proteasome storage granule

GO:0034515 · Inclusion · Inclusion body · Proposed

A cytoplasmic, membrane-free accumulation of proteasome core and regulatory particles observed as discrete foci during cellular quiescence. [GO:0034515]

Image (not hosted — OTHER): PMC2396804.1 fig2

Figure 2. Core, lid and base markers colocalize in budding-yeast PSGs after four days of culture (A); a core-marker time course tracks redistribution (B). Scale bars are 2 micrometers. Colocalization does not establish holoenzyme assembly. FLUORESCENCE · Saccharomyces cerevisiae (NCBITaxon:4932) · Damien Laporte, Bénédicte Salin, Bertrand Daignan-Fornier and Isabelle Sagot (2008), Journal of Cell Biology; CC BY-NC-SA 3.0, via PubMed Central. · OTHER · source: PMC PMC2396804.1 fig2 · DOI:10.1083/jcb.200711154

Synonyms: PSG

Part of: GO:0005737 — cytoplasm (no local record)

Has part: proteasome core complex (GO:0005839); GO:0005838 — proteasome regulatory particle (no local record)

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Genes	Essential	Role
proteasome core complex	Protein complex	part of	`GO:0005839`		UNKNOWN	Proteolytic particle represented by the 20S core in the yeast studies. Listing core and regulatory particles separately does not assert that they are physically dissociated within every intact granule. `DOI:10.1083/jcb.200711154` Figures 1-2 localize core subunits to PSGs by immunogold and fluorescence. `DOI:10.1091/mbc.E17-03-0162` Figure 5 detects core subunits in enriched cross-linked PSG preparations.
proteasome regulatory particle	Protein complex	part of	`GO:0005838` — proteasome regulatory particle		UNKNOWN	The 19S particle is represented by both base and lid markers in yeast PSGs. Marker colocalization alone does not determine holoenzyme assembly state. `DOI:10.1083/jcb.200711154` Figure 2 compares core, base and lid markers in the same foci. `DOI:10.1091/mbc.E17-03-0162` Figure 5 detects regulatory-particle subunits in enriched PSG preparations.
Proteasome activator complex subunit 4	Protein	part of	`InterPro:IPR035309`	BLM10	UNKNOWN	Activator family represented by PSG-associated Blm10 in budding yeast; residence is not generalized to every family member or experimental condition. `DOI:10.1091/mbc.E17-03-0162` Figures 4A and 5D support residence independently of the retracted 2018 study. `InterPro:IPR035309` Native complete six-entry P43583 match set contains this family; domain and superfamily matches were not used as whole-protein identities.
Ubiquitin carboxyl-terminal hydrolase 14-like	Protein	part of	`InterPro:IPR044635`	UBP6	UNKNOWN	Proteasome-associated hydrolase family represented by Ubp6 colocalization with PSGs in budding yeast. Family identity does not imply universal PSG residence. `DOI:10.1091/mbc.E17-03-0162` Figure 4B supports residence; deletion phenotypes alone are not the basis for component membership or a universal assembly requirement. `InterPro:IPR044635` Native complete seven-entry P43593 match set identifies this family.
unconjugated ubiquitin	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	UBI4	UNKNOWN	Free ubiquitin enriched in the tested cross-linked PSG preparations. UBI4 is an experimentally used precursor source, not the only ubiquitin gene or a claim that intact polyubiquitin precursor chains constitute PSG cargo. `DOI:10.1091/mbc.E17-03-0162` Figure 5E supports enrichment of free ubiquitin; weak polyubiquitin detection is not a universal exclusion rule for every PSG condition.

Organism-specific protein examples

Named proteins in which each component's role was established, with the organism the evidence comes from. The component above is the taxon-agnostic family; these are the specific entries behind it.

Proteasome activator complex subunit 4

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P43583`	Proteasome activator BLM10	BLM10	Saccharomyces cerevisiae S288C (`NCBITaxon:559292`)	REVIEWED
Role and evidence (2 references) Reference-sequence example for the Blm10 colocalization and enrichment assays; the paper's BY4741 and WCGa experiments are not reassigned to S288C. `UniProtKB:P43583` Native reviewed entry verifies accession, name, gene and reference taxon. `DOI:10.1091/mbc.E17-03-0162` Figures 4A and 5D support localization and biochemical enrichment.

Ubiquitin carboxyl-terminal hydrolase 14-like

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P43593`	Ubiquitin carboxyl-terminal hydrolase 6	UBP6	Saccharomyces cerevisiae S288C (`NCBITaxon:559292`)	REVIEWED
Role and evidence (2 references) Reference-sequence example for the Ubp6-GFP localization assay, not a claim that the experiment used the reference strain itself. `UniProtKB:P43593` Native reviewed entry verifies accession, name, gene and reference taxon. `DOI:10.1091/mbc.E17-03-0162` Figure 4B compares Ubp6-GFP and Pre2-mCherry in quiescent cells.

unconjugated ubiquitin

Accession	Protein	Gene	Organism	Entry
`UniProtKB:P0CG63`	Polyubiquitin	UBI4	Saccharomyces cerevisiae S288C (`NCBITaxon:559292`)	REVIEWED
Role and evidence (2 references) Precursor reference sequence whose processed ubiquitin product is relevant. Figure 4C uses a diglycine-deleted GFP reporter; this engineered reporter is not identical to native P0CG63 or proof of unprocessed precursor residence. `UniProtKB:P0CG63` Native reviewed entry explicitly identifies a precursor containing ubiquitin. `DOI:10.1091/mbc.E17-03-0162` Figures 4C and 5E distinguish the tagged processed product from free ubiquitin detected in enriched preparations.

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — BY4741/BY4742/BY4743-derived strains provide localization and refeeding assays. [DOI:10.1083/jcb.200711154]
NCBITaxon:4896 Schizosaccharomyces pombe — Figure 5 follows endogenous Pad1-GFP foci after four days of culture and their mobilization after refeeding, including cycloheximide-treated cells. [DOI:10.1083/jcb.200711154]
NCBITaxon:559292 Saccharomyces cerevisiae S288C — Reference-sequence taxon for protein examples, not a reassignment of all imaging or biochemical experiments to this strain. [UniProtKB:P43583]

Functions

reversible proteasome storage — Concentrates proteasome material during quiescence for subsequent mobilization. This does not assert protection from autophagic degradation.
- DOI:10.1083/jcb.200711154 Figures 4-5 test refeeding with water and translation-inhibition controls.

Mechanism graphs

Refeeding mobilizes PSG-associated proteasome material (DISASSEMBLY)

Subject	Predicate	Object	Evidence
Transfer to fresh YPD	induces	Loss of PSG-localized Pre6-GFP foci	`DOI:10.1083/jcb.200711154` Figure 4B-C compares refeeding with and without cycloheximide; Figure 4A supplies the water-transfer control.
Transfer to fresh YPD	induces	Nuclear relocalization of Pre6-GFP	`DOI:10.1083/jcb.200711154` Figure 4 follows redistribution to the nuclear periphery and nucleus.

Discussions

INTERPRETATION (RESOLVED): Exclude the retracted 2018 study and derivative commentary from positive support. Ontology citation chains can retain secondary accounts of withdrawn work.
CURATION_TODO (OPEN): Reconcile in situ PSG architecture with older extract-based assembly assays. Colocalized subunits and dissociated particles in lysates do not uniquely establish assembly state inside living-cell granules.
INTERPRETATION (RESOLVED): Separate experimentally observed residents from indirect genetic modifiers. A deletion phenotype or a different reversible focus is not PSG membership.
CURATION_TODO (OPEN): Resolve an exact source-neutral identifier for unconjugated mature ubiquitin. Domains and a family including other ubiquitin-like proteins are broader than the curated component.
INTERPRETATION (RESOLVED): Keep PSG distinct from individual proteasomes and other protein inclusions. Shared components or transient proximity do not establish identity.

Evidence

GO:0034515 Native QuickGO verifies active cellular-component identity, related-scope PSG abbreviation, membraneless-organelle parent and cytoplasmic parthood.
DOI:10.1083/jcb.200711154 Laporte et al. (2008), PMID 18504300, PMC2396804.1. Native metadata reports no retraction. Main Results, figure captions and relevant strain/microscopy methods inspected; Figure 2 pixels inspected. Supplemental files were not inspected.
DOI:10.1091/mbc.E17-03-0162 Gu et al. (2017), PMID 28768827, PMC5597321.1. Native metadata reports no retraction. Main composition, localization, ubiquitin-overexpression and native-gel Results, figure captions and strain methods inspected. Supplemental files and raw proteomics were not independently inspected.
DOI:10.1016/j.cell.2025.12.035 Tang et al. (2026), PMID 41605212. Primary abstract reports inactive, doubly capped 26S proteasomes organized into trimer-based paracrystalline arrays by in situ cryo-ET. Only abstract and bibliographic metadata were read; publisher full text and the Max Planck repository PDF returned 403. No detailed assembly graph, quantitative property or accession is inferred from the abstract.

Curation history

2026-10-05T12:40:28Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-10-05T12:42:16Z codex · EXPANDED_RECORD — Added five component classes, three reference protein examples, bounded yeast evidence, a recovery graph, explicit retraction/architecture provenance and an inspected link-only figure.
2026-10-05T12:44:38Z codex · CORRECTED_ATTRIBUTION — Corrected Salin's given name from native JATS author metadata before publication.

Source: data/structures/inclusion/proteasome_storage_granule.yaml