GO:0034515 proteasome storage granule: Components, Assembly and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0034515 proteasome storage granule (PSG) is a cytoplasmic, dot-like aggregation of proteasome core protease (CP) and regulatory particle (RP) complexes that forms when cells enter quiescence.
• PSG formation is reversible and is triggered by nutrient limitation, carbon starvation, acetic acid exposure, and entry into stationary phase.
• PSGs protect proteasomes from autophagic degradation, allowing rapid proteasome reactivation when growth conditions improve.
• Mitochondrial respiration and kinase signaling pathways regulate PSG assembly and disassembly.
• PSG biology is linked to proteasome homeostasis, microautophagy, and nuclear transport of proteasomes.
• Studying PSGs requires combining live-cell imaging, proteomics, and CRISPR-based genetic models to dissect the underlying regulatory network.
Description
The proteasome storage granule (PSG), annotated as GO:0034515, is a conserved cytoplasmic structure that sequesters proteasome core protease (CP) and regulatory particle (RP) complexes into dot-like aggregates when cells become quiescent. This reversible assembly allows cells to store functional proteasomes during periods of reduced metabolic activity and to rapidly redeploy them upon return to growth-permissive conditions. PSGs are distinct from other proteasome-containing structures and represent a key node in proteasome homeostasis. Understanding PSG biology is important because proteasome availability influences protein quality control, stress responses, and cell survival across eukaryotes. Researchers studying quiescence, aging, and proteostasis increasingly rely on PSG markers and genetic models to dissect how cells balance proteasome storage and degradation.
proteasome storage granule At A Glance
| GO ID | GO:0034515 |
|---|---|
| GO term | proteasome storage granule |
| Ontology | cellular_component |
| Synonym | PSG |
| Major function | Storage and protection of proteasome CP and RP complexes during quiescence |
| Cellular location | Cytoplasm, dot-like structures |
| Formation trigger | Quiescence, carbon starvation, acetic acid, nutrient limitation |
| Reversibility | Reversible; proteasomes are released upon growth resumption |
| Related processes | Proteasome homeostasis, microautophagy, nuclear transport |
What Is GO:0034515?
GO:0034515 proteasome storage granule is defined as an aggregation of proteasome core protease (CP) and regulatory particle (RP) complexes that localizes in the cytoplasm as dot-like structures when cells are in a quiescent state. These granules are not membrane-bound organelles but rather dynamic, reversible assemblies that concentrate proteasomes and protect them from autophagic clearance. PSGs are observed in yeast and other eukaryotes and are regulated by nutrient status, mitochondrial respiration, and kinase signaling.
Why Is proteasome storage granule Important in Cell Biology?
PSGs are important because they provide a reversible storage mechanism for proteasomes, which are essential for protein degradation and cellular stress responses. By protecting proteasomes from autophagic degradation during carbon starvation, PSGs help cells survive quiescent periods and rapidly resume growth when nutrients become available. Dysregulation of proteasome storage and availability has been linked to aging, neurodegeneration, and cancer, making PSG biology a relevant area for therapeutic research.
• PSGs protect proteasomes from autophagic degradation during carbon starvation.
• PSG formation is regulated by mitochondrial respiration and kinase signaling.
• PSGs are a hallmark of quiescent cells and are reversible upon growth resumption.
• Proteasome homeostasis involves microautophagy and PSG dynamics.
• Nuclear transport of proteasomes is coordinated with PSG formation.
• Acetic acid induces PSG formation and inhibits proteasomal proteolysis.
• PSG research informs understanding of aging and proteostasis.
• PSGs are conserved from yeast to higher eukaryotes.
• PSG markers are used to study quiescence and dormancy in cell models.
• PSG dysregulation may contribute to proteasome-related diseases.
What Happens During proteasome storage granule?
Initiation of PSG formation
In simple terms: When cells run out of nutrients, proteasomes start clumping together in the cytoplasm.
PSG formation is initiated when cells enter quiescence due to nutrient limitation, carbon starvation, or acetic acid exposure. During this stage, proteasome core protease (CP) and regulatory particle (RP) complexes begin to aggregate into dot-like structures in the cytoplasm. Mitochondrial respiration and kinase signaling pathways are required for efficient PSG assembly.
Maturation and protection
In simple terms: The clumps become stable storage granules that shield proteasomes from being eaten by the cell.
As PSGs mature, they protect proteasomes from autophagic degradation, ensuring that functional proteasomes are preserved during starvation. This protection is critical for maintaining proteasome homeostasis and involves microautophagy regulation. The granules remain dynamic and can be disassembled when conditions improve.
Disassembly and reactivation
In simple terms: When food returns, the granules break apart and proteasomes go back to work.
Upon return to growth-permissive conditions, PSGs disassemble and proteasomes are released to resume proteolytic functions. This reversibility allows cells to rapidly adapt to changing environments. Nuclear transport of proteasomes may also be coordinated with PSG disassembly.
Regulation by metabolic signals
In simple terms: The cell's energy status and signaling pathways control when granules form and fall apart.
PSG formation is regulated through mitochondrial respiration and kinase signaling, linking proteasome storage to cellular metabolic state. Acetic acid and other stress conditions can also induce PSG formation and inhibit proteasomal proteolysis. These regulatory inputs ensure that proteasome storage is tightly coupled to quiescence.
Key Genes Involved in GO:0034515 proteasome storage granule
The following genes and proteins are experimentally implicated in proteasome storage granule biology, based on published literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| PRE1 | Proteasome core protease subunit | Marker for PSG formation and proteasome storage |
| PRE2 | Proteasome core protease subunit | Used to visualize PSG dynamics |
| RPT1 | Proteasome regulatory particle subunit | Required for PSG assembly |
| RPT2 | Proteasome regulatory particle subunit | Involved in PSG formation |
| RPN1 | Proteasome regulatory particle subunit | PSG component and marker |
| RPN2 | Proteasome regulatory particle subunit | PSG assembly and stability |
| BLM10 | Proteasome activator | Regulates proteasome storage |
| ATG1 | Autophagy-related kinase | Links PSG protection to autophagy |
| ATG8 | Autophagosome marker | Used to study PSG protection from autophagy |
| VPS27 | Endosomal sorting | Microautophagy regulation of proteasomes |
| TOR1 | Kinase signaling | Regulates PSG formation via nutrient signaling |
| SCH9 | Kinase signaling | Downstream of TOR in PSG regulation |
| PKA1 | Protein kinase A | Modulates PSG assembly |
| HSP42 | Small heat shock protein | Chaperone involved in granule formation |
| SIS1 | Hsp40 chaperone | Assists proteasome aggregation |
| UBP3 | Ubiquitin protease | Regulates proteasome homeostasis |
| BRE5 | Ubiquitin protease cofactor | Linked to PSG dynamics |
How Is proteasome storage granule Regulated?
PSG formation is regulated by nutrient-sensing pathways, including TOR and PKA signaling, as well as by mitochondrial respiration. Carbon starvation and acetic acid exposure are potent inducers of PSG assembly and inhibitors of proteasomal proteolysis. Microautophagy and nuclear transport pathways also modulate proteasome storage and release.
proteasome storage granule and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| PRE1 | Proteasome dysfunction in neurodegeneration | Knockout yeast or human cell lines |
| RPT1 | Cancer proteasome dependency | Point mutation models |
| ATG1 | Autophagy-related proteostasis | Knockout and overexpression |
| TOR1 | Metabolic regulation of proteostasis | Kinase-dead knock-in |
| BLM10 | Proteasome storage and aging | Tagged knock-in for imaging |
PSGs and neurodegeneration
Proteasome dysfunction is a hallmark of neurodegenerative diseases, and PSG-mediated proteasome storage may influence neuronal survival during stress. Understanding PSG regulation could reveal new targets for protecting proteasomes in aging neurons.
PSGs and cancer
Cancer cells often rely on proteasome activity for survival, and PSG dynamics may affect proteasome availability during metabolic stress. Targeting proteasome storage pathways could complement existing proteasome inhibitors.
PSGs and aging
Quiescent cells, including aged stem cells, utilize PSGs to preserve proteasomes, and decline in this storage capacity may contribute to aging phenotypes.
From proteasome storage granule-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does gene X regulate PSG formation? | Knockout cell line with PSG marker |
| How does point mutation affect PSG assembly? | Point-mutation knock-in |
| Where does protein X localize during quiescence? | Tagged knock-in (fluorescent) |
| Does overexpression of gene Y alter PSG dynamics? | Overexpression cell line |
| Which genes are essential for PSG protection? | CRISPR library screening |
| What is the transcriptomic signature of PSG cells? | RNA-seq of sorted quiescent cells |
How to Study the proteasome storage granule Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Live-cell fluorescence microscopy | PSG formation and disassembly | Tracking granule dynamics |
| Mass spectrometry proteomics | Protein composition of PSGs | Identifying novel PSG components |
| CRISPR knockout screening | Genes required for PSG formation | Functional genomics |
| RNA-seq | Transcriptional changes during quiescence | Identifying regulatory pathways |
| Western blot | Proteasome subunit levels | Validating PSG markers |
| Autophagy flux assays | Protection of proteasomes from degradation | Studying PSG function |
| Kinase inhibitor profiling | Signaling pathways regulating PSGs | Dissecting regulatory inputs |
Live-cell imaging of PSGs
Fluorescently tagged proteasome subunits (e.g., PRE1-GFP) allow real-time visualization of PSG formation and disassembly in live cells. This method is essential for tracking granule dynamics under different nutrient conditions.
Proteomics of PSG fractions
Mass spectrometry-based proteomics can identify proteins enriched in PSG fractions, revealing new components and regulators. This approach helps define the molecular composition of PSGs.
Genetic screens for PSG regulators
CRISPR knockout or overexpression screens can systematically identify genes that affect PSG formation or stability. Such screens link PSG biology to broader cellular pathways.
Transcriptomics of quiescent cells
RNA-seq of cells entering quiescence can reveal transcriptional programs that correlate with PSG formation. This method helps identify upstream regulators of proteasome storage.
How CRISPR Can Be Used to Study GO:0034515 proteasome storage granule
Knockout
CRISPR knockout of candidate genes (e.g., RPT1, ATG1) can test their requirement for PSG formation and proteasome protection. Knockout cell lines with fluorescent PSG markers enable quantitative imaging of granule assembly.
Point Mutation
Point mutations in proteasome subunits or regulatory kinases can dissect specific residues required for PSG assembly without abolishing protein expression. Such models help distinguish catalytic versus structural roles.
Knock-in
Tagged knock-in of proteasome subunits (e.g., PRE1-GFP) allows real-time tracking of PSGs in their native genomic context. This approach preserves endogenous regulation and expression levels.
Overexpression
Overexpression of candidate regulators (e.g., TOR1, BLM10) can test sufficiency for PSG induction or disruption. Overexpression models are useful for gain-of-function studies in quiescent cells.
How EDITGENE Supports proteasome storage granule Research
Researchers studying proteasome storage granule-related genes often need to determine whether a candidate gene is causally involved in PSG formation, protection, or disassembly. EDITGENE provides CRISPR-based cell models and screening services to accelerate this research.
Contact EDITGENE today to design your custom CRISPR model for proteasome storage granule research.
Frequently Asked Questions About proteasome storage granule
What is a proteasome storage granule?
A proteasome storage granule (PSG) is a cytoplasmic aggregation of proteasome core protease and regulatory particle complexes that forms when cells are quiescent.
What is GO:0034515?
GO:0034515 is the Gene Ontology identifier for proteasome storage granule, a cellular component.
What genes are involved in proteasome storage granule formation?
Genes encoding proteasome subunits (PRE1, RPT1), autophagy regulators (ATG1), and signaling kinases (TOR1) are involved.
How are proteasome storage granules regulated?
They are regulated by nutrient signaling, mitochondrial respiration, and kinase pathways such as TOR and PKA.
Why do cells form proteasome storage granules?
Cells form PSGs to protect proteasomes from autophagic degradation during starvation and quiescence.
Are proteasome storage granules reversible?
Yes, PSGs disassemble when cells return to growth-permissive conditions, releasing functional proteasomes.
What methods are used to study proteasome storage granules?
Live-cell imaging, proteomics, CRISPR screens, and RNA-seq are commonly used.
Do proteasome storage granules exist in human cells?
PSG-like structures have been observed in eukaryotic cells, including yeast and higher organisms.
How does acetic acid affect proteasome storage granules?
Acetic acid induces PSG formation and inhibits proteasomal proteolysis.
What diseases are linked to proteasome storage granules?
PSG dysfunction may contribute to neurodegeneration, cancer, and aging-related proteostasis decline.
Conclusion
Proteasome storage granules (GO:0034515) are dynamic cytoplasmic assemblies that protect proteasomes during quiescence and enable rapid reactivation upon growth resumption. Their regulation by nutrient signaling and mitochondrial respiration highlights their integration with cellular metabolism. Continued research using CRISPR models and advanced imaging will further clarify how PSGs contribute to proteostasis in health and disease.
References
- 1. Enenkel C. 2018. The paradox of proteasome granules.. Curr Genet 64(1):137-140 PMID: 28835998
- 2. Li J et al.. 2020. Microautophagy regulates proteasome homeostasis.. Curr Genet 66(4):683-687 PMID: 32077993
- 3. Tang X et al.. 2026. Metabolically regulated proteasome supramolecular organization in situ.. Cell 189(4):1153-1169.e16 PMID: 41605212
- 4. Waite KA et al.. 2022. Proteasome granule formation is regulated through mitochondrial respiration and kinase signaling.. J Cell Sci 135(17) PMID: 35975718
- 5. Wendler P et al.. 2019. Nuclear Transport of Yeast Proteasomes.. Front Mol Biosci 6:34 PMID: 31157235
- 6. Yedidi RS et al.. 2016. Proteasome dynamics between proliferation and quiescence stages of Saccharomyces cerevisiae.. Crit Rev Biochem Mol Biol 51(6):497-512 PMID: 27677933
- 7. Marshall RS et al.. 2018. Proteasome storage granules protect proteasomes from autophagic degradation upon carbon starvation.. Elife 7 PMID: 29624167
- 8. Imajo M et al.. 2026. Acetic acid induces proteasome storage granule formation and inhibits proteasomal proteolysis: Comparison with other induction conditions.. J Biol Chem 302(4):111297 PMID: 41708006
