{"gene":"PSMB4","run_date":"2026-06-10T06:43:36","timeline":{"discoveries":[{"year":2005,"finding":"The E3 ubiquitin ligase SNEV (senescence evasion factor) directly binds to PSMB4, the β7 subunit of the 20S proteasome, physically linking the ubiquitin-proteasome system to the spliceosome. Upon proteasome inhibition, SNEV co-localization with PSMB4 increases, and SNEV co-localizes with ubiquitin without itself being ubiquitinated, suggesting SNEV escorts substrates to the proteasome via this interaction. The yeast homologue of SNEV (Prp19) also interacts with the yeast β7 subunit, indicating evolutionary conservation.","method":"Co-immunoprecipitation, yeast two-hybrid, immunofluorescence microscopy, proteasome inhibition experiments","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, yeast two-hybrid, immunofluorescence with proteasome inhibitor, replicated across yeast and mammalian systems in one study with multiple orthogonal methods","pmids":["15660529"],"is_preprint":false},{"year":2014,"finding":"PSMB4 was identified as the first proteasomal subunit with oncogenic properties: RNAi-mediated loss-of-function reduced cancer cell survival across a panel of 32 cancer cell lines, and functional assays demonstrated PSMB4 is necessary for tumor cell survival and tumor growth in vivo.","method":"RNAi loss-of-function screen across 32 cancer cell lines, in vivo xenograft tumor growth assays","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Strong — large-scale RNAi screen followed by in vivo validation, multiple cell lines and orthogonal readouts","pmids":["24755469"],"is_preprint":false},{"year":2015,"finding":"PSMB4 overexpression in multiple myeloma cells activates NF-κB signaling and upregulates miR-21, promoting cell growth and colony formation. PSMB4 knockdown suppresses NF-κB activity and miR-21 expression. Re-expression of miR-21 rescues the growth suppression caused by PSMB4 knockdown, placing PSMB4 upstream of NF-κB–miR-21 in a proliferative signaling axis.","method":"Ectopic overexpression and siRNA knockdown, NF-κB reporter assays, miRNA expression analysis, rescue experiments with miR-21 re-expression","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss- and gain-of-function with rescue experiment in a single lab, multiple readouts but no structural or in vitro biochemical confirmation of direct NF-κB activation mechanism","pmids":["25656574"],"is_preprint":false},{"year":2015,"finding":"PSMB4 knockdown by siRNA in a neuroinflammation model reduces the upregulation of active caspase-3, cyclin D1, and CDK4 in cortical primary neurons, indicating PSMB4 contributes to neuronal apoptosis downstream of LPS-induced neuroinflammation via these apoptosis- and cell-cycle-related proteins.","method":"siRNA knockdown in primary neurons and rat LPS neuroinflammation model, western blotting, immunohistochemistry","journal":"Journal of molecular histology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — loss-of-function with specific molecular readouts in a single lab, single method set","pmids":["26282113"],"is_preprint":false},{"year":2016,"finding":"PSMB4 expression is upregulated in neurons after spinal cord injury, co-localizing with RIP3-positive neurons. Overexpression and knockdown of PSMB4 modulates RIP3 and MLKL levels in a TNF-α-induced necroptosis cell model, implicating PSMB4 in regulation of the RIP3/MLKL necroptosis pathway.","method":"Western blot, immunohistochemistry, immunofluorescence staining, PSMB4 overexpression and knockdown in necroptosis cell model","journal":"Neurochemical research","confidence":"Low","confidence_rationale":"Tier 3 / Weak — single lab, indirect pathway placement based on co-localization and expression changes without direct biochemical interaction data","pmids":["27514644"],"is_preprint":false},{"year":2018,"finding":"PSMB4 knockdown in glioblastoma cells decreases proliferation, migration, and invasion, induces cell cycle arrest and apoptosis, and reduces expression of phosphorylated focal adhesion kinase (pFAK) and matrix metallopeptidase 9 (MMP9) in vivo, identifying these as downstream effectors of PSMB4-driven invasion.","method":"siRNA knockdown, MTT assay, Annexin V/PI flow cytometry, wound healing and Transwell invasion assays, western blotting, orthotopic xenograft mouse model","journal":"Cellular physiology and biochemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function confirmed in vitro and in vivo with multiple orthogonal functional readouts in a single lab","pmids":["29414809"],"is_preprint":false},{"year":2019,"finding":"FoxM1, a master regulator of cell division, directly binds to the promoter region of PSMB4 and transcriptionally activates PSMB4 expression. Loss-of-function and rescue experiments confirm PSMB4 is required downstream of FoxM1 to drive cervical cancer cell proliferation, establishing a FoxM1–PSMB4 transcriptional axis.","method":"ChIP/promoter binding assay, siRNA knockdown, overexpression, rescue experiments, TCGA correlation analysis","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct promoter binding demonstrated, loss-of-function with rescue in single lab, multiple orthogonal methods","pmids":["31699366"],"is_preprint":false},{"year":2020,"finding":"Bassoon (Bsn), a presynaptic scaffolding protein, directly interacts with PSMB4 (β7 subunit of 20S core proteasome) via three independent interaction interfaces. Expression of PSMB4-interacting fragments of bassoon in cell lines or primary neurons attenuates all endopeptidase activities of cellular proteasome and induces accumulation of ubiquitinated and non-ubiquitinated proteasomal substrates, likely through steric interference with 20S core assembly. Bassoon knockout mice show increased proteasomal activity and depletion of synaptic proteasomal substrates, which is reversed by expressing PSMB4-interacting bassoon fragments.","method":"Co-immunoprecipitation, deletion mapping of interaction interfaces, proteasome activity assays, bassoon knockout mouse brains (synaptic fractionation), primary neuron expression experiments, substrate accumulation assays","journal":"Cellular and molecular life sciences : CMLS","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — direct interaction mapped to three interfaces, in-cell proteasome activity assays, genetic KO rescue with mechanistic specificity, multiple orthogonal methods in one rigorous study","pmids":["32651614"],"is_preprint":false},{"year":2021,"finding":"PSMB4 directly interacts with IκBα and promotes its proteasome-dependent degradation, thereby activating NF-κB signaling and inhibiting cardiomyocyte apoptosis during hypoxia/reoxygenation injury. PSMB4 silence increases IκBα levels and suppresses NF-κB activation, while PSMB4 overexpression has opposite effects.","method":"Co-immunoprecipitation (PSMB4–IκBα interaction), siRNA knockdown and overexpression in neonatal cardiomyocyte H/R model, NF-κB activation assays, western blotting for IκBα and apoptosis markers","journal":"Journal of molecular histology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP identifies IκBα as binding partner, gain- and loss-of-function with mechanistic readouts, single lab","pmids":["33954843"],"is_preprint":false},{"year":2022,"finding":"PSMB4 physically interacts with influenza A virus NS1 protein (interaction mapped by yeast two-hybrid and confirmed by Co-IP and confocal microscopy in mammalian cells). PSMB4 reduces NS1 protein levels, especially in the presence of proteasome inhibitor MG132, and suppresses NS1 functions including interferon inhibition and transient gene expression enhancement. PSMB4 knockdown enhances IAV replication while overexpression attenuates it.","method":"Yeast two-hybrid screening (binding domain mapping), co-immunoprecipitation, confocal microscopy, NS1 protein level assays with MG132, IAV replication assays with knockdown/overexpression","journal":"Viruses","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — interaction confirmed by two orthogonal methods with domain mapping, functional consequence on viral replication shown by gain- and loss-of-function, single lab","pmids":["36298834"],"is_preprint":false},{"year":2023,"finding":"PSMB4 interacts with PRRSV Nsp1α protein; the PCPα domain (aa 66–166) of Nsp1α and the C-terminal domain (aa 250–264) of PSMB4 are critical for this interaction. PSMB4 mediates K63-linked ubiquitination of Nsp1α at K169, targeting Nsp1α for autolysosomal degradation by interacting with LC3 to enhance lysosomal pathway activation. PSMB4 also activates NF-κB signaling to induce type I interferon production by downregulating IκBα and p-IκBα expression, thereby restricting PRRSV replication.","method":"Yeast two-hybrid screening, co-immunoprecipitation, GST pulldown, laser confocal microscopy, ubiquitination assays (K63-linkage), autolysosome pathway assays, NF-κB signaling assays, PSMB4 overexpression and knockdown with PRRSV replication readouts","journal":"Journal of virology","confidence":"High","confidence_rationale":"Tier 1–2 / Strong — interaction confirmed by three orthogonal methods, domain mapping, specific ubiquitination site identified (K169), mechanistic pathway (autolysosome + NF-κB/IFN) established with multiple functional assays in one study","pmids":["36943051"],"is_preprint":false},{"year":2024,"finding":"PSMB4 knockdown in bladder cancer cells reduces expression of phosphorylated FAK and myosin light chain (MLC), leading to decreased cancer cell migration. PSMB4 suppression also decreases VEGF-B levels, reducing angiogenic capacity and lowering VEGFR2 expression in HUVECs. In vivo metastatic models show PSMB4 knockdown reduces lung tumor volumes.","method":"siRNA knockdown, western blotting (pFAK, MLC, VEGF-B, VEGFR2), migration/angiogenesis assays, in vivo metastatic mouse model","journal":"International journal of molecular sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — loss-of-function with specific downstream molecular targets identified, in vitro and in vivo validation, single lab","pmids":["38791597"],"is_preprint":false},{"year":2025,"finding":"S146 and M148 within the mature chain domain of PSMB4 are critical residues for binding and degrading PRRSV nsp1α. Truncated mutant assays and structure prediction showed these residues mediate the PSMB4–nsp1α interaction, and PSMB4 overexpression reduces nsp1α and viral N protein levels in a dose-dependent manner while knockdown promotes PRRSV replication.","method":"Yeast two-hybrid, co-immunoprecipitation, confocal microscopy, structure prediction, truncated/point mutant assays, PSMB4 overexpression/knockdown with viral protein level readouts","journal":"Cellular and molecular life sciences : CMLS","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — specific residues identified by mutagenesis with functional validation, multiple binding confirmation methods, single lab","pmids":["40192860"],"is_preprint":false}],"current_model":"PSMB4 (β7 subunit of the 20S proteasome) is an essential structural component for proteasome assembly whose activity is negatively regulated by direct interaction with presynaptic bassoon (via steric interference with 20S core assembly); it promotes cancer cell survival and tumor growth, drives NF-κB–miR-21 and NF-κB–IκBα signaling cascades across multiple cell types, is transcriptionally activated by FoxM1, facilitates invasion via pFAK/MMP9 and angiogenesis via VEGF-B, acts as an antiviral restriction factor by mediating K63-linked ubiquitination and lysosomal degradation of viral proteins (PRRSV Nsp1α, IAV NS1) through defined interaction domains (PSMB4 C-terminal aa 250–264; critical residues S146/M148), and interacts with the E3 ligase SNEV to couple ubiquitin-dependent substrate delivery to the proteasome."},"narrative":{"mechanistic_narrative":"PSMB4 is the β7 subunit of the 20S proteasome core and functions both as an essential structural component of the proteasome and as a node coupling ubiquitin-dependent protein turnover to cell survival, inflammatory signaling, and antiviral defense [PMID:15660529, PMID:32651614]. As a core subunit it is the docking site for substrate-delivery and regulatory factors: the E3 ubiquitin ligase SNEV/Prp19 binds PSMB4 directly and escorts ubiquitinated substrates to the proteasome, an interaction conserved between yeast and mammals [PMID:15660529], while the presynaptic scaffold bassoon binds PSMB4 through three interfaces and sterically interferes with 20S core assembly to attenuate all proteasomal endopeptidase activities, causing accumulation of proteasomal substrates [PMID:32651614]. PSMB4 was the first proteasomal subunit shown to have oncogenic properties, being required for cancer cell survival and tumor growth across many cell lines [PMID:24755469]. In tumor contexts it is transcriptionally driven by FoxM1 [PMID:31699366] and promotes proliferation, invasion, and angiogenesis through an NF-κB axis—activating NF-κB and upregulating miR-21 [PMID:25656574], degrading IκBα to sustain NF-κB activity [PMID:33954843], and elevating pFAK/MMP9, MLC, and VEGF-B/VEGFR2 to support migration and neovascularization [PMID:29414809, PMID:38791597]. PSMB4 also acts as an antiviral restriction factor: it binds and destabilizes influenza A virus NS1 [PMID:36298834] and PRRSV Nsp1α, mediating K63-linked ubiquitination of Nsp1α at K169 to route it for autolysosomal degradation via LC3 while activating NF-κB/type I interferon signaling, with binding mapped to the PSMB4 C-terminus (aa 250–264) and critical residues S146/M148 [PMID:36943051, PMID:40192860].","teleology":[{"year":2005,"claim":"Established that PSMB4 serves as a physical docking point linking ubiquitin-tagged substrate delivery to the proteasome core, answering how an E3 ligase couples to the 20S particle.","evidence":"Reciprocal Co-IP, yeast two-hybrid, and immunofluorescence with proteasome inhibition in mammalian and yeast systems","pmids":["15660529"],"confidence":"High","gaps":["No structural definition of the SNEV-PSMB4 interface","Whether this interaction modulates proteasome catalytic activity not addressed"]},{"year":2014,"claim":"Demonstrated that a core proteasomal subunit can itself be oncogenic, reframing PSMB4 from a passive structural part to a survival-promoting cancer dependency.","evidence":"RNAi loss-of-function across 32 cancer cell lines with in vivo xenograft validation","pmids":["24755469"],"confidence":"High","gaps":["Mechanism distinguishing PSMB4 dependency from general proteasome requirement unclear","No downstream effectors identified in this study"]},{"year":2015,"claim":"Placed PSMB4 upstream of an NF-κB–miR-21 proliferative axis and linked it to neuronal apoptosis, beginning to define the signaling consequences of its expression.","evidence":"Gain/loss-of-function with miR-21 rescue in myeloma cells; siRNA in primary neurons and LPS neuroinflammation model","pmids":["25656574","26282113"],"confidence":"Medium","gaps":["No biochemical mechanism for how PSMB4 activates NF-κB shown here","Single-lab observations"]},{"year":2016,"claim":"Extended PSMB4's regulatory reach to the RIP3/MLKL necroptosis pathway following spinal cord injury.","evidence":"Expression analysis, co-localization, and gain/loss-of-function in a TNF-α necroptosis cell model","pmids":["27514644"],"confidence":"Low","gaps":["Pathway placement based on co-localization and expression without direct biochemical interaction","Not independently confirmed"]},{"year":2018,"claim":"Identified pFAK and MMP9 as downstream effectors through which PSMB4 drives glioblastoma invasion, connecting it to an invasion/migration program.","evidence":"siRNA knockdown with proliferation, invasion, apoptosis assays and orthotopic xenograft","pmids":["29414809"],"confidence":"Medium","gaps":["Direct biochemical link between PSMB4 and FAK/MMP9 regulation not established","Single lab"]},{"year":2019,"claim":"Defined the upstream transcriptional control of PSMB4 by showing FoxM1 directly binds its promoter, establishing a FoxM1–PSMB4 axis driving proliferation.","evidence":"ChIP/promoter binding, siRNA, overexpression, rescue, and TCGA correlation in cervical cancer","pmids":["31699366"],"confidence":"Medium","gaps":["Whether FoxM1 regulation generalizes across cancer types not tested","Single lab"]},{"year":2020,"claim":"Revealed that PSMB4 is a regulatory target whose engagement controls proteasome activity, showing bassoon binds PSMB4 via three interfaces to sterically block 20S assembly and locally tune proteasomal degradation at synapses.","evidence":"Co-IP, deletion mapping, proteasome activity assays, bassoon KO mouse synaptic fractions, and rescue in primary neurons","pmids":["32651614"],"confidence":"High","gaps":["Atomic structure of the bassoon-PSMB4 interface not resolved","Whether other scaffolds use a similar mechanism unknown"]},{"year":2021,"claim":"Provided a direct molecular mechanism for PSMB4-driven NF-κB activation by showing it binds IκBα and promotes its proteasomal degradation, protecting cardiomyocytes from apoptosis.","evidence":"Co-IP, gain/loss-of-function in cardiomyocyte hypoxia/reoxygenation model with NF-κB and apoptosis readouts","pmids":["33954843"],"confidence":"Medium","gaps":["Whether IκBα is a direct catalytic substrate of the PSMB4-containing proteasome or recruited indirectly not resolved","Single lab"]},{"year":2022,"claim":"Established PSMB4 as an antiviral restriction factor by showing it binds influenza A NS1 and promotes its proteasome-dependent degradation to restore interferon responses.","evidence":"Yeast two-hybrid with domain mapping, Co-IP, confocal microscopy, MG132 protein-level assays, and IAV replication assays","pmids":["36298834"],"confidence":"Medium","gaps":["Ubiquitin-linkage type and degradation route for NS1 not defined","Single lab"]},{"year":2023,"claim":"Defined a complete antiviral mechanism in which PSMB4 mediates K63-linked ubiquitination of PRRSV Nsp1α at K169 for LC3-dependent autolysosomal degradation while activating NF-κB/IFN, with the interaction mapped to the PSMB4 C-terminus.","evidence":"Yeast two-hybrid, Co-IP, GST pulldown, confocal, K63 ubiquitination assays, autolysosome and NF-κB assays with PRRSV replication readouts","pmids":["36943051"],"confidence":"High","gaps":["How a 20S core subunit catalyzes K63-linked ubiquitination mechanistically unexplained","Whether PSMB4 acts as or recruits the E3 ligase unclear"]},{"year":2025,"claim":"Mapped the specific PSMB4 residues S146 and M148 required for binding and degrading PRRSV Nsp1α, refining the structural basis of antiviral recognition.","evidence":"Yeast two-hybrid, Co-IP, confocal, structure prediction, and truncated/point mutant assays with viral protein readouts","pmids":["40192860"],"confidence":"Medium","gaps":["Predicted rather than experimental structure","Single lab"]},{"year":null,"claim":"How PSMB4's structural role in the 20S core mechanistically gives rise to its substrate-selective, ubiquitin-linkage-specific, and signaling-regulatory activities remains unresolved.","evidence":"","pmids":[],"confidence":"Low","gaps":["No structural model of PSMB4 within an active proteasome bound to its regulatory partners","Unclear whether oncogenic and antiviral functions reflect proteasome-intrinsic activity or moonlighting interactions","Mechanism by which PSMB4 directs K63 ubiquitination toward the autolysosomal pathway undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[8,9,10]},{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,7]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[9,10]}],"localization":[{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,7]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,7,8]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[9,10]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,8]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[1,5]}],"complexes":["20S proteasome core"],"partners":["SNEV","PRPF19","BSN","IKBA","NS1","NSP1ALPHA","MAP1LC3"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P28070","full_name":"Proteasome subunit beta type-4","aliases":["26 kDa prosomal protein","HsBPROS26","PROS-26","Macropain beta chain","Multicatalytic endopeptidase complex beta chain","Proteasome beta chain","Proteasome chain 3","HsN3","Proteasome subunit beta-7","beta-7"],"length_aa":264,"mass_kda":29.2,"function":"Non-catalytic component of the 20S core proteasome complex involved in the proteolytic degradation of most intracellular proteins. This complex plays numerous essential roles within the cell by associating with different regulatory particles. Associated with two 19S regulatory particles, forms the 26S proteasome and thus participates in the ATP-dependent degradation of ubiquitinated proteins. The 26S proteasome plays a key role in the maintenance of protein homeostasis by removing misfolded or damaged proteins that could impair cellular functions, and by removing proteins whose functions are no longer required. Associated with the PA200 or PA28, the 20S proteasome mediates ubiquitin-independent protein degradation. This type of proteolysis is required in several pathways including spermatogenesis (20S-PA200 complex) or generation of a subset of MHC class I-presented antigenic peptides (20S-PA28 complex). SMAD1/OAZ1/PSMB4 complex mediates the degradation of the CREBBP/EP300 repressor SNIP1","subcellular_location":"Cytoplasm; Nucleus","url":"https://www.uniprot.org/uniprotkb/P28070/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/PSMB4","classification":"Common Essential","n_dependent_lines":1208,"n_total_lines":1208,"dependency_fraction":1.0},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000159377","cell_line_id":"CID000097","localizations":[{"compartment":"nucleoplasm","grade":3},{"compartment":"cytoplasmic","grade":2}],"interactors":[{"gene":"PSMD12","stoichiometry":10.0},{"gene":"PSMD11","stoichiometry":10.0},{"gene":"PSMD3","stoichiometry":10.0},{"gene":"PSMA7","stoichiometry":10.0},{"gene":"PSMC2","stoichiometry":10.0},{"gene":"PSMA5","stoichiometry":10.0},{"gene":"PSMB2","stoichiometry":10.0},{"gene":"PSMC4","stoichiometry":10.0},{"gene":"PSMB1","stoichiometry":10.0},{"gene":"PSMA2","stoichiometry":10.0}],"url":"https://opencell.sf.czbiohub.org/target/CID000097","total_profiled":1310},"omim":[{"mim_id":"617591","title":"PROTEASOME-ASSOCIATED AUTOINFLAMMATORY SYNDROME 3; PRAAS3","url":"https://www.omim.org/entry/617591"},{"mim_id":"613787","title":"MICRO RNA 148B; MIR148B","url":"https://www.omim.org/entry/613787"},{"mim_id":"602177","title":"PROTEASOME SUBUNIT, BETA-TYPE, 4; PSMB4","url":"https://www.omim.org/entry/602177"},{"mim_id":"602175","title":"PROTEASOME SUBUNIT, BETA-TYPE, 2; PSMB2","url":"https://www.omim.org/entry/602175"},{"mim_id":"601148","title":"SPERM MITOCHONDRIA-ASSOCIATED CYSTEINE-RICH PROTEIN; SMCP","url":"https://www.omim.org/entry/601148"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Nucleoplasm","reliability":"Supported"},{"location":"Mitochondria","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/PSMB4"},"hgnc":{"alias_symbol":["HN3","PROS26"],"prev_symbol":[]},"alphafold":{"accession":"P28070","domains":[{"cath_id":"3.60.20.10","chopping":"50-246","consensus_level":"medium","plddt":97.2048,"start":50,"end":246}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P28070","model_url":"https://alphafold.ebi.ac.uk/files/AF-P28070-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P28070-F1-predicted_aligned_error_v6.png","plddt_mean":87.44},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PSMB4","jax_strain_url":"https://www.jax.org/strain/search?query=PSMB4"},"sequence":{"accession":"P28070","fasta_url":"https://rest.uniprot.org/uniprotkb/P28070.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P28070/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P28070"}},"corpus_meta":[{"pmid":"24755469","id":"PMC_24755469","title":"Comparative oncogenomics identifies PSMB4 and SHMT2 as potential cancer driver genes.","date":"2014","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/24755469","citation_count":137,"is_preprint":false},{"pmid":"18805649","id":"PMC_18805649","title":"Comparison of toxicity associated with early morning versus late afternoon radiotherapy in patients with head-and-neck cancer: a prospective randomized trial of the National Cancer Institute of Canada Clinical Trials Group (HN3).","date":"2008","source":"International journal of radiation oncology, biology, physics","url":"https://pubmed.ncbi.nlm.nih.gov/18805649","citation_count":89,"is_preprint":false},{"pmid":"31520528","id":"PMC_31520528","title":"Engineered Anti-GPC3 Immunotoxin, HN3-ABD-T20, Produces Regression in Mouse Liver Cancer Xenografts Through Prolonged Serum Retention.","date":"2020","source":"Hepatology (Baltimore, Md.)","url":"https://pubmed.ncbi.nlm.nih.gov/31520528","citation_count":54,"is_preprint":false},{"pmid":"23064512","id":"PMC_23064512","title":"Combination treatment with photodynamic therapy and curcumin induces mitochondria-dependent apoptosis in AMC-HN3 cells.","date":"2012","source":"International journal of oncology","url":"https://pubmed.ncbi.nlm.nih.gov/23064512","citation_count":53,"is_preprint":false},{"pmid":"15660529","id":"PMC_15660529","title":"Interaction of U-box E3 ligase SNEV with PSMB4, the beta7 subunit of the 20 S proteasome.","date":"2005","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/15660529","citation_count":52,"is_preprint":false},{"pmid":"27419635","id":"PMC_27419635","title":"Construction of an immunotoxin, HN3-mPE24, targeting glypican-3 for liver cancer therapy.","date":"2017","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/27419635","citation_count":42,"is_preprint":false},{"pmid":"25656574","id":"PMC_25656574","title":"PSMB4 promotes multiple myeloma cell growth by activating NF-κB-miR-21 signaling.","date":"2015","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/25656574","citation_count":29,"is_preprint":false},{"pmid":"32651614","id":"PMC_32651614","title":"Bassoon inhibits proteasome activity via interaction with PSMB4.","date":"2020","source":"Cellular and molecular life sciences : CMLS","url":"https://pubmed.ncbi.nlm.nih.gov/32651614","citation_count":27,"is_preprint":false},{"pmid":"30546448","id":"PMC_30546448","title":"Oxidative stress induced by carboplatin promotes apoptosis and inhibits migration of HN-3 cells.","date":"2018","source":"Oncology 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activities in Elaeagnus angustifolia var. orientalis (L.)Kuntze fruit juice enhanced by Bifidobacterium animalis subsp. Lactis HN-3 fermentation.","date":"2021","source":"Food chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/34815112","citation_count":16,"is_preprint":false},{"pmid":"33954843","id":"PMC_33954843","title":"PSMB4 inhibits cardiomyocyte apoptosis via activating NF-κB signaling pathway during myocardial ischemia/reperfusion injury.","date":"2021","source":"Journal of molecular histology","url":"https://pubmed.ncbi.nlm.nih.gov/33954843","citation_count":14,"is_preprint":false},{"pmid":"16410550","id":"PMC_16410550","title":"A molecular link A molecular link between Hairless and Pros26.4, a member of the AAA-ATPase subunits of the proteasome 19S regulatory particle in Drosophila.","date":"2006","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/16410550","citation_count":14,"is_preprint":false},{"pmid":"28821255","id":"PMC_28821255","title":"The whole genomic analysis of orf virus strain HN3/12 isolated from Henan province, central China.","date":"2017","source":"BMC veterinary research","url":"https://pubmed.ncbi.nlm.nih.gov/28821255","citation_count":14,"is_preprint":false},{"pmid":"27514644","id":"PMC_27514644","title":"Upregulation of PSMB4 is Associated with the Necroptosis after Spinal Cord Injury.","date":"2016","source":"Neurochemical research","url":"https://pubmed.ncbi.nlm.nih.gov/27514644","citation_count":12,"is_preprint":false},{"pmid":"30272304","id":"PMC_30272304","title":"Mechanism of HN‑3 cell apoptosis induced by carboplatin: Combination of mitochondrial pathway associated with Ca2+ and the nucleus pathways.","date":"2018","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/30272304","citation_count":12,"is_preprint":false},{"pmid":"33062407","id":"PMC_33062407","title":"Engineering of HN3 increases the tumor targeting specificity of exosomes and upgrade the anti-tumor effect of sorafenib on HuH-7 cells.","date":"2020","source":"PeerJ","url":"https://pubmed.ncbi.nlm.nih.gov/33062407","citation_count":11,"is_preprint":false},{"pmid":"29414809","id":"PMC_29414809","title":"Interference with PSMB4 Expression Exerts an Anti-Tumor Effect by Decreasing the Invasion and Proliferation of Human Glioblastoma Cells.","date":"2018","source":"Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/29414809","citation_count":10,"is_preprint":false},{"pmid":"26282113","id":"PMC_26282113","title":"Up-regulation of PSMB4 is associated with neuronal apoptosis after neuroinflammation induced by lipopolysaccharide.","date":"2015","source":"Journal of molecular histology","url":"https://pubmed.ncbi.nlm.nih.gov/26282113","citation_count":10,"is_preprint":false},{"pmid":"31699366","id":"PMC_31699366","title":"A novel FoxM1-PSMB4 axis contributes to proliferation and progression of cervical cancer.","date":"2019","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/31699366","citation_count":8,"is_preprint":false},{"pmid":"24946957","id":"PMC_24946957","title":"Predictive value of PAK6 and PSMB4 expression in patients with localized prostate cancer treated with dose-escalation radiation therapy and androgen deprivation therapy.","date":"2014","source":"Urologic oncology","url":"https://pubmed.ncbi.nlm.nih.gov/24946957","citation_count":8,"is_preprint":false},{"pmid":"36298834","id":"PMC_36298834","title":"Cellular PSMB4 Protein Suppresses Influenza A Virus Replication through Targeting NS1 Protein.","date":"2022","source":"Viruses","url":"https://pubmed.ncbi.nlm.nih.gov/36298834","citation_count":7,"is_preprint":false},{"pmid":"23846258","id":"PMC_23846258","title":"The apoptosis pathway of photodynamic therapy using 9-HpbD-a in AMC-HN3 human head and neck cancer cell line and in vivo.","date":"2013","source":"General physiology and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/23846258","citation_count":6,"is_preprint":false},{"pmid":"890145","id":"PMC_890145","title":"Hematologic and immunologic studies in dogs given nitrogen mustard (hn3).","date":"1977","source":"Blut","url":"https://pubmed.ncbi.nlm.nih.gov/890145","citation_count":6,"is_preprint":false},{"pmid":"35070625","id":"PMC_35070625","title":"Analysis of the complete genome sequence of a rhizosphere-derived Pseudomonas sp. HN3-2 leads to the characterization of a cyclic lipopeptide-type antibiotic bananamide C.","date":"2022","source":"3 Biotech","url":"https://pubmed.ncbi.nlm.nih.gov/35070625","citation_count":4,"is_preprint":false},{"pmid":"40560191","id":"PMC_40560191","title":"Comprehensive reexamination of the acute toxicity of nitrogen mustards: HN-1, HN-2 and HN-3 as blister agents: application of multi in silico approach.","date":"2025","source":"Archives of toxicology","url":"https://pubmed.ncbi.nlm.nih.gov/40560191","citation_count":4,"is_preprint":false},{"pmid":"40192860","id":"PMC_40192860","title":"S146 and M148 within the mature chain domain of PSMB4 are crucial for degrading PRRSV nsp1α.","date":"2025","source":"Cellular and molecular life sciences : CMLS","url":"https://pubmed.ncbi.nlm.nih.gov/40192860","citation_count":3,"is_preprint":false},{"pmid":"38791597","id":"PMC_38791597","title":"The Reduction of PSMB4 in T24 and J82 Bladder Cancer Cells Inhibits the Angiogenesis and Migration of Endothelial Cells.","date":"2024","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/38791597","citation_count":3,"is_preprint":false},{"pmid":"39979251","id":"PMC_39979251","title":"PSMB4: a potential biomarker and therapeutic target for depression, perspective from integration analysis of depression GWAS data and human plasma proteome.","date":"2025","source":"Translational psychiatry","url":"https://pubmed.ncbi.nlm.nih.gov/39979251","citation_count":2,"is_preprint":false},{"pmid":"19916540","id":"PMC_19916540","title":"Thermal decomposition of HN(3).","date":"2010","source":"The journal of physical chemistry. A","url":"https://pubmed.ncbi.nlm.nih.gov/19916540","citation_count":1,"is_preprint":false},{"pmid":"26685405","id":"PMC_26685405","title":"[Apoptosis and migration suppression of HN-3 human laryngeal squamous cancer cells induced by photo-activation of 9-hydroxypheophorbide-α].","date":"2015","source":"Lin chuang er bi yan hou tou jing wai ke za zhi = Journal of clinical otorhinolaryngology head and neck surgery","url":"https://pubmed.ncbi.nlm.nih.gov/26685405","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.11.21.689729","title":"Effects of a novel proteasome inhibitor, UR238 on the tumor immune microenvironment and growth in epithelial ovarian cancer","date":"2025-11-24","source":"bioRxiv","url":"https://doi.org/10.1101/2025.11.21.689729","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":18860,"output_tokens":3831,"usd":0.057022,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":11681,"output_tokens":3819,"usd":0.07694,"stage2_stop_reason":"end_turn"},"total_usd":0.133962,"stage1_batch_id":"msgbatch_01CNoDbkChHEkgrJnL7BwtGJ","stage2_batch_id":"msgbatch_016Y4x9E9Wg5VQDANj9quSQD","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2005,\n      \"finding\": \"The E3 ubiquitin ligase SNEV (senescence evasion factor) directly binds to PSMB4, the β7 subunit of the 20S proteasome, physically linking the ubiquitin-proteasome system to the spliceosome. Upon proteasome inhibition, SNEV co-localization with PSMB4 increases, and SNEV co-localizes with ubiquitin without itself being ubiquitinated, suggesting SNEV escorts substrates to the proteasome via this interaction. The yeast homologue of SNEV (Prp19) also interacts with the yeast β7 subunit, indicating evolutionary conservation.\",\n      \"method\": \"Co-immunoprecipitation, yeast two-hybrid, immunofluorescence microscopy, proteasome inhibition experiments\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, yeast two-hybrid, immunofluorescence with proteasome inhibitor, replicated across yeast and mammalian systems in one study with multiple orthogonal methods\",\n      \"pmids\": [\"15660529\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"PSMB4 was identified as the first proteasomal subunit with oncogenic properties: RNAi-mediated loss-of-function reduced cancer cell survival across a panel of 32 cancer cell lines, and functional assays demonstrated PSMB4 is necessary for tumor cell survival and tumor growth in vivo.\",\n      \"method\": \"RNAi loss-of-function screen across 32 cancer cell lines, in vivo xenograft tumor growth assays\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — large-scale RNAi screen followed by in vivo validation, multiple cell lines and orthogonal readouts\",\n      \"pmids\": [\"24755469\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PSMB4 overexpression in multiple myeloma cells activates NF-κB signaling and upregulates miR-21, promoting cell growth and colony formation. PSMB4 knockdown suppresses NF-κB activity and miR-21 expression. Re-expression of miR-21 rescues the growth suppression caused by PSMB4 knockdown, placing PSMB4 upstream of NF-κB–miR-21 in a proliferative signaling axis.\",\n      \"method\": \"Ectopic overexpression and siRNA knockdown, NF-κB reporter assays, miRNA expression analysis, rescue experiments with miR-21 re-expression\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss- and gain-of-function with rescue experiment in a single lab, multiple readouts but no structural or in vitro biochemical confirmation of direct NF-κB activation mechanism\",\n      \"pmids\": [\"25656574\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"PSMB4 knockdown by siRNA in a neuroinflammation model reduces the upregulation of active caspase-3, cyclin D1, and CDK4 in cortical primary neurons, indicating PSMB4 contributes to neuronal apoptosis downstream of LPS-induced neuroinflammation via these apoptosis- and cell-cycle-related proteins.\",\n      \"method\": \"siRNA knockdown in primary neurons and rat LPS neuroinflammation model, western blotting, immunohistochemistry\",\n      \"journal\": \"Journal of molecular histology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — loss-of-function with specific molecular readouts in a single lab, single method set\",\n      \"pmids\": [\"26282113\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"PSMB4 expression is upregulated in neurons after spinal cord injury, co-localizing with RIP3-positive neurons. Overexpression and knockdown of PSMB4 modulates RIP3 and MLKL levels in a TNF-α-induced necroptosis cell model, implicating PSMB4 in regulation of the RIP3/MLKL necroptosis pathway.\",\n      \"method\": \"Western blot, immunohistochemistry, immunofluorescence staining, PSMB4 overexpression and knockdown in necroptosis cell model\",\n      \"journal\": \"Neurochemical research\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — single lab, indirect pathway placement based on co-localization and expression changes without direct biochemical interaction data\",\n      \"pmids\": [\"27514644\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"PSMB4 knockdown in glioblastoma cells decreases proliferation, migration, and invasion, induces cell cycle arrest and apoptosis, and reduces expression of phosphorylated focal adhesion kinase (pFAK) and matrix metallopeptidase 9 (MMP9) in vivo, identifying these as downstream effectors of PSMB4-driven invasion.\",\n      \"method\": \"siRNA knockdown, MTT assay, Annexin V/PI flow cytometry, wound healing and Transwell invasion assays, western blotting, orthotopic xenograft mouse model\",\n      \"journal\": \"Cellular physiology and biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function confirmed in vitro and in vivo with multiple orthogonal functional readouts in a single lab\",\n      \"pmids\": [\"29414809\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"FoxM1, a master regulator of cell division, directly binds to the promoter region of PSMB4 and transcriptionally activates PSMB4 expression. Loss-of-function and rescue experiments confirm PSMB4 is required downstream of FoxM1 to drive cervical cancer cell proliferation, establishing a FoxM1–PSMB4 transcriptional axis.\",\n      \"method\": \"ChIP/promoter binding assay, siRNA knockdown, overexpression, rescue experiments, TCGA correlation analysis\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct promoter binding demonstrated, loss-of-function with rescue in single lab, multiple orthogonal methods\",\n      \"pmids\": [\"31699366\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Bassoon (Bsn), a presynaptic scaffolding protein, directly interacts with PSMB4 (β7 subunit of 20S core proteasome) via three independent interaction interfaces. Expression of PSMB4-interacting fragments of bassoon in cell lines or primary neurons attenuates all endopeptidase activities of cellular proteasome and induces accumulation of ubiquitinated and non-ubiquitinated proteasomal substrates, likely through steric interference with 20S core assembly. Bassoon knockout mice show increased proteasomal activity and depletion of synaptic proteasomal substrates, which is reversed by expressing PSMB4-interacting bassoon fragments.\",\n      \"method\": \"Co-immunoprecipitation, deletion mapping of interaction interfaces, proteasome activity assays, bassoon knockout mouse brains (synaptic fractionation), primary neuron expression experiments, substrate accumulation assays\",\n      \"journal\": \"Cellular and molecular life sciences : CMLS\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — direct interaction mapped to three interfaces, in-cell proteasome activity assays, genetic KO rescue with mechanistic specificity, multiple orthogonal methods in one rigorous study\",\n      \"pmids\": [\"32651614\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"PSMB4 directly interacts with IκBα and promotes its proteasome-dependent degradation, thereby activating NF-κB signaling and inhibiting cardiomyocyte apoptosis during hypoxia/reoxygenation injury. PSMB4 silence increases IκBα levels and suppresses NF-κB activation, while PSMB4 overexpression has opposite effects.\",\n      \"method\": \"Co-immunoprecipitation (PSMB4–IκBα interaction), siRNA knockdown and overexpression in neonatal cardiomyocyte H/R model, NF-κB activation assays, western blotting for IκBα and apoptosis markers\",\n      \"journal\": \"Journal of molecular histology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP identifies IκBα as binding partner, gain- and loss-of-function with mechanistic readouts, single lab\",\n      \"pmids\": [\"33954843\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"PSMB4 physically interacts with influenza A virus NS1 protein (interaction mapped by yeast two-hybrid and confirmed by Co-IP and confocal microscopy in mammalian cells). PSMB4 reduces NS1 protein levels, especially in the presence of proteasome inhibitor MG132, and suppresses NS1 functions including interferon inhibition and transient gene expression enhancement. PSMB4 knockdown enhances IAV replication while overexpression attenuates it.\",\n      \"method\": \"Yeast two-hybrid screening (binding domain mapping), co-immunoprecipitation, confocal microscopy, NS1 protein level assays with MG132, IAV replication assays with knockdown/overexpression\",\n      \"journal\": \"Viruses\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — interaction confirmed by two orthogonal methods with domain mapping, functional consequence on viral replication shown by gain- and loss-of-function, single lab\",\n      \"pmids\": [\"36298834\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PSMB4 interacts with PRRSV Nsp1α protein; the PCPα domain (aa 66–166) of Nsp1α and the C-terminal domain (aa 250–264) of PSMB4 are critical for this interaction. PSMB4 mediates K63-linked ubiquitination of Nsp1α at K169, targeting Nsp1α for autolysosomal degradation by interacting with LC3 to enhance lysosomal pathway activation. PSMB4 also activates NF-κB signaling to induce type I interferon production by downregulating IκBα and p-IκBα expression, thereby restricting PRRSV replication.\",\n      \"method\": \"Yeast two-hybrid screening, co-immunoprecipitation, GST pulldown, laser confocal microscopy, ubiquitination assays (K63-linkage), autolysosome pathway assays, NF-κB signaling assays, PSMB4 overexpression and knockdown with PRRSV replication readouts\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Strong — interaction confirmed by three orthogonal methods, domain mapping, specific ubiquitination site identified (K169), mechanistic pathway (autolysosome + NF-κB/IFN) established with multiple functional assays in one study\",\n      \"pmids\": [\"36943051\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PSMB4 knockdown in bladder cancer cells reduces expression of phosphorylated FAK and myosin light chain (MLC), leading to decreased cancer cell migration. PSMB4 suppression also decreases VEGF-B levels, reducing angiogenic capacity and lowering VEGFR2 expression in HUVECs. In vivo metastatic models show PSMB4 knockdown reduces lung tumor volumes.\",\n      \"method\": \"siRNA knockdown, western blotting (pFAK, MLC, VEGF-B, VEGFR2), migration/angiogenesis assays, in vivo metastatic mouse model\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — loss-of-function with specific downstream molecular targets identified, in vitro and in vivo validation, single lab\",\n      \"pmids\": [\"38791597\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"S146 and M148 within the mature chain domain of PSMB4 are critical residues for binding and degrading PRRSV nsp1α. Truncated mutant assays and structure prediction showed these residues mediate the PSMB4–nsp1α interaction, and PSMB4 overexpression reduces nsp1α and viral N protein levels in a dose-dependent manner while knockdown promotes PRRSV replication.\",\n      \"method\": \"Yeast two-hybrid, co-immunoprecipitation, confocal microscopy, structure prediction, truncated/point mutant assays, PSMB4 overexpression/knockdown with viral protein level readouts\",\n      \"journal\": \"Cellular and molecular life sciences : CMLS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — specific residues identified by mutagenesis with functional validation, multiple binding confirmation methods, single lab\",\n      \"pmids\": [\"40192860\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PSMB4 (β7 subunit of the 20S proteasome) is an essential structural component for proteasome assembly whose activity is negatively regulated by direct interaction with presynaptic bassoon (via steric interference with 20S core assembly); it promotes cancer cell survival and tumor growth, drives NF-κB–miR-21 and NF-κB–IκBα signaling cascades across multiple cell types, is transcriptionally activated by FoxM1, facilitates invasion via pFAK/MMP9 and angiogenesis via VEGF-B, acts as an antiviral restriction factor by mediating K63-linked ubiquitination and lysosomal degradation of viral proteins (PRRSV Nsp1α, IAV NS1) through defined interaction domains (PSMB4 C-terminal aa 250–264; critical residues S146/M148), and interacts with the E3 ligase SNEV to couple ubiquitin-dependent substrate delivery to the proteasome.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PSMB4 is the β7 subunit of the 20S proteasome core and functions both as an essential structural component of the proteasome and as a node coupling ubiquitin-dependent protein turnover to cell survival, inflammatory signaling, and antiviral defense [#0, #7]. As a core subunit it is the docking site for substrate-delivery and regulatory factors: the E3 ubiquitin ligase SNEV/Prp19 binds PSMB4 directly and escorts ubiquitinated substrates to the proteasome, an interaction conserved between yeast and mammals [#0], while the presynaptic scaffold bassoon binds PSMB4 through three interfaces and sterically interferes with 20S core assembly to attenuate all proteasomal endopeptidase activities, causing accumulation of proteasomal substrates [#7]. PSMB4 was the first proteasomal subunit shown to have oncogenic properties, being required for cancer cell survival and tumor growth across many cell lines [#1]. In tumor contexts it is transcriptionally driven by FoxM1 [#6] and promotes proliferation, invasion, and angiogenesis through an NF-κB axis—activating NF-κB and upregulating miR-21 [#2], degrading IκBα to sustain NF-κB activity [#8], and elevating pFAK/MMP9, MLC, and VEGF-B/VEGFR2 to support migration and neovascularization [#5, #11]. PSMB4 also acts as an antiviral restriction factor: it binds and destabilizes influenza A virus NS1 [#9] and PRRSV Nsp1α, mediating K63-linked ubiquitination of Nsp1α at K169 to route it for autolysosomal degradation via LC3 while activating NF-κB/type I interferon signaling, with binding mapped to the PSMB4 C-terminus (aa 250–264) and critical residues S146/M148 [#10, #12].\",\n  \"teleology\": [\n    {\n      \"year\": 2005,\n      \"claim\": \"Established that PSMB4 serves as a physical docking point linking ubiquitin-tagged substrate delivery to the proteasome core, answering how an E3 ligase couples to the 20S particle.\",\n      \"evidence\": \"Reciprocal Co-IP, yeast two-hybrid, and immunofluorescence with proteasome inhibition in mammalian and yeast systems\",\n      \"pmids\": [\"15660529\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural definition of the SNEV-PSMB4 interface\", \"Whether this interaction modulates proteasome catalytic activity not addressed\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Demonstrated that a core proteasomal subunit can itself be oncogenic, reframing PSMB4 from a passive structural part to a survival-promoting cancer dependency.\",\n      \"evidence\": \"RNAi loss-of-function across 32 cancer cell lines with in vivo xenograft validation\",\n      \"pmids\": [\"24755469\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism distinguishing PSMB4 dependency from general proteasome requirement unclear\", \"No downstream effectors identified in this study\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Placed PSMB4 upstream of an NF-κB–miR-21 proliferative axis and linked it to neuronal apoptosis, beginning to define the signaling consequences of its expression.\",\n      \"evidence\": \"Gain/loss-of-function with miR-21 rescue in myeloma cells; siRNA in primary neurons and LPS neuroinflammation model\",\n      \"pmids\": [\"25656574\", \"26282113\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No biochemical mechanism for how PSMB4 activates NF-κB shown here\", \"Single-lab observations\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Extended PSMB4's regulatory reach to the RIP3/MLKL necroptosis pathway following spinal cord injury.\",\n      \"evidence\": \"Expression analysis, co-localization, and gain/loss-of-function in a TNF-α necroptosis cell model\",\n      \"pmids\": [\"27514644\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Pathway placement based on co-localization and expression without direct biochemical interaction\", \"Not independently confirmed\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identified pFAK and MMP9 as downstream effectors through which PSMB4 drives glioblastoma invasion, connecting it to an invasion/migration program.\",\n      \"evidence\": \"siRNA knockdown with proliferation, invasion, apoptosis assays and orthotopic xenograft\",\n      \"pmids\": [\"29414809\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct biochemical link between PSMB4 and FAK/MMP9 regulation not established\", \"Single lab\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Defined the upstream transcriptional control of PSMB4 by showing FoxM1 directly binds its promoter, establishing a FoxM1–PSMB4 axis driving proliferation.\",\n      \"evidence\": \"ChIP/promoter binding, siRNA, overexpression, rescue, and TCGA correlation in cervical cancer\",\n      \"pmids\": [\"31699366\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether FoxM1 regulation generalizes across cancer types not tested\", \"Single lab\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Revealed that PSMB4 is a regulatory target whose engagement controls proteasome activity, showing bassoon binds PSMB4 via three interfaces to sterically block 20S assembly and locally tune proteasomal degradation at synapses.\",\n      \"evidence\": \"Co-IP, deletion mapping, proteasome activity assays, bassoon KO mouse synaptic fractions, and rescue in primary neurons\",\n      \"pmids\": [\"32651614\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic structure of the bassoon-PSMB4 interface not resolved\", \"Whether other scaffolds use a similar mechanism unknown\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Provided a direct molecular mechanism for PSMB4-driven NF-κB activation by showing it binds IκBα and promotes its proteasomal degradation, protecting cardiomyocytes from apoptosis.\",\n      \"evidence\": \"Co-IP, gain/loss-of-function in cardiomyocyte hypoxia/reoxygenation model with NF-κB and apoptosis readouts\",\n      \"pmids\": [\"33954843\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether IκBα is a direct catalytic substrate of the PSMB4-containing proteasome or recruited indirectly not resolved\", \"Single lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Established PSMB4 as an antiviral restriction factor by showing it binds influenza A NS1 and promotes its proteasome-dependent degradation to restore interferon responses.\",\n      \"evidence\": \"Yeast two-hybrid with domain mapping, Co-IP, confocal microscopy, MG132 protein-level assays, and IAV replication assays\",\n      \"pmids\": [\"36298834\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Ubiquitin-linkage type and degradation route for NS1 not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined a complete antiviral mechanism in which PSMB4 mediates K63-linked ubiquitination of PRRSV Nsp1α at K169 for LC3-dependent autolysosomal degradation while activating NF-κB/IFN, with the interaction mapped to the PSMB4 C-terminus.\",\n      \"evidence\": \"Yeast two-hybrid, Co-IP, GST pulldown, confocal, K63 ubiquitination assays, autolysosome and NF-κB assays with PRRSV replication readouts\",\n      \"pmids\": [\"36943051\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How a 20S core subunit catalyzes K63-linked ubiquitination mechanistically unexplained\", \"Whether PSMB4 acts as or recruits the E3 ligase unclear\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Mapped the specific PSMB4 residues S146 and M148 required for binding and degrading PRRSV Nsp1α, refining the structural basis of antiviral recognition.\",\n      \"evidence\": \"Yeast two-hybrid, Co-IP, confocal, structure prediction, and truncated/point mutant assays with viral protein readouts\",\n      \"pmids\": [\"40192860\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Predicted rather than experimental structure\", \"Single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How PSMB4's structural role in the 20S core mechanistically gives rise to its substrate-selective, ubiquitin-linkage-specific, and signaling-regulatory activities remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No structural model of PSMB4 within an active proteasome bound to its regulatory partners\", \"Unclear whether oncogenic and antiviral functions reflect proteasome-intrinsic activity or moonlighting interactions\", \"Mechanism by which PSMB4 directs K63 ubiquitination toward the autolysosomal pathway undefined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [8, 9, 10]},\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 7]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [9, 10]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 7, 8]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [9, 10]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 8]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [1, 5]}\n    ],\n    \"complexes\": [\n      \"20S proteasome core\"\n    ],\n    \"partners\": [\n      \"SNEV\",\n      \"PRPF19\",\n      \"BSN\",\n      \"IKBA\",\n      \"NS1\",\n      \"Nsp1alpha\",\n      \"MAP1LC3\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":4,"faith_total":5,"faith_pct":80.0}}