Affinage

PSMB3

Proteasome subunit beta type-3 · UniProt P49720

Round 2 corrected
Length
205 aa
Mass
22.9 kDa
Annotated
2026-04-28
57 papers in source corpus 11 papers cited in narrative 11 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

PSMB3 encodes the beta-3 subunit of the 20S proteasome core particle, which assembles with other alpha and beta subunits to form the multicatalytic threonine protease complex that, together with the 19S regulatory particle, constitutes the 26S proteasome responsible for ubiquitin-dependent protein degradation (PMID:8811196, PMID:10436176). Beyond its general housekeeping role in proteostasis, PSMB3-dependent proteasome activity is specifically required for FANCD2 monoubiquitination in the Fanconi anemia DNA damage response (PMID:17671210), for CTG·CAG trinucleotide repeat expansion in human cells (PMID:23620289), and for restricting adeno-associated virus trafficking through the secretory pathway (PMID:21625534). Basal PSMB3 transcription in cancer cells is maintained by an NFE2L1/NFE2L3–CPEB3 regulatory axis, and its depletion impairs overall proteasome capacity, sensitizing myeloma cells to bortezomib and triggering compensatory transcriptional responses such as TRIB1 induction in hepatocytes (PMID:32366381, PMID:21289309, PMID:37291259). The human PSMB3 locus maps to chromosome 2q35, independently of the MHC-linked inducible proteasome subunit genes (PMID:9344661).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 1996 High

    Establishing that PSMB3 is an integral beta-type subunit of the 20S proteasome core resolved its identity as part of the threonine-based multicatalytic protease that forms the catalytic heart of the 26S proteasome.

    Evidence Biochemical purification, structural analysis, and protease activity assays of 20S and 26S proteasome complexes

    PMID:8811196

    Open questions at the time
    • Precise catalytic contribution of beta-3 versus other beta subunits not resolved
    • No structure of PSMB3 alone or its specific active site
  2. 1997 High

    Mapping PSMB3 to human chromosome 2q35 established that constitutive proteasome subunit genes are genomically dispersed from MHC-linked inducible subunits, implying distinct transcriptional regulation.

    Evidence FISH of genomic clones to human metaphase chromosomes

    PMID:9344661

    Open questions at the time
    • Cis-regulatory elements controlling PSMB3 transcription were not identified
    • Relationship between genomic location and tissue-specific expression unexplored
  3. 1999 High

    Cloning and biochemical verification of the mouse PSMB3 ortholog confirmed cross-species conservation and validated it as one of the 17 subunits of the mammalian 20S core.

    Evidence cDNA cloning, 2D-NEPHGE-PAGE, and immunoblotting with subunit-specific antisera in mouse

    PMID:10436176

    Open questions at the time
    • Functional equivalence between mouse and human PSMB3 assumed but not tested by complementation
  4. 2007 Medium

    Demonstrating that PSMB3 knockdown blocks FANCD2 monoubiquitination revealed a specific requirement for proteasome activity in activating the Fanconi anemia DNA damage pathway, moving PSMB3 biology beyond generic proteostasis.

    Evidence siRNA knockdown in human cells with FANCD2 ubiquitination and foci formation assays

    PMID:17671210

    Open questions at the time
    • Whether the effect is direct or reflects general proteostasis collapse is unclear
    • The proteasome substrate whose degradation activates FANCD2 was not identified
    • Single-lab finding
  5. 2011 Medium

    Three independent functional genomic studies linked PSMB3 to diverse biological contexts — AAV restriction at the secretory pathway, bortezomib sensitivity in myeloma, and potential thymic peptide generation — broadening the phenotypic landscape of PSMB3 loss.

    Evidence siRNA knockdown with AAV transduction assays in airway epithelium; genome-wide siRNA screen measuring bortezomib synergy in myeloma; microarray profiling of thymic epithelial cells

    PMID:21289309 PMID:21625534 PMID:21773946

    Open questions at the time
    • AAV restriction mechanism (ER/Golgi trafficking versus capsid degradation) not resolved
    • Bortezomib synergy screen did not dissect PSMB3-specific mechanism from general proteasome impairment
    • Thymic expression data lack functional validation for T cell selection
  6. 2013 Medium

    Showing that PSMB3 depletion reduces CTG·CAG trinucleotide repeat expansions established that proteasome proteolytic activity — not merely a stress response — drives microsatellite instability in human cells.

    Evidence siRNA knockdown in human astrocytic cells with quantitative repeat expansion assay; proteasome inhibitor controls discriminated proteolytic from stress-response mechanisms

    PMID:23620289

    Open questions at the time
    • Identity of the proteasome substrate whose turnover promotes repeat expansion is unknown
    • Generalizability to other repeat types not tested
    • Single-lab result
  7. 2020 Medium

    Identification of the NFE2L1/NFE2L3–CPEB3 axis as a regulator of basal PSMB3 expression in cancer cells revealed how proteasome subunit transcription is maintained under non-stress conditions, complementing the known stress-induced bounce-back pathway.

    Evidence Double siRNA knockdown of NFE2L1/NFE2L3, qRT-PCR, proteasome activity assays, and polysome profiling in cancer cell lines

    PMID:32366381

    Open questions at the time
    • PSMB3 was one of seven coordinately regulated subunits; unique regulatory elements of PSMB3 not dissected
    • Whether the axis operates in non-transformed cells is unknown
  8. 2023 Medium

    Demonstrating that PSMB3 silencing in hepatocytes induces TRIB1 transcription provided the first link between proteasome capacity and the TRIB1 regulatory network, suggesting a feedback loop connecting proteostasis and lipid/metabolic gene regulation.

    Evidence siRNA knockdown of PSMB3 in HuH-7 and HepG2 cells with RT-qPCR for TRIB1 and western blot for ubiquitylation

    PMID:37291259

    Open questions at the time
    • Mechanism connecting proteasome inhibition to TRIB1 transcription not identified
    • Whether TRIB1 induction is specific to PSMB3 loss or a generic proteasome impairment response is unclear
    • In vivo relevance not established

Open questions

Synthesis pass · forward-looking unresolved questions
  • The specific catalytic or structural contribution of the beta-3 subunit to 20S proteasome activity — as distinct from other constitutive beta subunits — remains undefined, and no disease-causing mutations in PSMB3 have been reported.
  • No active-site mutagenesis distinguishing PSMB3's catalytic role from assembly function
  • No loss-of-function animal model
  • No Mendelian disease association established

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005198 structural molecule activity 2 GO:0016787 hydrolase activity 2 GO:0140096 catalytic activity, acting on a protein 2
Localization
GO:0005829 cytosol 2 GO:0005634 nucleus 1
Pathway
R-HSA-392499 Metabolism of proteins 4 R-HSA-73894 DNA Repair 2
Partners
FANCD2NFE2L1NFE2L3
Complex memberships
20S proteasome26S proteasome

Evidence

Reading pass · 11 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1996 PSMB3 is one of the beta-type subunits of the 20S proteasome, a large multicatalytic proteinase complex whose multiple peptidase activities operate through a novel threonine-based proteolytic mechanism; the 20S core assembles into the 26S complex with a 19S regulatory particle to degrade ubiquitinated proteins. Biochemical purification, structural analysis, and protease activity assays of the 20S and 26S proteasome complexes Annual review of biochemistry High 8811196
1997 The human PSMB3 gene (encoding the beta3 subunit, HsC10-II) was mapped by fluorescence in situ hybridization to chromosome band 2q35; unlike the interferon-inducible PSMB8/PSMB9 subunit genes clustered in the MHC, PSMB3 is independently located, consistent with independent transcriptional regulation of individual proteasome beta subunit genes. Fluorescence in situ hybridization (FISH) of genomic clones Genomics High 9344661
1999 The mouse ortholog of PSMB3 (C10-II) was cloned by cDNA isolation, and its protein identity was verified by 2D-NEPHGE-PAGE immunoblotting using antisera raised against the subunit, establishing it as one of the 17 subunits forming the mouse 20S proteasome core. cDNA cloning, two-dimensional NEPHGE-PAGE, immunoblotting with subunit-specific antisera Immunogenetics High 10436176
2002 Psmb3 was identified and chromosomally assigned to distal mouse chromosome 11 within a dense gene cluster syntenic to human chromosome 17q12, establishing the mouse genomic locus. Transgene-induced contig sequencing and cDNA selection Cytogenetic and genome research Medium 12438746
2007 siRNA-mediated depletion of PSMB3 (a 20S proteasome subunit) inhibited monoubiquitination and/or nuclear foci formation of FANCD2, demonstrating that proteasome function—specifically involving PSMB3—is required for activation of the Fanconi anemia DNA damage signaling pathway. siRNA knockdown of PSMB3 in human cells, immunofluorescence for FANCD2 foci, ubiquitination assays Cancer research Medium 17671210
2011 siRNA knockdown of PSMB3 in human airway epithelial cells increased susceptibility to AAV infection, placing PSMB3/proteasome function as a component of the subcellular barrier that restricts AAV virion trafficking or processing at the level of the secretory/ER-Golgi system. siRNA knockdown of PSMB3 combined with AAV infection efficiency assays in human airway epithelium models PLoS pathogens Medium 21625534
2011 In an RNAi screen of the druggable genome in multiple myeloma cells, silencing of PSMB3 synergistically potentiated growth inhibition by the proteasome inhibitor bortezomib, providing functional evidence that PSMB3 contributes to the proteolytic capacity required for myeloma cell survival under proteasome stress. Genome-wide siRNA screen (13,984 siRNAs) measuring proliferation in the presence of bortezomib; internal validation by proteasome subunit hits Blood Medium 21289309
2011 Psmb3 (endopeptidase) shares the same thymic expression profile as Prss16 (Tssp) in mouse cortical thymic epithelial cells, being induced in wild-type and repressed in Prss16-knockout mice, suggesting its participation in self-peptide generation for positive selection of CD4+ T lymphocytes. Microarray transcriptional profiling comparing wild-type and Prss16-knockout thymic tissue Molecular biology reports Low 21773946
2013 siRNA-mediated knockdown of PSMB3 in a human astrocytic cell line reduced CTG•CAG trinucleotide repeat expansions, demonstrating that the proteolytic activity of the 26S proteasome—specifically requiring PSMB3—drives repeat expansions in human cells. siRNA knockdown of PSMB3 in human astrocytic cells, quantitative trinucleotide repeat expansion assay; proteasome inhibitor controls confirmed proteolytic (not stress-response) mechanism Nucleic acids research Medium 23620289
2020 Double knockdown of transcription factors NFE2L1 and NFE2L3 in cancer cells significantly reduced basal expression of PSMB3 (along with six other proteasome genes), impairing basal proteasome activity; NFE2L3 suppresses NFE2L1 translation via induction of CPEB3, revealing that PSMB3 basal expression in cancer cells is maintained by an NFE2L1/NFE2L3-CPEB3 translational repression axis. Double siRNA knockdown of NFE2L1/NFE2L3, qRT-PCR and western blot for PSMB3 and other proteasome subunits, proteasome activity assays, polysome profiling for NFE2L1 mRNA Molecular and cellular biology Medium 32366381
2023 siRNA-mediated silencing of PSMB3 in human hepatocyte cell lines (HuH-7 and HepG2) was sufficient to suppress proteasome function and upregulate TRIB1 mRNA expression, demonstrating that PSMB3 activity is required to maintain basal proteasome function in hepatocytes and that its inhibition triggers transcriptional induction of TRIB1. siRNA knockdown of PSMB3, RT-qPCR for TRIB1 mRNA, western blot for protein levels and ubiquitylation; comparison with pharmacological proteasome inhibitors Scientific reports Medium 37291259

Source papers

Stage 0 corpus · 57 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
1996 Structure and functions of the 20S and 26S proteasomes. Annual review of biochemistry 2108 8811196
2002 Isolation of a human gene that inhibits HIV-1 infection and is suppressed by the viral Vif protein. Nature 1924 12167863
2002 Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences. Proceedings of the National Academy of Sciences of the United States of America 1479 12477932
2009 Recognition and processing of ubiquitin-protein conjugates by the proteasome. Annual review of biochemistry 1398 19489727
2009 Defining the human deubiquitinating enzyme interaction landscape. Cell 1282 19615732
2003 Broad antiretroviral defence by human APOBEC3G through lethal editing of nascent reverse transcripts. Nature 1236 12808466
2003 DNA deamination mediates innate immunity to retroviral infection. Cell 1150 12809610
2015 The BioPlex Network: A Systematic Exploration of the Human Interactome. Cell 1118 26186194
2017 Architecture of the human interactome defines protein communities and disease networks. Nature 1085 28514442
2015 A human interactome in three quantitative dimensions organized by stoichiometries and abundances. Cell 1015 26496610
2003 Induction of APOBEC3G ubiquitination and degradation by an HIV-1 Vif-Cul5-SCF complex. Science (New York, N.Y.) 1006 14564014
2014 A proteome-scale map of the human interactome network. Cell 977 25416956
2003 The cytidine deaminase CEM15 induces hypermutation in newly synthesized HIV-1 DNA. Nature 912 12808465
2013 Landscape of the PARKIN-dependent ubiquitylome in response to mitochondrial depolarization. Nature 870 23503661
2020 A reference map of the human binary protein interactome. Nature 849 32296183
2018 VIRMA mediates preferential m6A mRNA methylation in 3'UTR and near stop codon and associates with alternative polyadenylation. Cell discovery 829 29507755
2003 The antiretroviral enzyme APOBEC3G is degraded by the proteasome in response to HIV-1 Vif. Nature medicine 798 14528300
2003 Species-specific exclusion of APOBEC3G from HIV-1 virions by Vif. Cell 763 12859895
2007 Large-scale mapping of human protein-protein interactions by mass spectrometry. Molecular systems biology 733 17353931
2021 Dual proteome-scale networks reveal cell-specific remodeling of the human interactome. Cell 705 33961781
2012 A census of human soluble protein complexes. Cell 689 22939629
2003 HIV-1 Vif protein binds the editing enzyme APOBEC3G and induces its degradation. Nature medicine 679 14528301
2011 Phylogenetic-based propagation of functional annotations within the Gene Ontology consortium. Briefings in bioinformatics 656 21873635
2008 Large-scale proteomics and phosphoproteomics of urinary exosomes. Journal of the American Society of Nephrology : JASN 607 19056867
2003 HIV-1 Vif blocks the antiviral activity of APOBEC3G by impairing both its translation and intracellular stability. Molecular cell 607 14527406
2003 Hypermutation of HIV-1 DNA in the absence of the Vif protein. Science (New York, N.Y.) 570 12750511
2017 Anticancer sulfonamides target splicing by inducing RBM39 degradation via recruitment to DCAF15. Science (New York, N.Y.) 533 28302793
2006 Hsp90 cochaperone Aha1 downregulation rescues misfolding of CFTR in cystic fibrosis. Cell 517 17110338
2011 Mapping the NPHP-JBTS-MKS protein network reveals ciliopathy disease genes and pathways. Cell 507 21565611
2004 The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC). Genome research 438 15489334
2008 Identification of proteomic differences in asthenozoospermic sperm samples. Human reproduction (Oxford, England) 215 18281682
2007 Proteasome function is required for DNA damage response and fanconi anemia pathway activation. Cancer research 178 17671210
2011 RNAi screen of the druggable genome identifies modulators of proteasome inhibitor sensitivity in myeloma including CDK5. Blood 91 21289309
2020 NFE2L1 and NFE2L3 Complementarily Maintain Basal Proteasome Activity in Cancer Cells through CPEB3-Mediated Translational Repression. Molecular and cellular biology 42 32366381
2013 The expression of inflammatory genes is upregulated in peripheral blood of patients with type 1 diabetes. Diabetes care 42 23637351
2022 Prioritization of Drug Targets for Neurodegenerative Diseases by Integrating Genetic and Proteomic Data From Brain and Blood. Biological psychiatry 41 36759259
2011 AAV exploits subcellular stress associated with inflammation, endoplasmic reticulum expansion, and misfolded proteins in models of cystic fibrosis. PLoS pathogens 40 21625534
1999 The complete primary structure of mouse 20S proteasomes. Immunogenetics 34 10436176
2018 Impaired Proteasomal Function in Human Osteoarthritic Chondrocytes Can Contribute to Decreased Levels of SOX9 and Aggrecan. Arthritis & rheumatology (Hoboken, N.J.) 24 29457374
2021 The Silence of PSMC6 Inhibits Cell Growth and Metastasis in Lung Adenocarcinoma. BioMed research international 23 34239933
2021 WGCNA-Based Identification of Hub Genes and Key Pathways Involved in Nonalcoholic Fatty Liver Disease. BioMed research international 20 34938809
2017 RNA Sequencing of Murine Norovirus-Infected Cells Reveals Transcriptional Alteration of Genes Important to Viral Recognition and Antigen Presentation. Frontiers in immunology 16 28848558
1997 Genetic relationships of the genes encoding the human proteasome beta subunits and the proteasome PA28 complex. Genomics 14 9344661
2013 Chromosomal aneuploidy affects the global proteome equilibrium of colorectal cancer cells. Analytical cellular pathology (Amsterdam) 11 24464829
2021 Transcriptome Analysis Reveals Possible Immunomodulatory Activity Mechanism of Chlorella sp. Exopolysaccharides on RAW264.7 Macrophages. Marine drugs 8 33919822
2023 Proteasome β3 subunit (PSMB3) controls female reproduction by promoting ecdysteroidogenesis during sexual maturation in Bactrocera dorsalis. Insect biochemistry and molecular biology 7 37172766
2021 Effectiveness of bortezomib and temozolomide for eradication of recurrent human glioblastoma cells, resistant to radiation. Progress in brain research 7 34689859
2013 The 26S proteasome drives trinucleotide repeat expansions. Nucleic acids research 7 23620289
2023 Quantitative proteomics analysis reveals the key proteins related to semen quality in Niangya yaks. Proteome science 5 37875878
2011 Transcription profiling of Prss16 (Tssp) can be used to find additional peptidase genes that are candidates for self-peptide generation in the thymus. Molecular biology reports 5 21773946
2002 Mutagenic transgene insertion into a region of high gene density and multiple linkage disruptions on mouse chromosome 11. Cytogenetic and genome research 5 12438746
2024 Diminished expression of the ubiquitin-proteasome system in early treatment-naïve patients with rheumatoid arthritis and concomitant type 2 diabetes may be linked to IL-1 pathway hyper-activity; results from PEAC cohort. Arthritis research & therapy 4 39342401
2023 Regulation of TRIB1 abundance in hepatocyte models in response to proteasome inhibition. Scientific reports 4 37291259
2025 Five autoantibodies identified from immune complexes as breast cancer biomarkers. Frontiers in immunology 1 40766308
2026 Machine learning-based identification of potential diagnostic signatures in spinal cord injury. Spinal cord 0 41760790
2025 Identification of exosome-related genes in Alzheimer's disease: Evidence from transcriptomic and Mendelian randomization analyses. Journal of Alzheimer's disease : JAD 0 40899950
2025 The Proteomic Profiling of Circulating Extracellular Vesicles of Western Diet and Chemical-Induced Murine MASH Model. The Kaohsiung journal of medical sciences 0 40923709