{"gene":"UBA52","run_date":"2026-06-10T10:51:56","timeline":{"discoveries":[{"year":2016,"finding":"UBA52 encodes a fusion protein of ubiquitin and ribosomal protein L40 (RPL40); proteolytic cleavage of RPL40 from UBA52 is required for maintaining protein synthesis, and RPL40 forms a ribosomal complex with ubiquitin co-supplied by UBA52. Expression of RPL40 alone (without the ubiquitin moiety) is insufficient to regulate cyclin D expression or rescue cell-cycle arrest caused by UBA52 deficiency.","method":"Knockout mouse model (Uba52-deficient embryonic lethality), cell-based overexpression/rescue assays, ribosomal fractionation, cyclin D expression analysis","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (KO mouse, cell rescue, ribosomal fractionation), replicated across cellular and in vivo contexts in a single focused study","pmids":["27829658"],"is_preprint":false},{"year":2018,"finding":"UBA52 (Uba52) is essential for preimplantation embryo development; CRISPR/Cas9-mediated biallelic knockout in porcine embryos causes developmental arrest at the 4-to-8-cell transition (around major zygotic genomic activation), reduces proteasome protein levels, and causes abnormal nuclear morphology.","method":"CRISPR/Cas9 gene editing in porcine oocytes, in vitro fertilization, immunolabeling, western blotting, PCR genotyping","journal":"Biology open","confidence":"High","confidence_rationale":"Tier 2 / Moderate — clean CRISPR KO with defined developmental phenotype and proteasome readout, multiple orthogonal methods, single lab","pmids":["30135083"],"is_preprint":false},{"year":2022,"finding":"UBA52 physically interacts with α-synuclein, HSP90, and E3-ubiquitin ligase CHIP; the lysine-63 residue of UBA52 is required for CHIP-mediated ubiquitylation of HSP90 in vitro. UBA52 co-localizes with α-synuclein in the mitochondrion.","method":"In silico prediction, mass spectrometry, co-immunoprecipitation, in vitro ubiquitylation assay with K63 mutant, immunofluorescence co-localization","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro ubiquitylation with mutagenesis plus reciprocal Co-IP, single lab, multiple orthogonal methods","pmids":["36497031"],"is_preprint":false},{"year":2023,"finding":"UBA52 interacts with mitochondrial outer membrane channel protein VDAC1 and participates in CHIP-mediated ubiquitylation of VDAC1, as shown by mass spectrometry, co-immunoprecipitation, and in vitro ubiquitylation assay. UBA52 overexpression preserves mitochondrial membrane potential, complex I activity, and prevents cytochrome c release and mPTP opening in a Parkinson's disease neuronal model.","method":"Mass spectrometry, co-immunoprecipitation, in vitro ubiquitylation assay, mitochondrial functional assays (JC-1, cytochrome c translocation, calcium uptake, mPTP)","journal":"ACS chemical neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP plus in vitro ubiquitylation, multiple functional readouts, single lab","pmids":["36755387"],"is_preprint":false},{"year":2019,"finding":"Degradation of CCNB1 (cyclin B1) depends on UBA52-mediated ubiquitylation, which in turn requires APC11. Knockdown of APC11 causes G2/M arrest even when UBA52 is overexpressed, placing APC11 downstream of or in concert with UBA52 in CCNB1 degradation for cell cycle progression.","method":"Co-immunoprecipitation, shRNA/siRNA knockdown, overexpression, flow cytometry cell cycle analysis, xenograft tumor assay","journal":"American journal of translational research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epistasis by double KD/OE with clear phenotypic readout and Co-IP, single lab","pmids":["31814919"],"is_preprint":false},{"year":2024,"finding":"SMYD5 trimethylates RPL40 (the C-terminal ribosomal protein encoded by UBA52) at lysine 22 (K22me3); recombinant SMYD5 has robust in vitro methyltransferase activity toward RPL40 K22, active-site mutations ablate this activity, and SMYD5 knockout leads to complete loss of RPL40 K22me3 and reduced translation output with increased ribosome collisions in gastric cancer cells.","method":"Biochemical-proteomics, in vitro methylation assay with recombinant SMYD5, active-site mutagenesis, SMYD5 CRISPR knockout, polysome profiling, ribosome collision assay","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with mutagenesis, KO validation, multiple orthogonal methods, replicated across gastric and hepatocellular carcinoma contexts","pmids":["39048817","39103523"],"is_preprint":false},{"year":2025,"finding":"SMYD5 catalyzes RPL40 K22 trimethylation through recognition of a KXY motif; systematic analysis shows SMYD5 does not methylate histones in vitro, and requires a tyrosine at the +2 position of the target peptide. Loss of SMYD5 in K562 cells causes complete loss of RPL40 K22me3 and decreased polysome levels.","method":"Mass spectrometry-based ribosome methylation profiling, in vitro methylation of synthetic RPL40 using fractionated lysate, recombinant SMYD5 activity assay, active-site mutagenesis, SMYD5 CRISPR KO, polysome analysis, systematic KXY motif analysis","journal":"Cell reports","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro reconstitution with mutagenesis, KO validation, recognition-motif dissection, peer-reviewed replication of preprint findings","pmids":["40184250"],"is_preprint":false},{"year":2023,"finding":"The C-terminal ribosomal fragment L40 (encoded by UBA52) masks the regulatory acidic residues E143/E144 and the nucleosome acidic patch to limit RNF168-nucleosome engagement, thereby antagonizing RNF168-mediated H2A/H2AX ubiquitination at K13/15 and impairing 53BP1 recruitment to DNA damage sites. UBA52 (and UBA80/RPS27A) are recruited to laser-induced DNA damage sites and are required for DNA repair.","method":"Laser micro-irradiation recruitment assay, ectopic expression of C-terminal fragments, RNF168-nucleosome engagement assay, H2A ubiquitination assay, 53BP1 recruitment imaging","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mechanistic domain mapping with multiple functional readouts (ubiquitination, 53BP1 recruitment), single lab","pmids":["37451480"],"is_preprint":false},{"year":2023,"finding":"RPL40 knockdown did not stabilize p53 in U2OS cells and did not block p53 stabilization following actinomycin D-induced ribosome biogenesis inhibition, indicating RPL40 is not required for the ribosomal protein–MDM2–p53 stress-signaling pathway in these cells. However, in MCF7 and LNCaP cells, combined knockdown of RPL40 and RPS27a robustly induced p53. RPL40 knockdown impairs rRNA production in all cell lines tested.","method":"siRNA knockdown, actinomycin D treatment, p53 western blotting, rRNA production assay, multiple cell lines","journal":"Biomolecules","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — clean KD with defined molecular readouts in multiple cell lines; mechanistically informative negative result in U2OS with positive result in other lines","pmids":["37371478"],"is_preprint":false},{"year":2024,"finding":"MLKL physically binds UBA52 under physiological conditions; loss of MLKL prevents USP7-mediated cleavage/processing of UBA52, reducing free ubiquitin levels and thereby decreasing K63-linked polyubiquitination of BECN1 and ULK1, which impairs autophagy in the brain.","method":"Co-immunoprecipitation, mlkl knockout mouse, ubiquitin level measurement, K63-ubiquitination assay, single-nucleus RNA sequencing, behavioral testing","journal":"Autophagy","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP, KO mouse with defined molecular and behavioral phenotype, multiple orthogonal methods, single lab","pmids":["39193909"],"is_preprint":false},{"year":2023,"finding":"UBA52-driven ubiquitination promotes degradation of ferroportin (Fpn) via accelerated ubiquitination triggered by reactive oxygen species at the nerve injury site; hydralazine binds UBA52 and competitively inhibits this interaction, reducing Fpn ubiquitination and protecting neurons from ferroptosis.","method":"In vitro and in vivo ubiquitination assays, competitive binding assay, peripheral nerve injury mouse model, ferroptosis markers, motor function assessment","journal":"Journal of pharmaceutical analysis","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro and in vivo ubiquitination assays with competitive binding mechanistic follow-up, single lab","pmids":["38352945"],"is_preprint":false},{"year":2024,"finding":"UBA52 knockdown induces autophagy through EMC6 in hepatocellular carcinoma cells, suppressing HCC cell growth and metastasis both in vitro and in vivo.","method":"siRNA/shRNA knockdown, CCK-8, colony formation, wound healing, Transwell, xenograft mouse model, bioinformatic autophagy pathway analysis","journal":"Journal of cellular and molecular medicine","confidence":"Low","confidence_rationale":"Tier 3 / Weak — autophagy induction via EMC6 supported by knockdown phenotype and bioinformatic analysis, limited mechanistic detail on direct UBA52-EMC6 interaction, single lab","pmids":["38445807"],"is_preprint":false},{"year":2025,"finding":"ROCK2 competes with UBA52 to bind DRP1, thereby preventing UBA52-mediated K48-linked ubiquitination and proteasomal degradation of DRP1; this ROCK2/UBA52/DRP1 axis drives pemigatinib resistance in cholangiocarcinoma by stabilizing DRP1 to suppress ferroptosis.","method":"Co-immunoprecipitation, ubiquitination assay, siRNA knockdown, overexpression, competitive binding assay, in vitro and in vivo tumor models","journal":"Cell death & disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reciprocal Co-IP plus ubiquitination assay with competitive binding mechanism, in vivo validation, single lab","pmids":["40615369"],"is_preprint":false},{"year":2018,"finding":"UBA52 interacts with influenza A virus PA, PA-N155, and PA-N182 proteins in chicken cells; knockdown of UBA52 significantly decreased H5N1 influenza virus titer and attenuated proinflammatory cytokine production, indicating UBA52 is a host factor required for viral replication.","method":"Immunoprecipitation, mass spectrometry interactome, siRNA knockdown, viral titer assay, cytokine measurement","journal":"Frontiers in microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP/MS identification plus KD with defined viral replication phenotype, single lab","pmids":["29867845"],"is_preprint":false},{"year":2026,"finding":"UBA52 directly promotes ubiquitin-mediated degradation of β-catenin; HOPX directly inhibits the UBA52-β-catenin interaction to stabilize β-catenin and activate Wnt/β-catenin signaling in intestinal stem cells in a high-iron context.","method":"Co-immunoprecipitation, competitive binding assay, ubiquitination assay, Hopx+ ISC lineage tracing, CRC mouse model","journal":"International journal of biological sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP-based competitive binding with ubiquitination assay and in vivo genetic model, single lab","pmids":["42157941"],"is_preprint":false},{"year":2026,"finding":"NUDT7 targets UBA52 for proteasomal degradation, reducing free ubiquitin and blocking UBA52-mediated K11/K27/K48-linked polyubiquitination of SREBF1, thereby stabilizing SREBF1 to enhance lipid droplet formation and create a favorable environment for PRRSV replication.","method":"Co-immunoprecipitation, ubiquitination assay (K11/K27/K48 linkage-specific), proteasome inhibitor assay, siRNA knockdown, lipid droplet staining, viral replication assay","journal":"International journal of biological sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with linkage-specific ubiquitination assay and proteasomal degradation rescue, single lab","pmids":["41608635"],"is_preprint":false},{"year":2026,"finding":"EMMPRIN downregulates UBA52 expression, reducing the free ubiquitin pool and decreasing K63-linked polyubiquitination of monocarboxylate transporter 1 (MCT1), leading to MCT1 destabilization and global increase in protein lactylation.","method":"Proteomic sequencing, mass spectrometry, co-immunoprecipitation, western blotting, K63-linkage ubiquitination assay, EMMPRIN KO/OE mouse and cell models","journal":"Frontiers in pharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP, linkage-specific ubiquitination assay, and KO/OE in vivo and in vitro models, single lab","pmids":["41660506"],"is_preprint":false},{"year":2026,"finding":"UBA52 promotes Daxx ubiquitination and proteasomal degradation; UBA52 overexpression reduces hemin-induced neuronal apoptosis and mitochondrial dysfunction, and this protective effect is abolished by Daxx overexpression, placing Daxx downstream of UBA52.","method":"IP-LC/MS, co-immunoprecipitation, AAV9 overexpression in ICH mouse model, TUNEL assay, JC-1 staining, MitoTracker, caspase-3/9 measurement, rescue experiment with Daxx overexpression","journal":"Molecular neurobiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP/MS identifies interaction, rescue experiment establishes pathway epistasis, in vivo AAV model, single lab","pmids":["41553582"],"is_preprint":false},{"year":2025,"finding":"Sparc physically interacts with UBA52 (identified by immunoprecipitation/mass spectrometry and validated by co-immunoprecipitation) and upregulates UBA52 expression; knockdown of Uba52 abolishes the anti-inflammatory and mitochondrial-protective effects of Sparc overexpression in LPS-stimulated microglial cells.","method":"Immunoprecipitation + mass spectrometry, co-immunoprecipitation, siRNA knockdown, co-culture with neurons, cytokine ELISA, ROS/mitochondrial potential assays","journal":"Frontiers in bioscience (Landmark edition)","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP/MS with KD epistasis in a cell line model, single lab, limited mechanistic detail on direct ubiquitination","pmids":["40917064"],"is_preprint":false},{"year":2025,"finding":"During non-segmented negative-sense viral infection, rpL40 (the ribosomal protein encoded by UBA52) is recruited to a noncanonical site on the small subunit of 80S ribosomes near the mRNA entry site, forming specialized ribosomes that preferentially bind viral mRNAs to enhance viral protein synthesis critical for replication.","method":"Cryo-EM/structural ribosome analysis, ribosome fractionation, viral infection model, mRNA binding assay","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — structural ribosome remodeling evidence with functional viral replication readout, preprint not yet peer-reviewed","pmids":[],"is_preprint":true},{"year":2002,"finding":"The UbA52 promoter contains glucose-responsive E-box sequences and stress response elements (STRE); mutations in the first E-box or STRE reduce promoter activity under high glucose conditions in kidney cells, and UbA52 protein localizes to renal tubules and ribosomal fractions.","method":"Promoter deletion constructs with SEAP reporter, site-directed mutagenesis, primer extension, in situ hybridization, immunohistochemistry, ribosomal fractionation","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — promoter mutagenesis with reporter assay and subcellular fractionation, single lab","pmids":["12171997"],"is_preprint":false}],"current_model":"UBA52 encodes a fusion protein of ubiquitin and ribosomal protein L40 (RPL40); after proteolytic processing by deubiquitinases (including USP7), it simultaneously supplies ubiquitin to the free pool and RPL40 to the ribosome, where RPL40 is trimethylated at K22 by the methyltransferase SMYD5 to regulate translation elongation. UBA52-derived ubiquitin participates in diverse substrate ubiquitination events (including HSP90, VDAC1, CCNB1, Fpn, DRP1, SREBF1, Daxx, and β-catenin) often in concert with specific E3 ligases (e.g., CHIP, APC11), and the L40 ribosomal fragment can also modulate DNA damage signaling by antagonizing RNF168-nucleosome engagement to fine-tune H2A ubiquitination and 53BP1 recruitment."},"narrative":{"mechanistic_narrative":"UBA52 encodes a fusion protein of ubiquitin and the ribosomal protein L40 (RPL40), whose proteolytic separation co-supplies the free ubiquitin pool and the L40 subunit required for ribosome function and protein synthesis; this dual output is essential, as Uba52 deficiency causes embryonic lethality and developmental arrest with reduced proteasome levels [PMID:27829658, PMID:30135083]. The L40 moiety is delivered to the ribosome where it is trimethylated at K22 by the methyltransferase SMYD5 through recognition of a KXY motif, a modification that supports translation elongation and limits ribosome collisions [PMID:39048817, PMID:39103523, PMID:40184250]. UBA52-derived ubiquitin feeds diverse substrate ubiquitination events, frequently acting with specific E3 ligases: the K63 residue of UBA52 enables CHIP-mediated ubiquitylation of HSP90 and the mitochondrial channel VDAC1, with mitochondrial protection in neuronal models [PMID:36497031, PMID:36755387]; UBA52 cooperates with APC11 to drive CCNB1 degradation for cell-cycle progression [PMID:31814919]; and it directs ubiquitin-mediated degradation of substrates including ferroportin, DRP1, SREBF1, Daxx, and β-catenin, processes that are gated by competing binding partners (ROCK2, HOPX) and by regulators of UBA52 abundance or processing (USP7, MLKL, NUDT7) that tune the free ubiquitin available for K11/K27/K48/K63-linked chains [PMID:39193909, PMID:38352945, PMID:40615369, PMID:42157941, PMID:41608635, PMID:41553582]. Independently of its ubiquitin role, the L40 fragment is recruited to DNA damage sites and antagonizes RNF168-nucleosome engagement to fine-tune H2A/H2AX ubiquitination and 53BP1 recruitment [PMID:37451480]. Through these activities UBA52 acts at the intersection of translation, the cell cycle, mitochondrial quality control, autophagy, and DNA damage signaling, and is repeatedly co-opted as a host factor during viral infection [PMID:29867845, PMID:41608635].","teleology":[{"year":2002,"claim":"Established transcriptional control and tissue/subcellular distribution of UBA52, showing it is a glucose- and stress-responsive ribosomal-fraction protein.","evidence":"Promoter deletion/mutagenesis with SEAP reporter, in situ hybridization, immunohistochemistry, and ribosomal fractionation in kidney cells","pmids":["12171997"],"confidence":"Medium","gaps":["Did not address the ubiquitin moiety's role","No connection to specific ubiquitination substrates"]},{"year":2016,"claim":"Resolved whether UBA52's two moieties are functionally separable, showing proteolytic cleavage co-supplies ribosomal L40 and free ubiquitin and that ubiquitin is required for cyclin D/cell-cycle regulation.","evidence":"Uba52-knockout mouse (embryonic lethal), cell-based rescue assays, ribosomal fractionation, cyclin D expression analysis","pmids":["27829658"],"confidence":"High","gaps":["Did not identify the processing protease","Mechanism linking ubiquitin pool to cyclin D not resolved"]},{"year":2018,"claim":"Defined a developmental requirement for UBA52 and linked it to proteasome homeostasis, and separately identified it as a host factor for viral replication.","evidence":"CRISPR/Cas9 biallelic knockout in porcine embryos with proteasome readout (idx1); Co-IP/MS interactome and siRNA knockdown with viral titer assay for influenza A PA (idx13)","pmids":["30135083","29867845"],"confidence":"High","gaps":["Molecular basis of zygotic-activation arrest unknown","Whether viral effect is via ubiquitin supply or direct interaction unresolved"]},{"year":2019,"claim":"Connected UBA52-derived ubiquitin to APC-driven cell-cycle progression by showing CCNB1 degradation requires both UBA52 and APC11.","evidence":"Co-IP, double knockdown/overexpression epistasis, flow cytometry cell-cycle analysis, xenograft assay","pmids":["31814919"],"confidence":"Medium","gaps":["Direct E3-substrate architecture not reconstituted","Single lab"]},{"year":2022,"claim":"Identified specific substrate ubiquitination chemistry, showing the K63 residue of UBA52 is required for CHIP-mediated HSP90 ubiquitylation and that UBA52 co-localizes with α-synuclein at mitochondria.","evidence":"Co-IP, in vitro ubiquitylation with K63 mutant, immunofluorescence co-localization","pmids":["36497031"],"confidence":"Medium","gaps":["Functional consequence of HSP90 ubiquitylation not established","Single lab"]},{"year":2023,"claim":"Extended the CHIP-UBA52 axis to mitochondrial VDAC1 and revealed a moonlighting role of the L40 fragment in DNA damage signaling, plus a role in rRNA production distinct from p53 stress signaling.","evidence":"Co-IP and in vitro ubiquitylation with mitochondrial functional assays (idx3); laser micro-irradiation, RNF168-nucleosome engagement and 53BP1 imaging (idx7); siRNA knockdown with p53 and rRNA readouts across cell lines (idx8)","pmids":["36755387","37451480","37371478"],"confidence":"Medium","gaps":["DNA-damage role tested largely with ectopic fragments","Cell-line-dependent p53 responses not mechanistically unified","Single labs"]},{"year":2023,"claim":"Linked UBA52-driven ubiquitination to ferroptosis through ferroportin degradation and identified a small-molecule (hydralazine) competitive inhibitor of UBA52 binding.","evidence":"In vitro/in vivo ubiquitination assays, competitive binding, peripheral nerve injury mouse model, ferroptosis markers","pmids":["38352945"],"confidence":"Medium","gaps":["Direct E3 ligase for Fpn not defined","Single lab"]},{"year":2024,"claim":"Identified SMYD5 as the methyltransferase that trimethylates RPL40 K22 and tied this modification to translation output and ribosome collision control.","evidence":"In vitro methylation with recombinant SMYD5, active-site mutagenesis, SMYD5 CRISPR KO, polysome profiling, ribosome collision assay across cancer contexts","pmids":["39048817","39103523"],"confidence":"High","gaps":["Translational targets selectively affected not enumerated","Link between K22me3 and elongation kinetics mechanistically partial"]},{"year":2024,"claim":"Showed that processing of UBA52 itself is regulated, with MLKL enabling USP7-mediated cleavage to sustain the free ubiquitin pool and K63-linked ubiquitination of autophagy regulators, and that UBA52 loss can drive autophagy via EMC6.","evidence":"Co-IP, mlkl knockout mouse, ubiquitin/K63 assays, snRNA-seq, behavior (idx9); siRNA/shRNA knockdown with autophagy and tumor phenotypes plus bioinformatics (idx11)","pmids":["39193909","38445807"],"confidence":"Medium","gaps":["EMC6 link lacks direct interaction evidence (Low confidence)","How MLKL controls USP7 access to UBA52 unresolved"]},{"year":2025,"claim":"Dissected the SMYD5 recognition rule (KXY motif, +2 tyrosine) and confirmed it is non-histone-directed, while a preprint proposed L40-remodeled specialized ribosomes that favor viral mRNA translation.","evidence":"MS ribosome methylation profiling, recombinant SMYD5 assays, motif analysis, SMYD5 CRISPR KO, polysome analysis (idx6); cryo-EM ribosome structural analysis with viral mRNA binding (idx19, preprint)","pmids":["40184250"],"confidence":"High","gaps":["Specialized-ribosome model awaits peer review (preprint)","In vivo relevance of viral-mRNA-preferring ribosomes untested"]},{"year":2025,"claim":"Broadened the substrate repertoire and regulatory inputs, showing competition (ROCK2 vs UBA52 for DRP1) and partner-dependent activation (Sparc) that gate UBA52-mediated degradation in disease contexts.","evidence":"Co-IP, K48 ubiquitination and competitive binding assays in cholangiocarcinoma models (idx12); Co-IP/MS and KD epistasis in microglia (idx18)","pmids":["40615369","40917064"],"confidence":"Medium","gaps":["Sparc-UBA52 lacks direct ubiquitination evidence (Low confidence)","How competing partners select substrates not generalized"]},{"year":2026,"claim":"Consolidated UBA52 as a hub whose abundance/free-ubiquitin output controls degradation of β-catenin, SREBF1, Daxx, and MCT1, with upstream regulators (HOPX, NUDT7, EMMPRIN) tuning these effects across stem-cell, lipid-metabolism, neuronal, and lactylation contexts.","evidence":"Co-IP, competitive binding, linkage-specific (K11/K27/K48/K63) ubiquitination assays, proteasome inhibition, and in vivo genetic/AAV models","pmids":["42157941","41608635","41553582","41660506"],"confidence":"Medium","gaps":["Cognate E3 ligases for several substrates not identified","Whether effects reflect direct UBA52 activity or global ubiquitin-pool changes not always separated","Single labs per substrate"]},{"year":null,"claim":"How the ribosomal (L40) and ubiquitin-donor functions of UBA52 are coordinated within a single cell, and what determines substrate and chain-linkage selectivity for UBA52-derived ubiquitin, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model linking translation regulation to substrate-specific ubiquitination","Chain-type selection (K11/K27/K48/K63) mechanism undefined","Cognate E3 ligases for most named substrates unmapped"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0031386","term_label":"protein tag activity","supporting_discovery_ids":[0,2,9]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,5,6]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[2,3,4,12,14]}],"localization":[{"term_id":"GO:0005840","term_label":"ribosome","supporting_discovery_ids":[0,5,6,20]},{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[2,3]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[7]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,5,6]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[0,4]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[7]},{"term_id":"R-HSA-9612973","term_label":"Autophagy","supporting_discovery_ids":[9,11]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[14]}],"complexes":["80S ribosome (L40/RPL40 subunit)"],"partners":["CHIP","HSP90","VDAC1","APC11","MLKL","USP7","DRP1","SMYD5"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P62987","full_name":"Ubiquitin-ribosomal protein eL40 fusion protein","aliases":["CEP52","Ubiquitin A-52 residue ribosomal protein fusion product 1"],"length_aa":128,"mass_kda":14.7,"function":"Exists either covalently attached to another protein, or free (unanchored). When covalently bound, it is conjugated to target proteins via an isopeptide bond either as a monomer (monoubiquitin), a polymer linked via different Lys residues of the ubiquitin (polyubiquitin chains) or a linear polymer linked via the initiator Met of the ubiquitin (linear polyubiquitin chains). Polyubiquitin chains, when attached to a target protein, have different functions depending on the Lys residue of the ubiquitin that is linked: Lys-6-linked may be involved in DNA repair; Lys-11-linked is involved in ERAD (endoplasmic reticulum-associated degradation) and in cell-cycle regulation; Lys-29-linked is involved in proteotoxic stress response and cell cycle; Lys-33-linked is involved in kinase modification; Lys-48-linked is involved in protein degradation via the proteasome; Lys-63-linked is involved in endocytosis, DNA-damage responses as well as in signaling processes leading to activation of the transcription factor NF-kappa-B. Linear polymer chains formed via attachment by the initiator Met lead to cell signaling. Ubiquitin is usually conjugated to Lys residues of target proteins, however, in rare cases, conjugation to Cys or Ser residues has been observed. When polyubiquitin is free (unanchored-polyubiquitin), it also has distinct roles, such as in activation of protein kinases, and in signaling Component of the 60S subunit of the ribosome (PubMed:23169626, PubMed:23636399, PubMed:32669547, PubMed:39048817, PubMed:39103523). Ribosomal protein L40 is essential for translation of a subset of cellular transcripts, and especially for cap-dependent translation of vesicular stomatitis virus mRNAs (PubMed:23169626, PubMed:23636399, PubMed:32669547, PubMed:39048817, PubMed:39103523)","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/P62987/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/UBA52","classification":"Common Essential","n_dependent_lines":1207,"n_total_lines":1208,"dependency_fraction":0.9991721854304636},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000221983","cell_line_id":"CID001031","localizations":[{"compartment":"cytoplasmic","grade":3},{"compartment":"nucleoplasm","grade":3},{"compartment":"nuclear_punctae","grade":2}],"interactors":[{"gene":"RPS27A","stoichiometry":10.0},{"gene":"UBC;UBB;RPS27A;UBA52","stoichiometry":10.0},{"gene":"PSMA6","stoichiometry":0.2},{"gene":"PSMD12","stoichiometry":0.2},{"gene":"TOP2A","stoichiometry":0.2},{"gene":"NPLOC4","stoichiometry":0.2},{"gene":"HUWE1","stoichiometry":0.2},{"gene":"CCAR2","stoichiometry":0.2},{"gene":"PSMC1","stoichiometry":0.2},{"gene":"PSMC5","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID001031","total_profiled":1310},"omim":[{"mim_id":"614792","title":"TRANSMEMBRANE AND UBIQUITIN-LIKE DOMAIN-CONTAINING PROTEIN 1; TMUB1","url":"https://www.omim.org/entry/614792"},{"mim_id":"191343","title":"RIBOSOMAL PROTEIN S27a; RPS27A","url":"https://www.omim.org/entry/191343"},{"mim_id":"191339","title":"UBIQUITIN B; UBB","url":"https://www.omim.org/entry/191339"},{"mim_id":"191321","title":"UBIQUITIN A-52-RESIDUE RIBOSOMAL PROTEIN FUSION PRODUCT; UBA52","url":"https://www.omim.org/entry/191321"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Cytosol","reliability":"Approved"},{"location":"Nucleoplasm","reliability":"Additional"},{"location":"Endoplasmic reticulum","reliability":"Additional"},{"location":"Plasma membrane","reliability":"Additional"},{"location":"Acrosome","reliability":"Additional"},{"location":"Equatorial segment","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in 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AGENT","date":"2024-08-01","source":"bioRxiv","url":"https://doi.org/10.1101/2024.07.30.605947","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":21565,"output_tokens":5411,"usd":0.07293,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":13843,"output_tokens":4557,"usd":0.09157,"stage2_stop_reason":"end_turn"},"total_usd":0.1645,"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\": 2016,\n      \"finding\": \"UBA52 encodes a fusion protein of ubiquitin and ribosomal protein L40 (RPL40); proteolytic cleavage of RPL40 from UBA52 is required for maintaining protein synthesis, and RPL40 forms a ribosomal complex with ubiquitin co-supplied by UBA52. Expression of RPL40 alone (without the ubiquitin moiety) is insufficient to regulate cyclin D expression or rescue cell-cycle arrest caused by UBA52 deficiency.\",\n      \"method\": \"Knockout mouse model (Uba52-deficient embryonic lethality), cell-based overexpression/rescue assays, ribosomal fractionation, cyclin D expression analysis\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (KO mouse, cell rescue, ribosomal fractionation), replicated across cellular and in vivo contexts in a single focused study\",\n      \"pmids\": [\"27829658\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"UBA52 (Uba52) is essential for preimplantation embryo development; CRISPR/Cas9-mediated biallelic knockout in porcine embryos causes developmental arrest at the 4-to-8-cell transition (around major zygotic genomic activation), reduces proteasome protein levels, and causes abnormal nuclear morphology.\",\n      \"method\": \"CRISPR/Cas9 gene editing in porcine oocytes, in vitro fertilization, immunolabeling, western blotting, PCR genotyping\",\n      \"journal\": \"Biology open\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean CRISPR KO with defined developmental phenotype and proteasome readout, multiple orthogonal methods, single lab\",\n      \"pmids\": [\"30135083\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"UBA52 physically interacts with α-synuclein, HSP90, and E3-ubiquitin ligase CHIP; the lysine-63 residue of UBA52 is required for CHIP-mediated ubiquitylation of HSP90 in vitro. UBA52 co-localizes with α-synuclein in the mitochondrion.\",\n      \"method\": \"In silico prediction, mass spectrometry, co-immunoprecipitation, in vitro ubiquitylation assay with K63 mutant, immunofluorescence co-localization\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro ubiquitylation with mutagenesis plus reciprocal Co-IP, single lab, multiple orthogonal methods\",\n      \"pmids\": [\"36497031\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"UBA52 interacts with mitochondrial outer membrane channel protein VDAC1 and participates in CHIP-mediated ubiquitylation of VDAC1, as shown by mass spectrometry, co-immunoprecipitation, and in vitro ubiquitylation assay. UBA52 overexpression preserves mitochondrial membrane potential, complex I activity, and prevents cytochrome c release and mPTP opening in a Parkinson's disease neuronal model.\",\n      \"method\": \"Mass spectrometry, co-immunoprecipitation, in vitro ubiquitylation assay, mitochondrial functional assays (JC-1, cytochrome c translocation, calcium uptake, mPTP)\",\n      \"journal\": \"ACS chemical neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP plus in vitro ubiquitylation, multiple functional readouts, single lab\",\n      \"pmids\": [\"36755387\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Degradation of CCNB1 (cyclin B1) depends on UBA52-mediated ubiquitylation, which in turn requires APC11. Knockdown of APC11 causes G2/M arrest even when UBA52 is overexpressed, placing APC11 downstream of or in concert with UBA52 in CCNB1 degradation for cell cycle progression.\",\n      \"method\": \"Co-immunoprecipitation, shRNA/siRNA knockdown, overexpression, flow cytometry cell cycle analysis, xenograft tumor assay\",\n      \"journal\": \"American journal of translational research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epistasis by double KD/OE with clear phenotypic readout and Co-IP, single lab\",\n      \"pmids\": [\"31814919\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"SMYD5 trimethylates RPL40 (the C-terminal ribosomal protein encoded by UBA52) at lysine 22 (K22me3); recombinant SMYD5 has robust in vitro methyltransferase activity toward RPL40 K22, active-site mutations ablate this activity, and SMYD5 knockout leads to complete loss of RPL40 K22me3 and reduced translation output with increased ribosome collisions in gastric cancer cells.\",\n      \"method\": \"Biochemical-proteomics, in vitro methylation assay with recombinant SMYD5, active-site mutagenesis, SMYD5 CRISPR knockout, polysome profiling, ribosome collision assay\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with mutagenesis, KO validation, multiple orthogonal methods, replicated across gastric and hepatocellular carcinoma contexts\",\n      \"pmids\": [\"39048817\", \"39103523\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"SMYD5 catalyzes RPL40 K22 trimethylation through recognition of a KXY motif; systematic analysis shows SMYD5 does not methylate histones in vitro, and requires a tyrosine at the +2 position of the target peptide. Loss of SMYD5 in K562 cells causes complete loss of RPL40 K22me3 and decreased polysome levels.\",\n      \"method\": \"Mass spectrometry-based ribosome methylation profiling, in vitro methylation of synthetic RPL40 using fractionated lysate, recombinant SMYD5 activity assay, active-site mutagenesis, SMYD5 CRISPR KO, polysome analysis, systematic KXY motif analysis\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro reconstitution with mutagenesis, KO validation, recognition-motif dissection, peer-reviewed replication of preprint findings\",\n      \"pmids\": [\"40184250\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"The C-terminal ribosomal fragment L40 (encoded by UBA52) masks the regulatory acidic residues E143/E144 and the nucleosome acidic patch to limit RNF168-nucleosome engagement, thereby antagonizing RNF168-mediated H2A/H2AX ubiquitination at K13/15 and impairing 53BP1 recruitment to DNA damage sites. UBA52 (and UBA80/RPS27A) are recruited to laser-induced DNA damage sites and are required for DNA repair.\",\n      \"method\": \"Laser micro-irradiation recruitment assay, ectopic expression of C-terminal fragments, RNF168-nucleosome engagement assay, H2A ubiquitination assay, 53BP1 recruitment imaging\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mechanistic domain mapping with multiple functional readouts (ubiquitination, 53BP1 recruitment), single lab\",\n      \"pmids\": [\"37451480\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"RPL40 knockdown did not stabilize p53 in U2OS cells and did not block p53 stabilization following actinomycin D-induced ribosome biogenesis inhibition, indicating RPL40 is not required for the ribosomal protein–MDM2–p53 stress-signaling pathway in these cells. However, in MCF7 and LNCaP cells, combined knockdown of RPL40 and RPS27a robustly induced p53. RPL40 knockdown impairs rRNA production in all cell lines tested.\",\n      \"method\": \"siRNA knockdown, actinomycin D treatment, p53 western blotting, rRNA production assay, multiple cell lines\",\n      \"journal\": \"Biomolecules\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — clean KD with defined molecular readouts in multiple cell lines; mechanistically informative negative result in U2OS with positive result in other lines\",\n      \"pmids\": [\"37371478\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"MLKL physically binds UBA52 under physiological conditions; loss of MLKL prevents USP7-mediated cleavage/processing of UBA52, reducing free ubiquitin levels and thereby decreasing K63-linked polyubiquitination of BECN1 and ULK1, which impairs autophagy in the brain.\",\n      \"method\": \"Co-immunoprecipitation, mlkl knockout mouse, ubiquitin level measurement, K63-ubiquitination assay, single-nucleus RNA sequencing, behavioral testing\",\n      \"journal\": \"Autophagy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP, KO mouse with defined molecular and behavioral phenotype, multiple orthogonal methods, single lab\",\n      \"pmids\": [\"39193909\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"UBA52-driven ubiquitination promotes degradation of ferroportin (Fpn) via accelerated ubiquitination triggered by reactive oxygen species at the nerve injury site; hydralazine binds UBA52 and competitively inhibits this interaction, reducing Fpn ubiquitination and protecting neurons from ferroptosis.\",\n      \"method\": \"In vitro and in vivo ubiquitination assays, competitive binding assay, peripheral nerve injury mouse model, ferroptosis markers, motor function assessment\",\n      \"journal\": \"Journal of pharmaceutical analysis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro and in vivo ubiquitination assays with competitive binding mechanistic follow-up, single lab\",\n      \"pmids\": [\"38352945\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"UBA52 knockdown induces autophagy through EMC6 in hepatocellular carcinoma cells, suppressing HCC cell growth and metastasis both in vitro and in vivo.\",\n      \"method\": \"siRNA/shRNA knockdown, CCK-8, colony formation, wound healing, Transwell, xenograft mouse model, bioinformatic autophagy pathway analysis\",\n      \"journal\": \"Journal of cellular and molecular medicine\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — autophagy induction via EMC6 supported by knockdown phenotype and bioinformatic analysis, limited mechanistic detail on direct UBA52-EMC6 interaction, single lab\",\n      \"pmids\": [\"38445807\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ROCK2 competes with UBA52 to bind DRP1, thereby preventing UBA52-mediated K48-linked ubiquitination and proteasomal degradation of DRP1; this ROCK2/UBA52/DRP1 axis drives pemigatinib resistance in cholangiocarcinoma by stabilizing DRP1 to suppress ferroptosis.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay, siRNA knockdown, overexpression, competitive binding assay, in vitro and in vivo tumor models\",\n      \"journal\": \"Cell death & disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reciprocal Co-IP plus ubiquitination assay with competitive binding mechanism, in vivo validation, single lab\",\n      \"pmids\": [\"40615369\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"UBA52 interacts with influenza A virus PA, PA-N155, and PA-N182 proteins in chicken cells; knockdown of UBA52 significantly decreased H5N1 influenza virus titer and attenuated proinflammatory cytokine production, indicating UBA52 is a host factor required for viral replication.\",\n      \"method\": \"Immunoprecipitation, mass spectrometry interactome, siRNA knockdown, viral titer assay, cytokine measurement\",\n      \"journal\": \"Frontiers in microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP/MS identification plus KD with defined viral replication phenotype, single lab\",\n      \"pmids\": [\"29867845\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"UBA52 directly promotes ubiquitin-mediated degradation of β-catenin; HOPX directly inhibits the UBA52-β-catenin interaction to stabilize β-catenin and activate Wnt/β-catenin signaling in intestinal stem cells in a high-iron context.\",\n      \"method\": \"Co-immunoprecipitation, competitive binding assay, ubiquitination assay, Hopx+ ISC lineage tracing, CRC mouse model\",\n      \"journal\": \"International journal of biological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP-based competitive binding with ubiquitination assay and in vivo genetic model, single lab\",\n      \"pmids\": [\"42157941\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"NUDT7 targets UBA52 for proteasomal degradation, reducing free ubiquitin and blocking UBA52-mediated K11/K27/K48-linked polyubiquitination of SREBF1, thereby stabilizing SREBF1 to enhance lipid droplet formation and create a favorable environment for PRRSV replication.\",\n      \"method\": \"Co-immunoprecipitation, ubiquitination assay (K11/K27/K48 linkage-specific), proteasome inhibitor assay, siRNA knockdown, lipid droplet staining, viral replication assay\",\n      \"journal\": \"International journal of biological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with linkage-specific ubiquitination assay and proteasomal degradation rescue, single lab\",\n      \"pmids\": [\"41608635\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"EMMPRIN downregulates UBA52 expression, reducing the free ubiquitin pool and decreasing K63-linked polyubiquitination of monocarboxylate transporter 1 (MCT1), leading to MCT1 destabilization and global increase in protein lactylation.\",\n      \"method\": \"Proteomic sequencing, mass spectrometry, co-immunoprecipitation, western blotting, K63-linkage ubiquitination assay, EMMPRIN KO/OE mouse and cell models\",\n      \"journal\": \"Frontiers in pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP, linkage-specific ubiquitination assay, and KO/OE in vivo and in vitro models, single lab\",\n      \"pmids\": [\"41660506\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"UBA52 promotes Daxx ubiquitination and proteasomal degradation; UBA52 overexpression reduces hemin-induced neuronal apoptosis and mitochondrial dysfunction, and this protective effect is abolished by Daxx overexpression, placing Daxx downstream of UBA52.\",\n      \"method\": \"IP-LC/MS, co-immunoprecipitation, AAV9 overexpression in ICH mouse model, TUNEL assay, JC-1 staining, MitoTracker, caspase-3/9 measurement, rescue experiment with Daxx overexpression\",\n      \"journal\": \"Molecular neurobiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP/MS identifies interaction, rescue experiment establishes pathway epistasis, in vivo AAV model, single lab\",\n      \"pmids\": [\"41553582\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Sparc physically interacts with UBA52 (identified by immunoprecipitation/mass spectrometry and validated by co-immunoprecipitation) and upregulates UBA52 expression; knockdown of Uba52 abolishes the anti-inflammatory and mitochondrial-protective effects of Sparc overexpression in LPS-stimulated microglial cells.\",\n      \"method\": \"Immunoprecipitation + mass spectrometry, co-immunoprecipitation, siRNA knockdown, co-culture with neurons, cytokine ELISA, ROS/mitochondrial potential assays\",\n      \"journal\": \"Frontiers in bioscience (Landmark edition)\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP/MS with KD epistasis in a cell line model, single lab, limited mechanistic detail on direct ubiquitination\",\n      \"pmids\": [\"40917064\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"During non-segmented negative-sense viral infection, rpL40 (the ribosomal protein encoded by UBA52) is recruited to a noncanonical site on the small subunit of 80S ribosomes near the mRNA entry site, forming specialized ribosomes that preferentially bind viral mRNAs to enhance viral protein synthesis critical for replication.\",\n      \"method\": \"Cryo-EM/structural ribosome analysis, ribosome fractionation, viral infection model, mRNA binding assay\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — structural ribosome remodeling evidence with functional viral replication readout, preprint not yet peer-reviewed\",\n      \"pmids\": [],\n      \"is_preprint\": true\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"The UbA52 promoter contains glucose-responsive E-box sequences and stress response elements (STRE); mutations in the first E-box or STRE reduce promoter activity under high glucose conditions in kidney cells, and UbA52 protein localizes to renal tubules and ribosomal fractions.\",\n      \"method\": \"Promoter deletion constructs with SEAP reporter, site-directed mutagenesis, primer extension, in situ hybridization, immunohistochemistry, ribosomal fractionation\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — promoter mutagenesis with reporter assay and subcellular fractionation, single lab\",\n      \"pmids\": [\"12171997\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"UBA52 encodes a fusion protein of ubiquitin and ribosomal protein L40 (RPL40); after proteolytic processing by deubiquitinases (including USP7), it simultaneously supplies ubiquitin to the free pool and RPL40 to the ribosome, where RPL40 is trimethylated at K22 by the methyltransferase SMYD5 to regulate translation elongation. UBA52-derived ubiquitin participates in diverse substrate ubiquitination events (including HSP90, VDAC1, CCNB1, Fpn, DRP1, SREBF1, Daxx, and β-catenin) often in concert with specific E3 ligases (e.g., CHIP, APC11), and the L40 ribosomal fragment can also modulate DNA damage signaling by antagonizing RNF168-nucleosome engagement to fine-tune H2A ubiquitination and 53BP1 recruitment.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"UBA52 encodes a fusion protein of ubiquitin and the ribosomal protein L40 (RPL40), whose proteolytic separation co-supplies the free ubiquitin pool and the L40 subunit required for ribosome function and protein synthesis; this dual output is essential, as Uba52 deficiency causes embryonic lethality and developmental arrest with reduced proteasome levels [#0, #1]. The L40 moiety is delivered to the ribosome where it is trimethylated at K22 by the methyltransferase SMYD5 through recognition of a KXY motif, a modification that supports translation elongation and limits ribosome collisions [#5, #6]. UBA52-derived ubiquitin feeds diverse substrate ubiquitination events, frequently acting with specific E3 ligases: the K63 residue of UBA52 enables CHIP-mediated ubiquitylation of HSP90 and the mitochondrial channel VDAC1, with mitochondrial protection in neuronal models [#2, #3]; UBA52 cooperates with APC11 to drive CCNB1 degradation for cell-cycle progression [#4]; and it directs ubiquitin-mediated degradation of substrates including ferroportin, DRP1, SREBF1, Daxx, and \\u03b2-catenin, processes that are gated by competing binding partners (ROCK2, HOPX) and by regulators of UBA52 abundance or processing (USP7, MLKL, NUDT7) that tune the free ubiquitin available for K11/K27/K48/K63-linked chains [#9, #10, #12, #14, #15, #17]. Independently of its ubiquitin role, the L40 fragment is recruited to DNA damage sites and antagonizes RNF168-nucleosome engagement to fine-tune H2A/H2AX ubiquitination and 53BP1 recruitment [#7]. Through these activities UBA52 acts at the intersection of translation, the cell cycle, mitochondrial quality control, autophagy, and DNA damage signaling, and is repeatedly co-opted as a host factor during viral infection [#13, #15].\",\n  \"teleology\": [\n    {\n      \"year\": 2002,\n      \"claim\": \"Established transcriptional control and tissue/subcellular distribution of UBA52, showing it is a glucose- and stress-responsive ribosomal-fraction protein.\",\n      \"evidence\": \"Promoter deletion/mutagenesis with SEAP reporter, in situ hybridization, immunohistochemistry, and ribosomal fractionation in kidney cells\",\n      \"pmids\": [\"12171997\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not address the ubiquitin moiety's role\", \"No connection to specific ubiquitination substrates\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Resolved whether UBA52's two moieties are functionally separable, showing proteolytic cleavage co-supplies ribosomal L40 and free ubiquitin and that ubiquitin is required for cyclin D/cell-cycle regulation.\",\n      \"evidence\": \"Uba52-knockout mouse (embryonic lethal), cell-based rescue assays, ribosomal fractionation, cyclin D expression analysis\",\n      \"pmids\": [\"27829658\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not identify the processing protease\", \"Mechanism linking ubiquitin pool to cyclin D not resolved\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Defined a developmental requirement for UBA52 and linked it to proteasome homeostasis, and separately identified it as a host factor for viral replication.\",\n      \"evidence\": \"CRISPR/Cas9 biallelic knockout in porcine embryos with proteasome readout (idx1); Co-IP/MS interactome and siRNA knockdown with viral titer assay for influenza A PA (idx13)\",\n      \"pmids\": [\"30135083\", \"29867845\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of zygotic-activation arrest unknown\", \"Whether viral effect is via ubiquitin supply or direct interaction unresolved\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Connected UBA52-derived ubiquitin to APC-driven cell-cycle progression by showing CCNB1 degradation requires both UBA52 and APC11.\",\n      \"evidence\": \"Co-IP, double knockdown/overexpression epistasis, flow cytometry cell-cycle analysis, xenograft assay\",\n      \"pmids\": [\"31814919\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct E3-substrate architecture not reconstituted\", \"Single lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified specific substrate ubiquitination chemistry, showing the K63 residue of UBA52 is required for CHIP-mediated HSP90 ubiquitylation and that UBA52 co-localizes with \\u03b1-synuclein at mitochondria.\",\n      \"evidence\": \"Co-IP, in vitro ubiquitylation with K63 mutant, immunofluorescence co-localization\",\n      \"pmids\": [\"36497031\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional consequence of HSP90 ubiquitylation not established\", \"Single lab\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Extended the CHIP-UBA52 axis to mitochondrial VDAC1 and revealed a moonlighting role of the L40 fragment in DNA damage signaling, plus a role in rRNA production distinct from p53 stress signaling.\",\n      \"evidence\": \"Co-IP and in vitro ubiquitylation with mitochondrial functional assays (idx3); laser micro-irradiation, RNF168-nucleosome engagement and 53BP1 imaging (idx7); siRNA knockdown with p53 and rRNA readouts across cell lines (idx8)\",\n      \"pmids\": [\"36755387\", \"37451480\", \"37371478\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"DNA-damage role tested largely with ectopic fragments\", \"Cell-line-dependent p53 responses not mechanistically unified\", \"Single labs\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Linked UBA52-driven ubiquitination to ferroptosis through ferroportin degradation and identified a small-molecule (hydralazine) competitive inhibitor of UBA52 binding.\",\n      \"evidence\": \"In vitro/in vivo ubiquitination assays, competitive binding, peripheral nerve injury mouse model, ferroptosis markers\",\n      \"pmids\": [\"38352945\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct E3 ligase for Fpn not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identified SMYD5 as the methyltransferase that trimethylates RPL40 K22 and tied this modification to translation output and ribosome collision control.\",\n      \"evidence\": \"In vitro methylation with recombinant SMYD5, active-site mutagenesis, SMYD5 CRISPR KO, polysome profiling, ribosome collision assay across cancer contexts\",\n      \"pmids\": [\"39048817\", \"39103523\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Translational targets selectively affected not enumerated\", \"Link between K22me3 and elongation kinetics mechanistically partial\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Showed that processing of UBA52 itself is regulated, with MLKL enabling USP7-mediated cleavage to sustain the free ubiquitin pool and K63-linked ubiquitination of autophagy regulators, and that UBA52 loss can drive autophagy via EMC6.\",\n      \"evidence\": \"Co-IP, mlkl knockout mouse, ubiquitin/K63 assays, snRNA-seq, behavior (idx9); siRNA/shRNA knockdown with autophagy and tumor phenotypes plus bioinformatics (idx11)\",\n      \"pmids\": [\"39193909\", \"38445807\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"EMC6 link lacks direct interaction evidence (Low confidence)\", \"How MLKL controls USP7 access to UBA52 unresolved\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Dissected the SMYD5 recognition rule (KXY motif, +2 tyrosine) and confirmed it is non-histone-directed, while a preprint proposed L40-remodeled specialized ribosomes that favor viral mRNA translation.\",\n      \"evidence\": \"MS ribosome methylation profiling, recombinant SMYD5 assays, motif analysis, SMYD5 CRISPR KO, polysome analysis (idx6); cryo-EM ribosome structural analysis with viral mRNA binding (idx19, preprint)\",\n      \"pmids\": [\"40184250\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specialized-ribosome model awaits peer review (preprint)\", \"In vivo relevance of viral-mRNA-preferring ribosomes untested\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Broadened the substrate repertoire and regulatory inputs, showing competition (ROCK2 vs UBA52 for DRP1) and partner-dependent activation (Sparc) that gate UBA52-mediated degradation in disease contexts.\",\n      \"evidence\": \"Co-IP, K48 ubiquitination and competitive binding assays in cholangiocarcinoma models (idx12); Co-IP/MS and KD epistasis in microglia (idx18)\",\n      \"pmids\": [\"40615369\", \"40917064\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Sparc-UBA52 lacks direct ubiquitination evidence (Low confidence)\", \"How competing partners select substrates not generalized\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Consolidated UBA52 as a hub whose abundance/free-ubiquitin output controls degradation of \\u03b2-catenin, SREBF1, Daxx, and MCT1, with upstream regulators (HOPX, NUDT7, EMMPRIN) tuning these effects across stem-cell, lipid-metabolism, neuronal, and lactylation contexts.\",\n      \"evidence\": \"Co-IP, competitive binding, linkage-specific (K11/K27/K48/K63) ubiquitination assays, proteasome inhibition, and in vivo genetic/AAV models\",\n      \"pmids\": [\"42157941\", \"41608635\", \"41553582\", \"41660506\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cognate E3 ligases for several substrates not identified\", \"Whether effects reflect direct UBA52 activity or global ubiquitin-pool changes not always separated\", \"Single labs per substrate\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the ribosomal (L40) and ubiquitin-donor functions of UBA52 are coordinated within a single cell, and what determines substrate and chain-linkage selectivity for UBA52-derived ubiquitin, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model linking translation regulation to substrate-specific ubiquitination\", \"Chain-type selection (K11/K27/K48/K63) mechanism undefined\", \"Cognate E3 ligases for most named substrates unmapped\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0031386\", \"supporting_discovery_ids\": [0, 2, 9]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 5, 6]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [2, 3, 4, 12, 14]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005840\", \"supporting_discovery_ids\": [0, 5, 6, 20]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 5, 6]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [0, 4]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [7]},\n      {\"term_id\": \"R-HSA-9612973\", \"supporting_discovery_ids\": [9, 11]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [14]}\n    ],\n    \"complexes\": [\"80S ribosome (L40/RPL40 subunit)\"],\n    \"partners\": [\"CHIP\", \"HSP90\", \"VDAC1\", \"APC11\", \"MLKL\", \"USP7\", \"DRP1\", \"SMYD5\"],\n    \"other_free_text\": []\n  }\n}\n```","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":5,"faith_total":5,"faith_pct":100.0}}