826"],"is_preprint":false},{"year":2023,"finding":"The SWIB/Hdm2 motif of UBE4B is required for p53 binding; the UBE4B U-box domain does not bind p53 but is essential for p53 degradation and acts in a dominant-negative manner to stabilize p53 when expressed alone; a UBE4B peptide spanning the SWIB/Hdm2 motif blocks p53-UBE4B interaction and activates p53-dependent transactivation and growth inhibition.","method":"Co-immunoprecipitation with domain mutants, transactivation reporter assay, growth inhibition assay, peptide blocking experiment","journal":"Molecular therapy. Nucleic acids","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — domain mutagenesis with functional readout, single lab, single study","pmids":["36865087"],"is_preprint":false},{"year":2023,"finding":"UBE4B interacts with ITCH E3 ligase via ITCH WW domains; ITCH activation leads to ITCH-UBE4B complex formation and recruitment of Ku70 and c-FLIPL, promoting their Lys48/Lys63-branched polyubiquitination and proteasomal degradation; HDAC inhibition induces Ku70 acetylation, releasing c-FLIPL and Bax and enhancing ITCH-UBE4B-mediated polyubiquitination and apoptosis.","method":"Co-immunoprecipitation, Western blot, siRNA knockdown, caspase 8 activation assay","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2–3 / Weak — Co-IP, substrate ubiquitination assay, functional KD readout, single lab","pmids":["37957138"],"is_preprint":false},{"year":2024,"finding":"UBE4B interacts with the RNA-binding protein HuR; UBE4B regulates p27 translation via the cap-independent IRES pathway by modulating the interaction between HuR and the p27 5' UTR IRES, thereby suppressing p27 protein levels independently of ubiquitin-mediated degradation.","method":"Co-immunoprecipitation, RNA pulldown/IRES reporter assay, siRNA knockdown and overexpression, Western blot","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2–3 / Weak — Co-IP plus functional IRES assay, novel non-ubiquitin mechanism, single lab, single study","pmids":["38211530"],"is_preprint":false},{"year":2025,"finding":"ATR-mediated phosphorylation of UBE4B reduces its binding affinity to p53, causing p53 accumulation after DNA damage; the phosphatase Wip1 dephosphorylates UBE4B to restore its p53-binding and degradation activity; inhibition of Wip1 increases UBE4B phosphorylation and further accumulates p53.","method":"Co-immunoprecipitation, kinase inhibitor assays, Wip1 inhibition, phosphorylation-mimetic mutants, Western blot","journal":"Cell death discovery","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — Co-IP with PTM analysis, pharmacological and genetic modulation, single lab study","pmids":["40175346"],"is_preprint":false},{"year":2025,"finding":"UBE4B directly binds DHO (dihydroorotic acid) and subsequently ubiquitinates JAK1, activating the NF-κB pathway to promote epithelial-mesenchymal transition in hepatocellular carcinoma cells.","method":"Metabolomics, binding assay, ubiquitination assay, in vitro and in vivo functional experiments","journal":"Hepatology (Baltimore, Md.)","confidence":"Medium","confidence_rationale":"Tier 2–3 / Weak — substrate ubiquitination assay with metabolite-binding component, single study, limited replication","pmids":["40073276"],"is_preprint":false},{"year":2025,"finding":"UBE4B deletion causes KLHL22 accumulation; accumulated KLHL22 stabilizes JAK2 by reducing LNK expression, leading to JAK2 upregulation and PIM1 induction, which mediates resistance to BET inhibitors in hepatocellular carcinoma.","method":"siRNA/CRISPR knockdown, Western blot, epistasis rescue experiments","journal":"Biochemical pharmacology","confidence":"Medium","confidence_rationale":"Tier 2–3 / Weak — genetic epistasis by sequential knockdown, single lab, single study","pmids":["40228637"],"is_preprint":false},{"year":2025,"finding":"UBE4B ubiquitinates and degrades FAT4; loss of UBE4B stabilizes FAT4 and activates autophagy in gastric cancer cells, while UBE4B overexpression inhibits autophagy and promotes proliferation, migration, and invasion.","method":"Co-immunoprecipitation, ubiquitination assay, Western blot, transmission electron microscopy, xenograft model","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2–3 / Weak — Co-IP and ubiquitination assay identifying new substrate, functional in vivo readout, single lab","pmids":["40701960"],"is_preprint":false},{"year":2026,"finding":"UBE4B ubiquitinates NIPSNAP1 under mitochondrial depolarization, enhancing NIPSNAP1 interaction with autophagy adaptors NDP52 and p62/SQSTM1 and promoting lysosome-dependent NIPSNAP1 degradation; this UBE4B-NIPSNAP1 axis mediates Parkin-independent mitophagy in HeLa cells.","method":"Co-immunoprecipitation, in-cell ubiquitination assay (HEK293T and HeLa), lysosome/proteasome inhibitor assays, interaction assay with autophagy adaptors","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — ubiquitination assay in two cell lines, adaptor interaction assay, single lab, no replication yet","pmids":["41596759"],"is_preprint":false},{"year":2026,"finding":"UBE4B ubiquitinates and promotes proteasomal degradation of CCAR2; CCAR2 accumulation upon UBE4B depletion inhibits SIRT1 activity, enhancing p53 acetylation and stability; UBE4B thus suppresses apoptosis via dual pathways: direct p53 ubiquitination and CCAR2 degradation (which indirectly stabilizes p53 via SIRT1).","method":"Orthogonal ubiquitin transfer screening, co-immunoprecipitation, ubiquitination assay, rescue overexpression, transcriptional profiling","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — orthogonal ubiquitin transfer screen for substrate ID plus functional rescue, single lab, single study","pmids":["42074320"],"is_preprint":false},{"year":2011,"finding":"Two alternative splice isoforms of UBE4B (UFD2a-7 and UFD2a-7/7a) are sequentially expressed during myoblast differentiation and are exclusively expressed in mature striated muscle in vertebrates; the muscle-specific isoform UFD2a-7/7a does not interact with VCP/p97 in yeast two-hybrid assays, unlike the canonical isoform.","method":"RT-PCR/Western blot during C2C12 differentiation and cardiotoxin-induced regeneration, yeast two-hybrid for VCP/p97 interaction","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2–3 / Moderate — expression pattern confirmed across species (mouse, zebrafish, human), yeast two-hybrid for interaction, negative interaction result for muscle isoform","pmids":["22174917"],"is_preprint":false}],"current_model":"UBE4B is an E3/E4 ubiquitin ligase that acts as a central regulator of multiple protein degradation pathways: it promotes p53 polyubiquitination and proteasomal degradation in complex with Hdm2 (binding p53 via its SWIB/Hdm2 motif and requiring its U-box for catalysis), is itself regulated by ATR-mediated phosphorylation and Wip1-mediated dephosphorylation after DNA damage, recruits to endosomes via Hrs/ESCRT-0 to ubiquitinate and sort EGFR and APP for lysosomal degradation, polyubiquitylates and degrades KLHL22 to fine-tune mTOR activity in neural development, ubiquitinates NIPSNAP1 to mediate Parkin-independent mitophagy, ubiquitinates HTLV-1 Tax to promote NF-κB activation, and degrades substrates including CCAR2, FAT4, PP2A, and JAK1 in various cancer contexts; additionally a chimeric N-terminal UBE4B fragment fused to NMNAT (the WldS protein) localizes to the nucleus and protects axons from Wallerian degeneration."},"narrative":{"mechanistic_narrative":"UBE4B is a U-box-containing E3/E4 ubiquitin ligase that governs the turnover of substrate proteins across DNA-damage signaling, receptor trafficking, neurogenesis, mitophagy, and oncogenic pathways [PMID:21317885, PMID:36440598]. Its best-characterized role is as a negative regulator of p53: UBE4B physically associates with both p53 and Hdm2 and catalyzes p53 polyubiquitination and proteasomal degradation, thereby suppressing p53-dependent transactivation and apoptosis [PMID:21317885]. Substrate engagement and catalysis are functionally separable, as p53 binding requires the SWIB/Hdm2 motif while the U-box domain is dispensable for binding but essential for degradation [PMID:36865087]. This p53-suppressive activity is controlled by DNA-damage signaling: ATR-mediated phosphorylation of UBE4B lowers its affinity for p53 to permit p53 accumulation, an effect reversed by Wip1-mediated dephosphorylation [PMID:40175346]. UBE4B reinforces p53 control indirectly by ubiquitinating CCAR2, whose loss otherwise represses SIRT1 and stabilizes acetylated p53 [PMID:42074320]. Beyond proteasomal degradation, UBE4B is recruited to endosomes through binding to the ESCRT-0 component Hrs, where it ubiquitinates EGFR and APP to direct their endosomal sorting and lysosomal degradation [PMID:24344129, PMID:32841720]. It also functions in autophagy-lysosome-dependent clearance, ubiquitinating Tau in cooperation with STUB1/CHIP [PMID:34078905] and ubiquitinating NIPSNAP1 to engage the autophagy adaptors NDP52 and p62 during Parkin-independent mitophagy [PMID:41596759]. In neural development, UBE4B polyubiquitylates and degrades KLHL22 to restrain mTOR activity, with its loss causing mTOR hyperactivation, impaired neurogenesis, and seizures rescuable by rapamycin [PMID:36440598]. In disease and cancer contexts, UBE4B ubiquitinates additional substrates including PP2A, FAT4, and JAK1, and modulates HTLV-1 Tax-driven NF-κB activation [PMID:33362245, PMID:35220170, PMID:40073276, PMID:40701960]. Separately, the neuroprotective WldS protein is a chimera of an N-terminal UBE4B fragment fused to NMNAT that localizes to the nucleus and confers dose-dependent protection against Wallerian degeneration [PMID:11770485].","teleology":[{"year":2001,"claim":"Established the first biological link for the UBE4B locus by showing that an N-terminal UBE4B fragment, fused to NMNAT in the WldS protein, confers axonal protection through a nuclear, NMNAT-activity-dependent mechanism.","evidence":"Transgenic mouse expression with subcellular fractionation and enzymatic assay","pmids":["11770485"],"confidence":"High","gaps":["Does not address the function of full-length native UBE4B","Attributes protection to the NMNAT moiety rather than UBE4B catalytic activity"]},{"year":2011,"claim":"Identified UBE4B's core enzymatic role as an E3/E4 ligase that drives p53 polyubiquitination and degradation in concert with Hdm2, defining it as a negative regulator of p53-dependent apoptosis.","evidence":"Reciprocal Co-IP, ubiquitination and transactivation reporter assays, xenograft with silencing","pmids":["21317885"],"confidence":"High","gaps":["Did not map the binding and catalytic determinants within UBE4B","Did not define upstream regulation of the activity"]},{"year":2011,"claim":"Revealed tissue-specific regulation by showing alternative UBE4B isoforms are expressed during myogenesis, with the muscle-specific isoform losing VCP/p97 interaction.","evidence":"RT-PCR/Western blot across differentiation and regeneration, yeast two-hybrid","pmids":["22174917"],"confidence":"Medium","gaps":["Functional consequence of losing VCP/p97 binding not established","No substrate identified for the muscle isoform"]},{"year":2013,"claim":"Extended UBE4B function from proteasomal degradation to endosomal receptor sorting by showing Hrs/ESCRT-0-dependent recruitment and ubiquitination of EGFR for lysosomal degradation.","evidence":"Co-IP, endosomal fractionation, EGFR degradation assay, siRNA knockdown","pmids":["24344129"],"confidence":"High","gaps":["Ubiquitin chain linkage on EGFR not defined","Interplay with USP8 deubiquitination only partially resolved"]},{"year":2015,"claim":"Connected UBE4B to protein quality control by showing its loss promotes clearance of misfolded proteins via proteasomal and autophagic routes, with p53 as a downstream effector.","evidence":"C. elegans epistasis with spr-5/LSD1, mammalian knockdown, inhibitor assays","pmids":["25837623"],"confidence":"High","gaps":["Direct substrates in the quality-control pathway not enumerated","Mechanistic link between UBE4B loss and autophagy not defined"]},{"year":2016,"claim":"Refined the p53 axis by showing UBE4B targets phosphorylated p53 (S15, S392) for degradation after irradiation while its Hdm2 affinity drops, linking degradation to the DNA-damage state.","evidence":"Phospho-specific Co-IP and IR-induced degradation assays","pmids":["26673821"],"confidence":"Medium","gaps":["Single-lab study","Did not identify the kinase or phosphatase controlling the affinity change"]},{"year":2020,"claim":"Demonstrated UBE4B operates in viral oncogenesis by ubiquitinating HTLV-1 Tax with both K48 and K63 chains to enhance NF-κB activation.","evidence":"Yeast two-hybrid, Co-IP, PLA, shRNA/CRISPR knockout, NF-κB reporter","pmids":["33362245"],"confidence":"High","gaps":["Relative contributions of K48 vs K63 chains to NF-κB output not separated","Endogenous host substrates in this context not defined"]},{"year":2020,"claim":"Generalized the endosomal sorting role to neuronal substrates by showing Hrs-dependent UBE4B ubiquitinates APP, controlling its MVB internalization and amyloid-β42 generation.","evidence":"Co-IP, MVB reconstitution in cortical neurons, siRNA, Aβ42 ELISA","pmids":["32841720"],"confidence":"High","gaps":["In vivo relevance to amyloid pathology not tested","Chain type directing APP into ILVs not defined"]},{"year":2021,"claim":"Established UBE4B as a driver of autophagy-lysosome-dependent Tau clearance acting with STUB1/CHIP, implicating it in tauopathy proteostasis.","evidence":"Drosophila miRNA screen, neuroblastoma overexpression, ubiquitination and inhibitor assays, Tau-BiFC mouse","pmids":["34078905"],"confidence":"High","gaps":["Division of labor between UBE4B and STUB1 not resolved","Ubiquitin chain architecture on Tau not defined"]},{"year":2022,"claim":"Defined a developmental function by showing UBE4B degrades KLHL22 to restrain mTOR signaling in neural precursors, with loss causing seizures rescuable by rapamycin.","evidence":"Conditional neural KO mouse, ubiquitination assay, mTOR readout, genetic and rapamycin rescue","pmids":["36440598"],"confidence":"High","gaps":["Whether KLHL22 is the sole relevant neural substrate not established","Upstream signals triggering KLHL22 turnover unknown"]},{"year":2022,"claim":"Expanded the substrate repertoire in cancer by showing UBE4B ubiquitinates PP2A to activate AKT and promote lung adenocarcinoma aggressiveness.","evidence":"Co-IP, ubiquitination assay, overexpression/shRNA in LUAD cells and xenograft","pmids":["35220170"],"confidence":"Medium","gaps":["Single-lab study with limited replication","Direct vs indirect PP2A targeting not fully resolved"]},{"year":2022,"claim":"Placed UBE4B downstream of a splicing regulator by showing SF3B4 sustains UBE4B levels to keep p53 degraded, with SF3B4 loss causing p53/p21-mediated arrest.","evidence":"Co-IP, double siRNA knockdown, Western blot, flow cytometry","pmids":["35996826"],"confidence":"Medium","gaps":["Mechanism by which SF3B4 controls UBE4B levels unclear","Single-study epistasis"]},{"year":2023,"claim":"Dissected the catalytic architecture by showing the SWIB/Hdm2 motif mediates p53 binding while the U-box drives degradation, enabling a peptide that reactivates p53.","evidence":"Domain-mutant Co-IP, transactivation and growth assays, peptide blocking","pmids":["36865087"],"confidence":"Medium","gaps":["No structural model of the SWIB/Hdm2-p53 interface","Single-lab study"]},{"year":2023,"claim":"Showed UBE4B partners with ITCH to form a complex that targets Ku70 and c-FLIPL for branched K48/K63 polyubiquitination, linking it to apoptotic regulation under HDAC inhibition.","evidence":"Co-IP, Western blot, siRNA, caspase-8 activation assay","pmids":["37957138"],"confidence":"Medium","gaps":["Stoichiometry and assembly of the ITCH-UBE4B complex not defined","Single-lab study"]},{"year":2024,"claim":"Uncovered a non-ubiquitin function by showing UBE4B regulates p27 IRES-dependent translation through modulating HuR-p27 5'UTR interaction.","evidence":"Co-IP, RNA pulldown/IRES reporter, knockdown and overexpression","pmids":["38211530"],"confidence":"Medium","gaps":["How a ubiquitin ligase modulates an IRES interaction mechanistically unclear","Single-study finding"]},{"year":2025,"claim":"Defined the kinase/phosphatase circuit controlling p53 regulation by showing ATR phosphorylation reduces UBE4B-p53 binding and Wip1 dephosphorylation restores it.","evidence":"Co-IP, kinase/Wip1 inhibition, phospho-mimetic mutants","pmids":["40175346"],"confidence":"Medium","gaps":["Phosphorylation sites not mapped","Single-lab study"]},{"year":2025,"claim":"Linked UBE4B to metabolite sensing by showing direct DHO binding triggers JAK1 ubiquitination and NF-κB-driven EMT in hepatocellular carcinoma.","evidence":"Metabolomics, binding and ubiquitination assays, in vivo functional experiments","pmids":["40073276"],"confidence":"Medium","gaps":["How DHO binding allosterically alters ligase activity unknown","Single-study finding"]},{"year":2025,"claim":"Connected UBE4B loss to drug resistance by showing KLHL22 accumulation stabilizes JAK2 via reduced LNK, inducing PIM1 and BET-inhibitor resistance.","evidence":"siRNA/CRISPR knockdown and sequential epistasis rescue","pmids":["40228637"],"confidence":"Medium","gaps":["Single-lab epistasis chain","Direct ubiquitination steps not all demonstrated"]},{"year":2025,"claim":"Added FAT4 as a substrate whose UBE4B-mediated degradation restrains autophagy and promotes gastric cancer progression.","evidence":"Co-IP, ubiquitination assay, electron microscopy, xenograft","pmids":["40701960"],"confidence":"Medium","gaps":["Ubiquitin chain type on FAT4 not defined","Single-lab study"]},{"year":2026,"claim":"Established a mitophagy role by showing UBE4B ubiquitinates NIPSNAP1 to recruit NDP52 and p62, driving Parkin-independent mitochondrial clearance.","evidence":"Co-IP, in-cell ubiquitination in HEK293T/HeLa, inhibitor and adaptor-interaction assays","pmids":["41596759"],"confidence":"Medium","gaps":["No replication beyond single lab","Physiological trigger and chain linkage not fully resolved"]},{"year":2026,"claim":"Demonstrated dual p53 control by showing UBE4B degrades CCAR2, whose accumulation otherwise inhibits SIRT1 and stabilizes acetylated p53.","evidence":"Orthogonal ubiquitin transfer screen, Co-IP, ubiquitination and rescue assays, transcriptional profiling","pmids":["42074320"],"confidence":"Medium","gaps":["Relative weighting of direct vs CCAR2-mediated p53 control not quantified","Single-study finding"]},{"year":null,"claim":"How UBE4B selects among its many substrates across distinct compartments and how upstream signals or cofactors switch it between proteasomal, endosomal/lysosomal, and translational functions remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unifying determinant of substrate selectivity defined","Compartment-specific regulation incompletely mapped","Structural basis of catalysis and substrate engagement not solved"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016874","term_label":"ligase activity","supporting_discovery_ids":[1,8,17,18,19]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[1,2,6,7,8,18,19]},{"term_id":"GO:0031386","term_label":"protein tag activity","supporting_discovery_ids":[1,2,8]}],"localization":[{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[2,6]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[1,8,17,18,19]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[7,17,18]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[1,12,19]},{"term_id":"R-HSA-5653656","term_label":"Vesicle-mediated transport","supporting_discovery_ids":[2,6]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[8,15,5]}],"complexes":["ITCH-UBE4B complex"],"partners":["TP53","MDM2","HGS","KLHL22","ITCH","STUB1","ELAVL1","SF3B4"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"O95155","full_name":"Ubiquitin conjugation factor E4 B","aliases":["Homozygously deleted in neuroblastoma 1","RING-type E3 ubiquitin transferase E4 B","Ubiquitin fusion degradation protein 2"],"length_aa":1302,"mass_kda":146.2,"function":"Ubiquitin-protein ligase that probably functions as an E3 ligase in conjunction with specific E1 and E2 ligases (By similarity). May also function as an E4 ligase mediating the assembly of polyubiquitin chains on substrates ubiquitinated by another E3 ubiquitin ligase (By similarity). May regulate myosin assembly in striated muscles together with STUB1 and VCP/p97 by targeting myosin chaperone UNC45B for proteasomal degradation (PubMed:17369820)","subcellular_location":"Cytoplasm; Nucleus","url":"https://www.uniprot.org/uniprotkb/O95155/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/UBE4B","classification":"Not Classified","n_dependent_lines":237,"n_total_lines":1208,"dependency_fraction":0.19619205298013245},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/UBE4B","total_profiled":1310},"omim":[{"mim_id":"613565","title":"UBIQUITINATION FACTOR E4B; UBE4B","url":"https://www.omim.org/entry/613565"},{"mim_id":"604375","title":"HUMAN GROWTH FACTOR-REGULATED TYROSINE KINASE SUBSTRATE; HGS","url":"https://www.omim.org/entry/604375"},{"mim_id":"603158","title":"UBIQUITIN-SPECIFIC PROTEASE 8; USP8","url":"https://www.omim.org/entry/603158"},{"mim_id":"191170","title":"TUMOR PROTEIN p53; TP53","url":"https://www.omim.org/entry/191170"},{"mim_id":"164785","title":"MDM2 PROTOONCOGENE; MDM2","url":"https://www.omim.org/entry/164785"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/UBE4B"},"hgnc":{"alias_symbol":["UBOX3","E4","UFD2","KIAA0684"],"prev_symbol":[]},"alphafold":{"accession":"O95155","domains":[{"cath_id":"-","chopping":"155-229_418-481","consensus_level":"medium","plddt":87.0833,"start":155,"end":481},{"cath_id":"-","chopping":"1021-1222","consensus_level":"medium","plddt":90.0074,"start":1021,"end":1222},{"cath_id":"3.30.40.10","chopping":"1231-1302","consensus_level":"high","plddt":89.2303,"start":1231,"end":1302}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O95155","model_url":"https://alphafold.ebi.ac.uk/files/AF-O95155-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O95155-F1-predicted_aligned_error_v6.png","plddt_mean":75.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=UBE4B","jax_strain_url":"https://www.jax.org/strain/search?query=UBE4B"},"sequence":{"accession":"O95155","fasta_url":"https://rest.uniprot.org/uniprotkb/O95155.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O95155/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O95155"}},"corpus_meta":[{"pmid":"11770485","id":"PMC_11770485","title":"Wallerian degeneration of injured axons and synapses is delayed by a Ube4b/Nmnat chimeric gene.","date":"2001","source":"Nature neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/11770485","citation_count":515,"is_preprint":false},{"pmid":"21317885","id":"PMC_21317885","title":"UBE4B promotes Hdm2-mediated degradation of the tumor suppressor p53.","date":"2011","source":"Nature medicine","url":"https://pubmed.ncbi.nlm.nih.gov/21317885","citation_count":105,"is_preprint":false},{"pmid":"12231635","id":"PMC_12231635","title":"Age-dependent synapse withdrawal at axotomised neuromuscular junctions in Wld(s) mutant and Ube4b/Nmnat transgenic mice.","date":"2002","source":"The Journal of physiology","url":"https://pubmed.ncbi.nlm.nih.gov/12231635","citation_count":84,"is_preprint":false},{"pmid":"34078905","id":"PMC_34078905","title":"UBE4B, a microRNA-9 target gene, promotes autophagy-mediated Tau degradation.","date":"2021","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/34078905","citation_count":58,"is_preprint":false},{"pmid":"12700669","id":"PMC_12700669","title":"Screening for gene mutations in a 500 kb neuroblastoma tumor suppressor candidate region in chromosome 1p; mutation and stage-specific expression in UBE4B/UFD2.","date":"2003","source":"Oncogene","url":"https://pubmed.ncbi.nlm.nih.gov/12700669","citation_count":45,"is_preprint":false},{"pmid":"24344129","id":"PMC_24344129","title":"UBE4B protein couples ubiquitination and sorting machineries to enable epidermal growth factor receptor (EGFR) degradation.","date":"2013","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/24344129","citation_count":43,"is_preprint":false},{"pmid":"25837623","id":"PMC_25837623","title":"Regulation of protein quality control by UBE4B and LSD1 through p53-mediated transcription.","date":"2015","source":"PLoS biology","url":"https://pubmed.ncbi.nlm.nih.gov/25837623","citation_count":37,"is_preprint":false},{"pmid":"22990745","id":"PMC_22990745","title":"UBE4B levels are correlated with clinical outcomes in neuroblastoma patients and with altered neuroblastoma cell proliferation and sensitivity to epidermal growth factor receptor inhibitors.","date":"2012","source":"Cancer","url":"https://pubmed.ncbi.nlm.nih.gov/22990745","citation_count":35,"is_preprint":false},{"pmid":"28483517","id":"PMC_28483517","title":"MicroRNA-1301 suppresses tumor cell migration and invasion by targeting the p53/UBE4B pathway in multiple human cancer cells.","date":"2017","source":"Cancer letters","url":"https://pubmed.ncbi.nlm.nih.gov/28483517","citation_count":35,"is_preprint":false},{"pmid":"31040698","id":"PMC_31040698","title":"Silencing UBE4B induces nasopharyngeal carcinoma apoptosis through the activation of caspase3 and p53.","date":"2019","source":"OncoTargets and therapy","url":"https://pubmed.ncbi.nlm.nih.gov/31040698","citation_count":30,"is_preprint":false},{"pmid":"24587254","id":"PMC_24587254","title":"Regulation of p53 level by UBE4B in breast cancer.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24587254","citation_count":29,"is_preprint":false},{"pmid":"26673821","id":"PMC_26673821","title":"UBE4B targets phosphorylated p53 at serines 15 and 392 for degradation.","date":"2016","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/26673821","citation_count":28,"is_preprint":false},{"pmid":"31878315","id":"PMC_31878315","title":"The Role of E3, E4 Ubiquitin Ligase (UBE4B) in Human Pathologies.","date":"2019","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/31878315","citation_count":26,"is_preprint":false},{"pmid":"16386891","id":"PMC_16386891","title":"The two human homologues of yeast UFD2 ubiquitination factor, UBE4A and UBE4B, are located in common neuroblastoma deletion regions and are subject to mutations in tumours.","date":"2006","source":"European journal of cancer (Oxford, England : 1990)","url":"https://pubmed.ncbi.nlm.nih.gov/16386891","citation_count":23,"is_preprint":false},{"pmid":"33362245","id":"PMC_33362245","title":"The E3/E4 ubiquitin conjugation factor UBE4B interacts with and ubiquitinates the HTLV-1 Tax oncoprotein to promote NF-κB activation.","date":"2020","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/33362245","citation_count":22,"is_preprint":false},{"pmid":"32841720","id":"PMC_32841720","title":"The ubiquitin ligase UBE4B regulates amyloid precursor protein ubiquitination, endosomal trafficking, and amyloid β42 generation and secretion.","date":"2020","source":"Molecular and cellular neurosciences","url":"https://pubmed.ncbi.nlm.nih.gov/32841720","citation_count":21,"is_preprint":false},{"pmid":"31475882","id":"PMC_31475882","title":"Low UBE4B expression increases sensitivity of chemoresistant neuroblastoma cells to EGFR and STAT5 inhibition.","date":"2019","source":"Cancer biology & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/31475882","citation_count":13,"is_preprint":false},{"pmid":"35996826","id":"PMC_35996826","title":"SF3B4 Depletion Retards the Growth of A549 Non-Small Cell Lung Cancer Cells via UBE4B-Mediated Regulation of p53/p21 and p27 Expression.","date":"2022","source":"Molecules and cells","url":"https://pubmed.ncbi.nlm.nih.gov/35996826","citation_count":13,"is_preprint":false},{"pmid":"22174917","id":"PMC_22174917","title":"A novel conserved isoform of the ubiquitin ligase UFD2a/UBE4B is expressed exclusively in mature striated muscle cells.","date":"2011","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/22174917","citation_count":11,"is_preprint":false},{"pmid":"40073276","id":"PMC_40073276","title":"CAD manipulates tumor intrinsic DHO/UBE4B/NF-κB pathway and fuels macrophage cross-talk, promoting HCC metastasis.","date":"2025","source":"Hepatology (Baltimore, Md.)","url":"https://pubmed.ncbi.nlm.nih.gov/40073276","citation_count":8,"is_preprint":false},{"pmid":"36865087","id":"PMC_36865087","title":"The SWIB/MDM2 motif of UBE4B activates the p53 pathway.","date":"2023","source":"Molecular therapy. Nucleic acids","url":"https://pubmed.ncbi.nlm.nih.gov/36865087","citation_count":8,"is_preprint":false},{"pmid":"36440598","id":"PMC_36440598","title":"Fine-tuning of mTOR signaling by the UBE4B-KLHL22 E3 ubiquitin ligase cascade in brain development.","date":"2022","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/36440598","citation_count":7,"is_preprint":false},{"pmid":"35220170","id":"PMC_35220170","title":"UBE4B promotes the development of lung adenocarcinoma by enhancing proliferation, migration and glycolysis via PP2A/AKT signaling.","date":"2022","source":"Pathology, research and practice","url":"https://pubmed.ncbi.nlm.nih.gov/35220170","citation_count":7,"is_preprint":false},{"pmid":"40701960","id":"PMC_40701960","title":"UBE4B promotes gastric cancer proliferation and metastasis by mediating FAT4 ubiquitination and degradation.","date":"2025","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/40701960","citation_count":6,"is_preprint":false},{"pmid":"37957138","id":"PMC_37957138","title":"UBE4B interacts with the ITCH E3 ubiquitin ligase to induce Ku70 and c-FLIPL polyubiquitination and enhanced neuroblastoma apoptosis.","date":"2023","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/37957138","citation_count":6,"is_preprint":false},{"pmid":"38211530","id":"PMC_38211530","title":"UBE4B regulates p27 expression in A549 NSCLC cells through regulating the interaction of HuR and the p27 5' UTR.","date":"2024","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/38211530","citation_count":3,"is_preprint":false},{"pmid":"40175346","id":"PMC_40175346","title":"Deciphering UBE4B phosphorylation dynamics: a key mechanism in p53 accumulation and cancer cell response to DNA damage.","date":"2025","source":"Cell death discovery","url":"https://pubmed.ncbi.nlm.nih.gov/40175346","citation_count":3,"is_preprint":false},{"pmid":"40228637","id":"PMC_40228637","title":"UBE4B modulates BET inhibitor sensitivity via KLHL22-JAK2-PIM1 axis in hepatocellular carcinoma.","date":"2025","source":"Biochemical pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/40228637","citation_count":1,"is_preprint":false},{"pmid":"41596759","id":"PMC_41596759","title":"UBE4B Mediates Mitophagy via NIPSNAP1 Ubiquitination and NDP52 Recruitment.","date":"2026","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/41596759","citation_count":0,"is_preprint":false},{"pmid":"42074320","id":"PMC_42074320","title":"Dual Pathways of UBE4B Inhibit Apoptosis in p53-Positive Tumor Cells via CCAR2 Degradation.","date":"2026","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/42074320","citation_count":0,"is_preprint":false},{"pmid":"40886930","id":"PMC_40886930","title":"UBE4B-driven suppression of megakaryocyte maturation by HBV: A novel mechanism linking viral infection to thrombocytopenia via p53-ERK1/2 crosstalk.","date":"2025","source":"Cellular signalling","url":"https://pubmed.ncbi.nlm.nih.gov/40886930","citation_count":0,"is_preprint":false},{"pmid":"41936850","id":"PMC_41936850","title":"Nuclear IL-33-driven UBE4B expression tilts human macrophages toward the M2 phenotype via p53 ubiquitination.","date":"2026","source":"Biochimica et biophysica acta. Molecular cell research","url":"https://pubmed.ncbi.nlm.nih.gov/41936850","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":17451,"output_tokens":5131,"usd":0.064659,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":13356,"output_tokens":5942,"usd":0.107665,"stage2_stop_reason":"end_turn"},"total_usd":0.172324,"stage1_batch_id":"msgbatch_017qqVz33Ga63SCDwzb35XPb","stage2_batch_id":"msgbatch_01Scr2Ei9x4HJMiRGxwrmvLK","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2001,\n      \"finding\": \"The WldS protective gene encodes an N-terminal fragment of UBE4B fused to NMNAT; the chimeric Wld protein localizes predominantly to the nucleus and confers dose-dependent protection against Wallerian degeneration, with NMNAT enzyme activity (not NAD+ content) increased fourfold, indicating an indirect nuclear mechanism of axon protection.\",\n      \"method\": \"Transgenic mouse expression, subcellular fractionation/localization, enzymatic activity assay\",\n      \"journal\": \"Nature neuroscience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct identification of protective gene, localization experiment, enzymatic assay, replicated across multiple transgenic lines\",\n      \"pmids\": [\"11770485\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"UBE4B physically interacts with both p53 and Hdm2, promotes p53 polyubiquitination and proteasomal degradation, inhibits p53-dependent transactivation and apoptosis, functioning as an E3/E4 ubiquitin ligase in the p53 regulatory axis.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, transactivation reporter assay, xenograft tumor model with UBE4B silencing\",\n      \"journal\": \"Nature medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — reciprocal Co-IP, in vitro ubiquitination assay, functional rescue experiments, replicated in subsequent studies\",\n      \"pmids\": [\"21317885\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"UBE4B is recruited to endosomes upon EGFR activation by binding to Hrs (ESCRT-0 component); UBE4B ubiquitinates EGFR and regulates its endosomal sorting and lysosomal degradation, coordinating with the deubiquitinase USP8.\",\n      \"method\": \"Co-immunoprecipitation, endosomal fractionation, EGFR degradation assay, siRNA knockdown with functional readout\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, substrate identification, endosomal localization with functional consequence, multiple orthogonal methods in single lab\",\n      \"pmids\": [\"24344129\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Loss of UBE4B (orthologue ufd-2 in C. elegans) synergizes with loss of LSD1 (spr-5) to suppress proteotoxic neurodegeneration; in mammalian cells, loss of UBE4B promotes clearance of misfolded proteins via both proteasomal and autophagic pathways, with p53 identified as a downstream transcriptional effector of this quality control pathway.\",\n      \"method\": \"C. elegans genetic epistasis (double mutant), mammalian cell knockdown, proteasome/autophagy inhibitor assays\",\n      \"journal\": \"PLoS biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis in vivo, mechanistic follow-up in mammalian cells, multiple orthogonal methods\",\n      \"pmids\": [\"25837623\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"UBE4B co-immunoprecipitates with phosphorylated p53 at serines 15 and 392; UBE4B promotes degradation of endogenous phospho-p53(S15) and phospho-p53(S392) in response to ionizing radiation, and its affinity for Hdm2 is decreased after DNA damage.\",\n      \"method\": \"Co-immunoprecipitation with phospho-specific antibodies, IR-induced p53 degradation assay, transactivation reporter assay\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — Co-IP and functional assays in single lab, single study\",\n      \"pmids\": [\"26673821\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"UBE4B interacts with and ubiquitinates the HTLV-1 Tax oncoprotein; UBE4B overexpression enhances Tax-induced NF-κB activation, and UBE4B knockdown/knockout attenuates both K48- and K63-linked polyubiquitination of Tax and impairs NF-κB target gene induction.\",\n      \"method\": \"Yeast two-hybrid screen, co-immunoprecipitation, proximity ligation assay, confocal microscopy, shRNA/CRISPR knockout, NF-κB reporter assay\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — yeast two-hybrid confirmed by reciprocal Co-IP and PLA, functional validation by KD and KO with orthogonal methods\",\n      \"pmids\": [\"33362245\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"UBE4B binds to Hrs (ESCRT-0) on endosomes and ubiquitinates APP; depletion of UBE4B in neurons inhibits APP ubiquitination and internalization into multivesicular body intraluminal vesicles, resulting in increased endosomal Aβ42 generation and secretion.\",\n      \"method\": \"Co-immunoprecipitation, MVB reconstitution in cortical neurons, siRNA knockdown, ELISA for Aβ42\",\n      \"journal\": \"Molecular and cellular neurosciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — substrate identification, endosomal reconstitution, functional knockdown readout, multiple methods in single study\",\n      \"pmids\": [\"32841720\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"UBE4B (orthologue CG11070 in Drosophila) promotes ubiquitination and autophagy-lysosome-dependent degradation of Tau; in mammalian neuroblastoma cells UBE4B together with STUB1 (CHIP) increases ubiquitination and degradation of both total and phosphorylated Tau; autophagy inhibitors block this degradation.\",\n      \"method\": \"Drosophila miRNA screen, overexpression in neuroblastoma cells, ubiquitination assay, autophagy/proteasome inhibitor assays, Tau-BiFC mouse model\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic screen validated in multiple model systems (fly, mammalian cells, mouse), orthogonal inhibitor assays\",\n      \"pmids\": [\"34078905\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"UBE4B polyubiquitylates and degrades KLHL22 (an E3 ligase that degrades GATOR1 component DEPDC5); loss of UBE4B causes KLHL22 accumulation and mTOR hyperactivation in neural precursor cells, leading to impaired neurogenesis and seizures; rapamycin rescues neurogenesis defects in Ube4b conditional knockout mice.\",\n      \"method\": \"Conditional neural knockout mouse, ubiquitination assay, mTOR activity measurement, genetic rescue (KLHL22 suppression), pharmacological rescue (rapamycin)\",\n      \"journal\": \"Development (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo conditional KO with defined phenotype, substrate identification with ubiquitination assay, genetic and pharmacological rescue\",\n      \"pmids\": [\"36440598\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"UBE4B ubiquitinates PP2A, leading to PP2A degradation and consequent AKT activation; this mechanism promotes lung adenocarcinoma cell proliferation, migration, and glycolysis, effects reversed by PP2A overexpression.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, overexpression/shRNA in LUAD cells and xenograft\",\n      \"journal\": \"Pathology, research and practice\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — Co-IP and ubiquitination assay, single lab, limited replication\",\n      \"pmids\": [\"35220170\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"SF3B4 interacts with UBE4B (Co-IP); SF3B4 depletion reduces UBE4B levels, which in turn reduces polyubiquitinated p53 levels and causes p53/p21 accumulation and cell cycle arrest in A549 lung cancer cells.\",\n      \"method\": \"Co-immunoprecipitation, siRNA double knockdown, Western blot, flow cytometry\",\n      \"journal\": \"Molecules and cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Weak — Co-IP and knockdown epistasis, single lab, single study\",\n      \"pmids\": [\"35996826\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The SWIB/Hdm2 motif of UBE4B is required for p53 binding; the UBE4B U-box domain does not bind p53 but is essential for p53 degradation and acts in a dominant-negative manner to stabilize p53 when expressed alone; a UBE4B peptide spanning the SWIB/Hdm2 motif blocks p53-UBE4B interaction and activates p53-dependent transactivation and growth inhibition.\",\n      \"method\": \"Co-immunoprecipitation with domain mutants, transactivation reporter assay, growth inhibition assay, peptide blocking experiment\",\n      \"journal\": \"Molecular therapy. Nucleic acids\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — domain mutagenesis with functional readout, single lab, single study\",\n      \"pmids\": [\"36865087\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"UBE4B interacts with ITCH E3 ligase via ITCH WW domains; ITCH activation leads to ITCH-UBE4B complex formation and recruitment of Ku70 and c-FLIPL, promoting their Lys48/Lys63-branched polyubiquitination and proteasomal degradation; HDAC inhibition induces Ku70 acetylation, releasing c-FLIPL and Bax and enhancing ITCH-UBE4B-mediated polyubiquitination and apoptosis.\",\n      \"method\": \"Co-immunoprecipitation, Western blot, siRNA knockdown, caspase 8 activation assay\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Weak — Co-IP, substrate ubiquitination assay, functional KD readout, single lab\",\n      \"pmids\": [\"37957138\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"UBE4B interacts with the RNA-binding protein HuR; UBE4B regulates p27 translation via the cap-independent IRES pathway by modulating the interaction between HuR and the p27 5' UTR IRES, thereby suppressing p27 protein levels independently of ubiquitin-mediated degradation.\",\n      \"method\": \"Co-immunoprecipitation, RNA pulldown/IRES reporter assay, siRNA knockdown and overexpression, Western blot\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Weak — Co-IP plus functional IRES assay, novel non-ubiquitin mechanism, single lab, single study\",\n      \"pmids\": [\"38211530\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ATR-mediated phosphorylation of UBE4B reduces its binding affinity to p53, causing p53 accumulation after DNA damage; the phosphatase Wip1 dephosphorylates UBE4B to restore its p53-binding and degradation activity; inhibition of Wip1 increases UBE4B phosphorylation and further accumulates p53.\",\n      \"method\": \"Co-immunoprecipitation, kinase inhibitor assays, Wip1 inhibition, phosphorylation-mimetic mutants, Western blot\",\n      \"journal\": \"Cell death discovery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — Co-IP with PTM analysis, pharmacological and genetic modulation, single lab study\",\n      \"pmids\": [\"40175346\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"UBE4B directly binds DHO (dihydroorotic acid) and subsequently ubiquitinates JAK1, activating the NF-κB pathway to promote epithelial-mesenchymal transition in hepatocellular carcinoma cells.\",\n      \"method\": \"Metabolomics, binding assay, ubiquitination assay, in vitro and in vivo functional experiments\",\n      \"journal\": \"Hepatology (Baltimore, Md.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Weak — substrate ubiquitination assay with metabolite-binding component, single study, limited replication\",\n      \"pmids\": [\"40073276\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"UBE4B deletion causes KLHL22 accumulation; accumulated KLHL22 stabilizes JAK2 by reducing LNK expression, leading to JAK2 upregulation and PIM1 induction, which mediates resistance to BET inhibitors in hepatocellular carcinoma.\",\n      \"method\": \"siRNA/CRISPR knockdown, Western blot, epistasis rescue experiments\",\n      \"journal\": \"Biochemical pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Weak — genetic epistasis by sequential knockdown, single lab, single study\",\n      \"pmids\": [\"40228637\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"UBE4B ubiquitinates and degrades FAT4; loss of UBE4B stabilizes FAT4 and activates autophagy in gastric cancer cells, while UBE4B overexpression inhibits autophagy and promotes proliferation, migration, and invasion.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, Western blot, transmission electron microscopy, xenograft model\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Weak — Co-IP and ubiquitination assay identifying new substrate, functional in vivo readout, single lab\",\n      \"pmids\": [\"40701960\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"UBE4B ubiquitinates NIPSNAP1 under mitochondrial depolarization, enhancing NIPSNAP1 interaction with autophagy adaptors NDP52 and p62/SQSTM1 and promoting lysosome-dependent NIPSNAP1 degradation; this UBE4B-NIPSNAP1 axis mediates Parkin-independent mitophagy in HeLa cells.\",\n      \"method\": \"Co-immunoprecipitation, in-cell ubiquitination assay (HEK293T and HeLa), lysosome/proteasome inhibitor assays, interaction assay with autophagy adaptors\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — ubiquitination assay in two cell lines, adaptor interaction assay, single lab, no replication yet\",\n      \"pmids\": [\"41596759\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"UBE4B ubiquitinates and promotes proteasomal degradation of CCAR2; CCAR2 accumulation upon UBE4B depletion inhibits SIRT1 activity, enhancing p53 acetylation and stability; UBE4B thus suppresses apoptosis via dual pathways: direct p53 ubiquitination and CCAR2 degradation (which indirectly stabilizes p53 via SIRT1).\",\n      \"method\": \"Orthogonal ubiquitin transfer screening, co-immunoprecipitation, ubiquitination assay, rescue overexpression, transcriptional profiling\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — orthogonal ubiquitin transfer screen for substrate ID plus functional rescue, single lab, single study\",\n      \"pmids\": [\"42074320\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Two alternative splice isoforms of UBE4B (UFD2a-7 and UFD2a-7/7a) are sequentially expressed during myoblast differentiation and are exclusively expressed in mature striated muscle in vertebrates; the muscle-specific isoform UFD2a-7/7a does not interact with VCP/p97 in yeast two-hybrid assays, unlike the canonical isoform.\",\n      \"method\": \"RT-PCR/Western blot during C2C12 differentiation and cardiotoxin-induced regeneration, yeast two-hybrid for VCP/p97 interaction\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2–3 / Moderate — expression pattern confirmed across species (mouse, zebrafish, human), yeast two-hybrid for interaction, negative interaction result for muscle isoform\",\n      \"pmids\": [\"22174917\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"UBE4B is an E3/E4 ubiquitin ligase that acts as a central regulator of multiple protein degradation pathways: it promotes p53 polyubiquitination and proteasomal degradation in complex with Hdm2 (binding p53 via its SWIB/Hdm2 motif and requiring its U-box for catalysis), is itself regulated by ATR-mediated phosphorylation and Wip1-mediated dephosphorylation after DNA damage, recruits to endosomes via Hrs/ESCRT-0 to ubiquitinate and sort EGFR and APP for lysosomal degradation, polyubiquitylates and degrades KLHL22 to fine-tune mTOR activity in neural development, ubiquitinates NIPSNAP1 to mediate Parkin-independent mitophagy, ubiquitinates HTLV-1 Tax to promote NF-κB activation, and degrades substrates including CCAR2, FAT4, PP2A, and JAK1 in various cancer contexts; additionally a chimeric N-terminal UBE4B fragment fused to NMNAT (the WldS protein) localizes to the nucleus and protects axons from Wallerian degeneration.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"UBE4B is a U-box-containing E3/E4 ubiquitin ligase that governs the turnover of substrate proteins across DNA-damage signaling, receptor trafficking, neurogenesis, mitophagy, and oncogenic pathways [#1, #8]. Its best-characterized role is as a negative regulator of p53: UBE4B physically associates with both p53 and Hdm2 and catalyzes p53 polyubiquitination and proteasomal degradation, thereby suppressing p53-dependent transactivation and apoptosis [#1]. Substrate engagement and catalysis are functionally separable, as p53 binding requires the SWIB/Hdm2 motif while the U-box domain is dispensable for binding but essential for degradation [#11]. This p53-suppressive activity is controlled by DNA-damage signaling: ATR-mediated phosphorylation of UBE4B lowers its affinity for p53 to permit p53 accumulation, an effect reversed by Wip1-mediated dephosphorylation [#14]. UBE4B reinforces p53 control indirectly by ubiquitinating CCAR2, whose loss otherwise represses SIRT1 and stabilizes acetylated p53 [#19]. Beyond proteasomal degradation, UBE4B is recruited to endosomes through binding to the ESCRT-0 component Hrs, where it ubiquitinates EGFR and APP to direct their endosomal sorting and lysosomal degradation [#2, #6]. It also functions in autophagy-lysosome-dependent clearance, ubiquitinating Tau in cooperation with STUB1/CHIP [#7] and ubiquitinating NIPSNAP1 to engage the autophagy adaptors NDP52 and p62 during Parkin-independent mitophagy [#18]. In neural development, UBE4B polyubiquitylates and degrades KLHL22 to restrain mTOR activity, with its loss causing mTOR hyperactivation, impaired neurogenesis, and seizures rescuable by rapamycin [#8]. In disease and cancer contexts, UBE4B ubiquitinates additional substrates including PP2A, FAT4, and JAK1, and modulates HTLV-1 Tax-driven NF-\\u03baB activation [#5, #9, #15, #17]. Separately, the neuroprotective WldS protein is a chimera of an N-terminal UBE4B fragment fused to NMNAT that localizes to the nucleus and confers dose-dependent protection against Wallerian degeneration [#0].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Established the first biological link for the UBE4B locus by showing that an N-terminal UBE4B fragment, fused to NMNAT in the WldS protein, confers axonal protection through a nuclear, NMNAT-activity-dependent mechanism.\",\n      \"evidence\": \"Transgenic mouse expression with subcellular fractionation and enzymatic assay\",\n      \"pmids\": [\"11770485\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Does not address the function of full-length native UBE4B\", \"Attributes protection to the NMNAT moiety rather than UBE4B catalytic activity\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Identified UBE4B's core enzymatic role as an E3/E4 ligase that drives p53 polyubiquitination and degradation in concert with Hdm2, defining it as a negative regulator of p53-dependent apoptosis.\",\n      \"evidence\": \"Reciprocal Co-IP, ubiquitination and transactivation reporter assays, xenograft with silencing\",\n      \"pmids\": [\"21317885\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not map the binding and catalytic determinants within UBE4B\", \"Did not define upstream regulation of the activity\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Revealed tissue-specific regulation by showing alternative UBE4B isoforms are expressed during myogenesis, with the muscle-specific isoform losing VCP/p97 interaction.\",\n      \"evidence\": \"RT-PCR/Western blot across differentiation and regeneration, yeast two-hybrid\",\n      \"pmids\": [\"22174917\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of losing VCP/p97 binding not established\", \"No substrate identified for the muscle isoform\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Extended UBE4B function from proteasomal degradation to endosomal receptor sorting by showing Hrs/ESCRT-0-dependent recruitment and ubiquitination of EGFR for lysosomal degradation.\",\n      \"evidence\": \"Co-IP, endosomal fractionation, EGFR degradation assay, siRNA knockdown\",\n      \"pmids\": [\"24344129\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Ubiquitin chain linkage on EGFR not defined\", \"Interplay with USP8 deubiquitination only partially resolved\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Connected UBE4B to protein quality control by showing its loss promotes clearance of misfolded proteins via proteasomal and autophagic routes, with p53 as a downstream effector.\",\n      \"evidence\": \"C. elegans epistasis with spr-5/LSD1, mammalian knockdown, inhibitor assays\",\n      \"pmids\": [\"25837623\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct substrates in the quality-control pathway not enumerated\", \"Mechanistic link between UBE4B loss and autophagy not defined\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Refined the p53 axis by showing UBE4B targets phosphorylated p53 (S15, S392) for degradation after irradiation while its Hdm2 affinity drops, linking degradation to the DNA-damage state.\",\n      \"evidence\": \"Phospho-specific Co-IP and IR-induced degradation assays\",\n      \"pmids\": [\"26673821\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab study\", \"Did not identify the kinase or phosphatase controlling the affinity change\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Demonstrated UBE4B operates in viral oncogenesis by ubiquitinating HTLV-1 Tax with both K48 and K63 chains to enhance NF-\\u03baB activation.\",\n      \"evidence\": \"Yeast two-hybrid, Co-IP, PLA, shRNA/CRISPR knockout, NF-\\u03baB reporter\",\n      \"pmids\": [\"33362245\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contributions of K48 vs K63 chains to NF-\\u03baB output not separated\", \"Endogenous host substrates in this context not defined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Generalized the endosomal sorting role to neuronal substrates by showing Hrs-dependent UBE4B ubiquitinates APP, controlling its MVB internalization and amyloid-\\u03b242 generation.\",\n      \"evidence\": \"Co-IP, MVB reconstitution in cortical neurons, siRNA, A\\u03b242 ELISA\",\n      \"pmids\": [\"32841720\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo relevance to amyloid pathology not tested\", \"Chain type directing APP into ILVs not defined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Established UBE4B as a driver of autophagy-lysosome-dependent Tau clearance acting with STUB1/CHIP, implicating it in tauopathy proteostasis.\",\n      \"evidence\": \"Drosophila miRNA screen, neuroblastoma overexpression, ubiquitination and inhibitor assays, Tau-BiFC mouse\",\n      \"pmids\": [\"34078905\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Division of labor between UBE4B and STUB1 not resolved\", \"Ubiquitin chain architecture on Tau not defined\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined a developmental function by showing UBE4B degrades KLHL22 to restrain mTOR signaling in neural precursors, with loss causing seizures rescuable by rapamycin.\",\n      \"evidence\": \"Conditional neural KO mouse, ubiquitination assay, mTOR readout, genetic and rapamycin rescue\",\n      \"pmids\": [\"36440598\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether KLHL22 is the sole relevant neural substrate not established\", \"Upstream signals triggering KLHL22 turnover unknown\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Expanded the substrate repertoire in cancer by showing UBE4B ubiquitinates PP2A to activate AKT and promote lung adenocarcinoma aggressiveness.\",\n      \"evidence\": \"Co-IP, ubiquitination assay, overexpression/shRNA in LUAD cells and xenograft\",\n      \"pmids\": [\"35220170\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab study with limited replication\", \"Direct vs indirect PP2A targeting not fully resolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Placed UBE4B downstream of a splicing regulator by showing SF3B4 sustains UBE4B levels to keep p53 degraded, with SF3B4 loss causing p53/p21-mediated arrest.\",\n      \"evidence\": \"Co-IP, double siRNA knockdown, Western blot, flow cytometry\",\n      \"pmids\": [\"35996826\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which SF3B4 controls UBE4B levels unclear\", \"Single-study epistasis\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Dissected the catalytic architecture by showing the SWIB/Hdm2 motif mediates p53 binding while the U-box drives degradation, enabling a peptide that reactivates p53.\",\n      \"evidence\": \"Domain-mutant Co-IP, transactivation and growth assays, peptide blocking\",\n      \"pmids\": [\"36865087\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of the SWIB/Hdm2-p53 interface\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Showed UBE4B partners with ITCH to form a complex that targets Ku70 and c-FLIPL for branched K48/K63 polyubiquitination, linking it to apoptotic regulation under HDAC inhibition.\",\n      \"evidence\": \"Co-IP, Western blot, siRNA, caspase-8 activation assay\",\n      \"pmids\": [\"37957138\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Stoichiometry and assembly of the ITCH-UBE4B complex not defined\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Uncovered a non-ubiquitin function by showing UBE4B regulates p27 IRES-dependent translation through modulating HuR-p27 5'UTR interaction.\",\n      \"evidence\": \"Co-IP, RNA pulldown/IRES reporter, knockdown and overexpression\",\n      \"pmids\": [\"38211530\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How a ubiquitin ligase modulates an IRES interaction mechanistically unclear\", \"Single-study finding\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Defined the kinase/phosphatase circuit controlling p53 regulation by showing ATR phosphorylation reduces UBE4B-p53 binding and Wip1 dephosphorylation restores it.\",\n      \"evidence\": \"Co-IP, kinase/Wip1 inhibition, phospho-mimetic mutants\",\n      \"pmids\": [\"40175346\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Phosphorylation sites not mapped\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Linked UBE4B to metabolite sensing by showing direct DHO binding triggers JAK1 ubiquitination and NF-\\u03baB-driven EMT in hepatocellular carcinoma.\",\n      \"evidence\": \"Metabolomics, binding and ubiquitination assays, in vivo functional experiments\",\n      \"pmids\": [\"40073276\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"How DHO binding allosterically alters ligase activity unknown\", \"Single-study finding\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Connected UBE4B loss to drug resistance by showing KLHL22 accumulation stabilizes JAK2 via reduced LNK, inducing PIM1 and BET-inhibitor resistance.\",\n      \"evidence\": \"siRNA/CRISPR knockdown and sequential epistasis rescue\",\n      \"pmids\": [\"40228637\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab epistasis chain\", \"Direct ubiquitination steps not all demonstrated\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Added FAT4 as a substrate whose UBE4B-mediated degradation restrains autophagy and promotes gastric cancer progression.\",\n      \"evidence\": \"Co-IP, ubiquitination assay, electron microscopy, xenograft\",\n      \"pmids\": [\"40701960\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ubiquitin chain type on FAT4 not defined\", \"Single-lab study\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Established a mitophagy role by showing UBE4B ubiquitinates NIPSNAP1 to recruit NDP52 and p62, driving Parkin-independent mitochondrial clearance.\",\n      \"evidence\": \"Co-IP, in-cell ubiquitination in HEK293T/HeLa, inhibitor and adaptor-interaction assays\",\n      \"pmids\": [\"41596759\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No replication beyond single lab\", \"Physiological trigger and chain linkage not fully resolved\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Demonstrated dual p53 control by showing UBE4B degrades CCAR2, whose accumulation otherwise inhibits SIRT1 and stabilizes acetylated p53.\",\n      \"evidence\": \"Orthogonal ubiquitin transfer screen, Co-IP, ubiquitination and rescue assays, transcriptional profiling\",\n      \"pmids\": [\"42074320\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Relative weighting of direct vs CCAR2-mediated p53 control not quantified\", \"Single-study finding\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How UBE4B selects among its many substrates across distinct compartments and how upstream signals or cofactors switch it between proteasomal, endosomal/lysosomal, and translational functions remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unifying determinant of substrate selectivity defined\", \"Compartment-specific regulation incompletely mapped\", \"Structural basis of catalysis and substrate engagement not solved\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016874\", \"supporting_discovery_ids\": [1, 8, 17, 18, 19]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [1, 2, 6, 7, 8, 18, 19]},\n      {\"term_id\": \"GO:0031386\", \"supporting_discovery_ids\": [1, 2, 8]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [2, 6]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [1, 8, 17, 18, 19]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [7, 17, 18]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [1, 12, 19]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [2, 6]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [8, 15, 5]}\n    ],\n    \"complexes\": [\n      \"ITCH-UBE4B complex\"\n    ],\n    \"partners\": [\n      \"TP53\",\n      \"MDM2\",\n      \"HGS\",\n      \"KLHL22\",\n      \"ITCH\",\n      \"STUB1\",\n      \"ELAVL1\",\n      \"SF3B4\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":10,"faith_total":10,"faith_pct":100.0}}