Affinage

POMP

Proteasome maturation protein · UniProt Q9Y244

Length
141 aa
Mass
15.8 kDa
Annotated
2026-06-10
29 papers in source corpus 15 papers cited in narrative 17 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 7/7 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

POMP (proteasome maturation protein / hUMP1) is a transiently acting assembly chaperone that drives biogenesis of the 20S proteasome core particle (PMID:10926487, PMID:17948026). Present exclusively in precursor (16S/15S) complexes and absent from mature 20S proteasomes, POMP associates with ER membranes, binds assembled α1-7 rings, and recruits β-subunits stepwise to mediate precursor formation (PMID:10926487, PMID:17948026). Its N-terminal region directly contacts the β7 (Pre4) propeptide, and this interaction is the critical step that drives dimerization of half-proteasomes into the 20S core; loss of this contact causes massive accumulation of 15S precursors that is bypassed by β7 overexpression (PMID:17431397, PMID:35204754). Upon completion of the β-ring and autocatalytic propeptide cleavage, POMP is dissociated and degraded as the mature core is sealed. POMP is an intrinsically disordered protein (PMID:24688736, PMID:24065419). POMP-dependent proteasome assembly supports antioxidant defense (PMID:17349762), NF-κB signaling downstream of DNA damage (PMID:26615982), and terminal epidermal differentiation including profilaggrin processing (PMID:22235297). Its abundance is controlled by interferon-γ induction (PMID:10926487), direct transcriptional induction by NRF3 to drive ubiquitin-independent degradation of p53 and Rb in tumors (PMID:32123008), and post-transcriptional repression by miR-101 whose loss impairs assembly and triggers p53 accumulation and cell-cycle arrest (PMID:26145175). A POMP 5'UTR mutation underlies the epidermal disorder KLICK (PMID:20226437), and de novo heterozygous frameshift variants that escape nonsense-mediated decay act dominant-negatively to perturb assembly, causing POMP-related autoinflammation and immune dysregulation disease (PRAID) (PMID:29805043). A moonlighting role in which POMP accumulates in the nucleolus to direct a protective transcriptional program has been described in preprint form.

Mechanistic history

Synthesis pass · year-by-year structured walk · 11 steps
  1. 2000 High

    Established that the human Ump1 homologue is a transient assembly chaperone rather than a structural proteasome subunit, defining its core mechanistic identity.

    Evidence 2D gel identification, fractionation/immunoblot, and T2 cell mutagenesis showing POMP only in 16S precursors, not mature 20S, with IFN-γ inducibility

    PMID:10926487

    Open questions at the time
    • Did not map which proteasome subunits POMP contacts
    • Mechanism of POMP degradation upon maturation not resolved
  2. 2007 High

    Resolved where and how POMP acts during assembly, placing it at the ER membrane binding α-rings and recruiting β-subunits stepwise, and defined the yeast orthologue as an assembly checkpoint factor.

    Evidence Precursor-specific antibodies, fractionation, Co-IP, immunofluorescence in human cells; genetic epistasis and β7 overproduction bypass in yeast

    PMID:17431397 PMID:17948026

    Open questions at the time
    • Did not identify the direct β-subunit contact responsible for the checkpoint
    • Structural basis of α-ring binding unknown
  3. 2007 Medium

    Showed that raising POMP levels increases functional proteasome and oxidative-stress resistance, linking chaperone abundance to cellular proteostatic capacity.

    Evidence Stable overexpression in fibroblasts with proteasome activity and viability assays under oxidative stress

    PMID:17349762

    Open questions at the time
    • Single overexpression approach
    • Did not separate antioxidant effect from general proteasome upregulation
  4. 2013 Medium

    Determined that POMP/Ump1 is intrinsically disordered and can self-associate via a single cysteine, explaining its flexible, transient engagement with assembly intermediates.

    Evidence Recombinant purification, size-exclusion, disulfide analysis, and NMR backbone assignments of yeast Ump1

    PMID:24065419 PMID:24688736

    Open questions at the time
    • No bound-state structure on precursor complexes
    • Functional relevance of disulfide-linked oligomers in vivo unclear
  5. 2015 High

    Connected POMP levels to cell proliferation and drug resistance, showing that miR-101 repression of POMP limits proteasome assembly and that POMP knockdown overcomes bortezomib resistance.

    Evidence miRNA targeting, knockdown/rescue, proteasome activity assays, p53/CDK-inhibitor blots, cell-cycle and bortezomib resistance assays in tumor cells

    PMID:26145175

    Open questions at the time
    • Did not test miR-101/POMP axis in vivo
    • Other miR-101 targets may contribute to phenotype
  6. 2015 Medium

    Linked POMP-dependent proteasome function to DNA-damage-induced NF-κB signaling, broadening its role beyond bulk proteostasis.

    Evidence Whole-exome sequencing and wild-type POMP complementation rescuing NF-κB signaling in patient-derived cells

    PMID:26615982

    Open questions at the time
    • Single patient and single complementation approach
    • Molecular step connecting proteasome assembly to NF-κB not defined
  7. 2018 High

    Defined a dominant-negative disease mechanism in which NMD-escaping truncated POMP perturbs assembly, establishing POMP haploinsufficiency-independent pathology in PRAID.

    Evidence Whole-exome sequencing, mRNA/NMD analysis, and proteasome assembly assays in two unrelated patients

    PMID:29805043

    Open questions at the time
    • How truncated POMP poisons assembly mechanistically not resolved
    • Tissue-specific severity not explained
  8. 2020 High

    Identified NRF3 as a direct transcriptional inducer of POMP that increases 20S assembly to degrade p53 and Rb via ubiquitin-independent proteolysis, linking POMP to oncogenic proteostasis.

    Evidence NRF3 transcription assays, POMP overexpression/knockdown, protein stability assays with proteasome and E1 inhibitors

    PMID:32123008

    Open questions at the time
    • Whether 20S degrades p53/Rb directly or via accessory factors not fully resolved
    • In vivo tumor dependence on NRF3-POMP axis not tested here
  9. 2022 High

    Pinpointed the N-terminal Ump1 domain–β7 propeptide interaction as the trigger for half-proteasome dimerization, providing the molecular basis of the assembly checkpoint.

    Evidence In vitro pulldown, deletion/domain mapping, intermediate isolation, and β7 overexpression rescue in yeast

    PMID:35204754

    Open questions at the time
    • Human POMP–β7 interaction not directly demonstrated
    • Structure of the POMP–β7 interface unresolved
  10. 2024 Medium

    Provided a structural choreography of human assembly showing concerted POMP/PAC1/PAC2 dissociation coupled to β propeptide cleavage upon dimerization.

    Evidence CRISPR endogenous tagging and cryo-EM of assembly intermediates (preprint)

    Open questions at the time
    • Preprint, not peer-reviewed
    • Disordered regions of POMP not fully resolved in maps
  11. 2025 Medium

    Proposed a moonlighting function in which POMP accumulates in the nucleolus under proteasome stress to drive a protective transcriptional program independent of its assembly role.

    Evidence Live-cell imaging, POMP interactor proteomics, transcriptomics, and HSF1/ROS perturbation (preprint)

    Open questions at the time
    • Preprint, not peer-reviewed
    • Direct transcriptional/RNA-binding activity of POMP not demonstrated
    • Relationship to its chaperone function unclear

Open questions

Synthesis pass · forward-looking unresolved questions
  • How POMP integrates its canonical proteasome assembly role with the proposed nucleolar transcriptional function, and the structural basis of the human POMP–β7 contact, remain unresolved.
  • No high-resolution structure of human POMP bound to a precursor complex
  • Mechanism of nucleolar targeting and any RNA/transcription activity uncharacterized

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0098772 molecular function regulator activity 3 GO:0140096 catalytic activity, acting on a protein 2
Localization
GO:0005730 nucleolus 1 GO:0005783 endoplasmic reticulum 1 GO:0005829 cytosol 1
Pathway
R-HSA-1852241 Organelle biogenesis and maintenance 3 R-HSA-392499 Metabolism of proteins 3 R-HSA-1643685 Disease 2
Partners
HSF1NRF3PAC1PAC2PSMA7PSMB5PSMB7
Complex memberships
20S proteasome precursor (16S/15S) complex

Evidence

Reading pass · 17 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2000 POMP (hUmp1) is a human homologue of yeast Ump1 that is present exclusively in 16S precursor complexes and not in mature 20S proteasomes, establishing it as a transiently acting assembly chaperone. Interferon-gamma treatment induces POMP expression, and absence of the β5 propeptide delays proteasome maturation and causes accumulation of precursor complexes with increased POMP levels. 2D gel identification, fractionation/immunoblot, northern blot, T2 cell mutagenesis studies Journal of molecular biology High 10926487
2007 POMP facilitates major steps of 20S proteasome core complex formation at the endoplasmic reticulum (ER): it interacts with ER membranes, binds to assembled α1-7 rings, recruits β-subunits stepwise, and mediates association of precursor complexes with the ER membrane. Precursor complex-specific antibodies, subcellular fractionation, co-immunoprecipitation, immunofluorescence/confocal microscopy EMBO reports High 17948026
2007 Yeast Ump1 (POMP orthologue) acts as a checkpoint factor during 20S proteasome assembly: it is present in precursor complexes (15S PC) and is required for efficient β-subunit processing; overproduction of β7 (Pre4) overcomes Ump1-dependent assembly checkpoint and stabilizes the precursor dimer. Assembly proceeds stepwise into precursor dimers; Ump1 co-exists in intermediates with the Pba1-Pba2 complex. Genetic epistasis, beta-subunit overproduction bypass, isolation of assembly intermediates, immunoprecipitation The EMBO journal High 17431397
2006 POMP elutes from a calibrated size-exclusion column at ~64 kDa (consistent with a tetramer of the 16 kDa monomer), suggesting oligomerization. Immunofluorescence/confocal microscopy localized POMP to both the cytoplasm and the nucleus. Gel filtration chromatography, immunofluorescence/confocal microscopy International journal of biological macromolecules Low 16624403
2007 Overexpression of hUMP1/POMP in human fibroblasts increases levels of functional proteasome and enhances the capacity of cells to cope with oxidative stressors, demonstrating that POMP promotes proteasome assembly and antioxidant defense through increased proteasome activity. Stable overexpression in fibroblasts, proteasome activity assays, cell viability assays under oxidative stress Experimental gerontology Medium 17349762
2010 A single-nucleotide deletion at position c.-95 in the POMP 5' UTR causes a transcriptional switch to longer 5' UTR transcript variants in keratinocytes from KLICK patients, leading to altered epidermal distribution of POMP, proteasome subunits α7 and β5, and ER stress marker CHOP, establishing POMP as essential for proteasome assembly in terminally differentiating epidermis. Homozygosity mapping, Sanger sequencing, immunohistochemistry of patient skin biopsies, northern/RT-PCR analysis American journal of human genetics Medium 20226437
2012 siRNA knockdown of POMP in epidermal air-liquid interface cultures reduces proteasome subunit levels, causes aberrant profilaggrin-to-filaggrin processing, and upon prolonged silencing induces CHOP expression, activating the unfolded protein response/ER stress pathway, linking POMP-dependent proteasome assembly to epidermal terminal differentiation. siRNA knockdown in organotypic keratinocyte cultures, immunohistochemistry, western blot, ER stress reporter (CHOP expression) PloS one Medium 22235297
2013 Recombinant yeast Ump1 (POMP orthologue) purified from E. coli forms multiple oligomeric species via intermolecular disulfide bonds involving its sole cysteine residue, and biophysical characterization (NMR, bioinformatics) reveals it is an intrinsically disordered protein. Recombinant protein purification, size-exclusion chromatography, disulfide bond analysis, NMR chemical shift analysis, bioinformatics Computational and structural biotechnology journal Medium 24688736
2013 NMR backbone chemical shift assignments of yeast Ump1 confirm it is an intrinsically disordered protein largely devoid of secondary structure elements in solution. NMR spectroscopy (backbone 1H, 13C, 15N assignments) Biomolecular NMR assignments Medium 24065419
2015 miR-101 directly targets POMP mRNA, reducing POMP protein levels, impairing 20S proteasome assembly and activity, causing accumulation of p53 and CDK inhibitors, cell cycle arrest, and apoptosis. miR-101-resistant POMP restores proteasome substrate turnover and tumor cell growth. POMP knockdown is sufficient to overcome bortezomib resistance in tumor cells. miRNA targeting assays, POMP knockdown/rescue experiments, proteasome activity assays, western blot for p53 and CDK inhibitors, cell cycle and apoptosis assays, bortezomib resistance assays Molecular cell High 26145175
2015 POMP is required for efficient NF-κB signaling downstream of DNA damage; complementation with wild-type POMP rescued defective NF-κB signaling in patient-derived cells carrying a de novo POMP mutation. Whole-exome sequencing, Sanger sequencing, complementation assay with wild-type POMP, NF-κB signaling assays in patient-derived cells Human mutation Medium 26615982
2017 POMP binds to 20S precursor complexes in psoriatic skin and is overexpressed in lesional epidermis, supporting increased POMP-mediated proteasome assembly. POMP silencing in HaCaT keratinocytes inhibits cell proliferation, induces apoptosis via proteasome assembly inhibition, and decreases expression of differentiation markers keratin 10 and involucrin. Native gel electrophoresis, western blot, immunohistochemistry, siRNA knockdown, differentiation assays Journal of dermatological science Medium 28728908
2018 De novo heterozygous frameshift variants in the penultimate exon of POMP escape nonsense-mediated mRNA decay and produce a truncated protein that perturbs proteasome assembly by a dominant-negative mechanism, causing PRAID (POMP-related autoinflammation and immune dysregulation disease) with combined immunodeficiency and autoinflammation. Whole-exome sequencing, mRNA/NMD analysis, patient cell functional studies, proteasome assembly assays American journal of human genetics High 29805043
2020 NRF3 directly induces POMP gene expression in cancer cells, increasing 20S proteasome assembly; the resulting 20S proteasomes degrade p53 and retinoblastoma (Rb) proteins via ubiquitin-independent proteolysis, promoting tumor growth and resistance to bortezomib (but not to the E1 inhibitor TAK-243). NRF3 ChIP/transcription assays, POMP overexpression/knockdown, protein stability assays with proteasome inhibitors, cell viability assays, proteasome assembly assays Molecular and cellular biology High 32123008
2022 The N-terminal domain of Ump1 (yeast POMP orthologue) directly interacts with the propeptide of the β7 subunit in vitro, and this interaction is critical for β7 recruitment into the 15S precursor complex, which drives dimerization of half-proteasomes into 20S core particles. Deletion of the first 16 Ump1 residues causes massive accumulation of 15S PC; β7 overexpression can bypass the resulting growth defect. In vitro pulldown/direct interaction assay, genetic epistasis (deletion/mutation analysis), proteasome intermediate isolation, β7 overexpression rescue Biomolecules High 35204754
2024 Cryo-EM of endogenously tagged human proteasome assembly chaperones reveals that PAC1-4 stabilize an early α-ring intermediate; upon PAC3/PAC4 dissociation and PAC1 N-terminal tail rearrangement, β-ring assembly proceeds. Completion of the β-ring and half-proteasome dimerization repositions lysine K33, triggering β pro-peptide cleavage and concerted dissociation of POMP together with PAC1/PAC2 to yield mature 20S proteasomes. CRISPR/Cas9 endogenous tagging of chaperones, cryo-EM structural analysis of assembly intermediates bioRxivpreprint Medium
2025 Upon proteasome disruption, POMP rapidly accumulates in the nucleolus in a manner dependent on HSF1 and reactive oxygen species (ROS). Proteomic analysis of POMP interactors in this context revealed RNA processing factors, and transcriptomic profiling showed that nucleolar POMP orchestrates a protective transcriptional program, revealing a moonlighting role as a stress-induced transcriptional regulator independent of its proteasome assembly chaperone function. Live cell imaging (nucleolar accumulation), proteomics (POMP interactors), transcriptomics, HSF1 and ROS perturbation experiments bioRxivpreprint Medium

Source papers

Stage 0 corpus · 29 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2007 beta-Subunit appendages promote 20S proteasome assembly by overcoming an Ump1-dependent checkpoint. The EMBO journal 134 17431397
2018 Heterozygous Truncating Variants in POMP Escape Nonsense-Mediated Decay and Cause a Unique Immune Dysregulatory Syndrome. American journal of human genetics 127 29805043
2000 Characterisation of the newly identified human Ump1 homologue POMP and analysis of LMP7(beta 5i) incorporation into 20 S proteasomes. Journal of molecular biology 103 10926487
2022 SWOG 1318: A Phase II Trial of Blinatumomab Followed by POMP Maintenance in Older Patients With Newly Diagnosed Philadelphia Chromosome-Negative B-Cell Acute Lymphoblastic Leukemia. Journal of clinical oncology : official journal of the American Society of Clinical Oncology 97 35157496
2007 The proteasome maturation protein POMP facilitates major steps of 20S proteasome formation at the endoplasmic reticulum. EMBO reports 90 17948026
2005 Ump1 extends yeast lifespan and enhances viability during oxidative stress: central role for the proteasome? Free radical biology & medicine 69 16337885
2015 MicroRNA-101 Suppresses Tumor Cell Proliferation by Acting as an Endogenous Proteasome Inhibitor via Targeting the Proteasome Assembly Factor POMP. Molecular cell 63 26145175
2010 A single-nucleotide deletion in the POMP 5' UTR causes a transcriptional switch and altered epidermal proteasome distribution in KLICK genodermatosis. American journal of human genetics 62 20226437
2007 Overexpression of hUMP1/POMP proteasome accessory protein enhances proteasome-mediated antioxidant defence. Experimental gerontology 50 17349762
2020 NRF3-POMP-20S Proteasome Assembly Axis Promotes Cancer Development via Ubiquitin-Independent Proteolysis of p53 and Retinoblastoma Protein. Molecular and cellular biology 39 32123008
2005 RNA interference toward UMP1 induces proteasome inhibition in Saccharomyces cerevisiae: evidence for protein oxidation and autophagic cell death. Free radical biology & medicine 29 15607905
2013 Biochemical and biophysical characterization of recombinant yeast proteasome maturation factor ump1. Computational and structural biotechnology journal 23 24688736
1975 Acute lymphoblastic leukaemia: cyclical chemotherapy with three combinations of four drugs (COAP-POMP-CART regimen). British medical journal 22 1060502
2015 MCM3AP and POMP Mutations Cause a DNA-Repair and DNA-Damage-Signaling Defect in an Immunodeficient Child. Human mutation 20 26615982
2012 siRNA silencing of proteasome maturation protein (POMP) activates the unfolded protein response and constitutes a model for KLICK genodermatosis. PloS one 20 22235297
2006 Possible tetramerisation of the proteasome maturation factor POMP/proteassemblin/hUmp1 and its subcellular localisation. International journal of biological macromolecules 18 16624403
2013 Backbone ¹H, ¹³C and ¹⁵N assignments of yeast Ump1, an intrinsically disordered protein that functions as a proteasome assembly chaperone. Biomolecular NMR assignments 16 24065419
2000 Expression of UMP1 is inducible by DNA damage and required for resistance of S. cerevisiae cells to UV light. Current genetics 16 10975253
2023 Regulation of symbiotic interactions and primitive lichen differentiation by UMP1 MAP kinase in Umbilicaria muhlenbergii. Nature communications 12 37914724
2017 The proteasome maturation protein POMP increases proteasome assembly and activity in psoriatic lesional skin. Journal of dermatological science 12 28728908
2007 The spectrum of spontaneous mutations caused by deficiency in proteasome maturase Ump1 in Saccharomyces cerevisiae. Current genetics 10 17909815
2000 Proteasome mutants, pre4-2 and ump1-2, suppress the essential function but not the mitochondrial RNase P function of the Saccharomyces cerevisiae gene RPM2. Genetics 10 10757750
2020 KLICK Syndrome Linked to a POMP Mutation Has Features Suggestive of an Autoinflammatory Keratinization Disease. Frontiers in immunology 8 32425927
2022 Interaction with the Assembly Chaperone Ump1 Promotes Incorporation of the β7 Subunit into Half-Proteasome Precursor Complexes Driving Their Dimerization. Biomolecules 6 35204754
2015 Blocking Cancer Growth with Less POMP or Proteasomes. Molecular cell 6 26186288
2019 Expression analysis of proteasome maturation protein (POMP) gene in Liaoning Cashmere goat. Animal biotechnology 3 30957645
2013 Effect of proton pomp inhibitor (PPI : Rabeprazole) on reflux esophagitis after endoscopic injection sclerotherapy (EIS), a randomized control study (24 hour-pH monitoring). Fukuoka igaku zasshi = Hukuoka acta medica 2 24693675
2021 Phylogenetic and molecular analysis based on genes 16S-rRNA, OMPA and POMP to identify Chlamydia abortus infection occurrence at the milk samples of goats and sheep in west Azerbaijan of Iran. Iranian journal of microbiology 1 34557276
2015 [Effect of H2-receptor antagonist and proton pomp inhibitor on the treatment of acid-related disease]. Nihon rinsho. Japanese journal of clinical medicine 0 26165073

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