UniProt ID: Q01477
Organism: Saccharomyces cerevisiae
EC Number: 3.4.19.12
Total Annotations Reviewed: 54
| Action | Count | Percentage |
|---|---|---|
| ACCEPT | 33 | 61.1% |
| REMOVE | 10 | 18.5% |
| MARK_AS_OVER_ANNOTATED | 2 | 3.7% |
| MODIFY | 1 | 1.9% |
| KEEP_AS_NON_CORE | 1 | 1.9% |
| PENDING | 7 | 13.0% |
Core Catalytic Functions (ACCEPT):
- Cysteine-type deubiquitinase activity: 4 annotations (IBA, IEA, IMP, IDA)
- Protein deubiquitination: 6 annotations (IEA, IMP, IMP, IDA, IMP, IMP)
- Total core catalytic: 10 annotations
Biological Processes Supporting Core Function (ACCEPT):
- Ribophagy: 3 annotations (NAS, IMP, IMP)
- Stress granule assembly: 1 annotation (IDA)
- ER-Golgi transport regulation: 3 annotations (NAS, IMP, IMP)
- Retrograde transport: 1 annotation (NAS)
- Golgi protein retention: 6 annotations (4x IMP, 2x IGI)
- Osmotic stress response: 2 annotations (IMP, IPI)
- Total processes: 16 annotations
Localization Terms (ACCEPT):
- Nucleus: 1 annotation (IBA)
- Cytoplasm: 1 annotation (IDA)
- Cytosol: 3 annotations (IBA, IDA, HDA)
- Mitochondrion: 1 annotation (IDA - dynamic)
- Ubp3-Bre5 complex: 1 annotation (IPI)
- Total localization/complex: 7 annotations
Molecular Function - General Terms (ACCEPT):
- Hydrolase activity: 1 annotation (IEA)
- Peptidase activity: 1 annotation (IEA)
- Cysteine-type peptidase activity: 1 annotation (IEA)
- Total general function: 3 annotations
Problematic Annotations (REMOVE/MODIFY):
- Protein binding (generic): 8 annotations - ALL REMOVE
- mRNA binding: 2 annotations - MARK_AS_OVER_ANNOTATED
- Regulation of protein stability: 1 annotation - REMOVE
- Proteolysis (overly general): 1 annotation - MODIFY
All four annotations of GO:0004843 (cysteine-type deubiquitinase activity) are ACCEPTED:
- IBA: Phylogenetic inference based on conserved catalytic domain (C19 family, IPR001394)
- IEA: InterPro domain-based inference with EC classification (3.4.19.12)
- IMP: Experimental evidence showing catalytic activity required for MAPK signaling function
- IDA: Original biochemical characterization by Baker et al. (1992)
Rationale: This is the core molecular function of UBP3. Multiple independent evidence types all converge on the same conclusion. The enzyme family assignment is well-established, crystal structures are available, and catalytic activity is demonstrated biochemically in multiple substrates.
All six annotations of GO:0016579 (protein deubiquitination) are ACCEPTED:
- IEA: InterPro domain-based inference (appropriate for USP family)
- IMP (Ste7): Genetic evidence that catalytic activity regulates MAPK pathway
- IMP (Ste7 alternate): Complementary experimental approach
- IDA (RNAP II): Direct biochemical analysis of RNA polymerase II substrate
- IMP (RNAP II): Functional requirement for RNAP II deubiquitination
- IMP (Ras/cAMP): Functional analysis of signaling pathway regulation
Rationale: Deubiquitination is the fundamental biological process catalyzed by UBP3. Evidence is robust across multiple substrates (RNAP II, Ste7, general protein substrates). Each annotation documents a specific substrate or functional context.
All three annotations of GO:0034517 (ribophagy) are ACCEPTED:
- NAS: Named assertion based on discovery of ribophagy pathway dependent on Ubp3
- IMP: Genetic knockout shows accumulation of 60S ribosomes under starvation
- IMP (CDC48/UFD3): Functional analysis identifying complex cofactors required
Rationale: Ribophagy is a well-established selective autophagy pathway discovered in the referenced study. UBP3 catalytic activity is essential. This is a core biological role, particularly important for nutrient starvation response and cell survival.
GO:0034063 (stress granule assembly) - ACCEPT (IDA)
Rationale: IDA evidence from targeted genetic screen demonstrates UBP3 catalytic activity is specifically required for stress granule formation. This function is unique among UBP family members and requires both catalytic activity and Bre5 cofactor. Stress granules are important for cell survival in stationary phase.
All annotations related to ER-Golgi transport are ACCEPTED:
- GO:0060628 (ER to Golgi transport) - NAS and IMP
- GO:2000156 (retrograde Golgi to ER transport) - NAS
- GO:0045053 (Golgi protein retention) - 4x IMP, 2x IGI
Rationale: These transport processes are mechanistically linked through SEC23 deubiquitination. UBP3-Bre5 complex removes ubiquitin from SEC23, maintaining protein levels necessary for COPII coat function. The recent discovery of a novel mechanism for Golgi protein retention (via Ubp3-Bre5 deubiquitination) warrants acceptance of all transport-related terms.
GO:0047484 (regulation of response to osmotic stress) - IMP and IPI
Rationale: UBP3 activity is directly modulated by Hog1 MAPK kinase under osmotic stress (phosphorylation-mediated activation). This couples osmotic stress sensing to deubiquitination pathway regulation. Both IMP and IPI evidence establish functional relationship.
All localization annotations are ACCEPTED:
- Nucleus (IBA): Supporting evidence from RNAP II and histone deubiquitination substrates
- Cytoplasm (IDA): Direct detection from cellular fractionation
- Cytosol (IBA, IDA, HDA): Multiple confirmations of major catalytic compartment
- Mitochondrion (IDA): Dynamic translocation during mitophagy induction
Rationale: Localization is consistent with known substrate distribution and functional requirements. Notably, mitochondrial localization is stimulus-dependent (upon mitophagy induction), which is informative about regulatory mechanism.
GO:1990861 (Ubp3-Bre5 deubiquitination complex) - ACCEPT (IPI)
Rationale: This is a well-characterized complex with available crystal structure (PDB:2QIY). Direct physical interaction is documented. This is not generic protein binding but a named functional complex with defined stoichiometry (heterotetrameric, 2:2 Ubp3:Bre5).
Three parent terms (hydrolase, peptidase, cysteine-type peptidase activity) are ACCEPTED:
Rationale: These are appropriate parent terms in the catalytic hierarchy. The specific cysteine-type deubiquitinase activity is most informative, but these parent terms provide useful categorical information in the GO hierarchy.
ALL INSTANCES REMOVED
Evidence sources:
- PMID:16429126, PMID:16554755 (2x variants), PMID:17632125, PMID:18719252, PMID:20508643, PMID:21179020, PMID:37968396
Rationale:
1. Overly generic: Protein binding does not distinguish between functional substrates, regulatory proteins, and non-specific interactions
2. Violates GO best practices: GO curation guidelines recommend avoiding protein binding in favor of more specific molecular function terms
3. More specific terms available:
- BRE5 interaction → GO:1990861 (Ubp3-Bre5 complex membership) is far more informative
- Other interactions not functionally characterized → should not be annotated
4. Confuses mechanism with function: Catalytic activity (GO:0004843) is the relevant molecular function, not passive substrate binding
5. Not substrate-specific: These annotations represent binary interactions from databases without mechanistic characterization
Implementation: Replace all protein binding annotations with more specific terms where available (complex membership for Bre5) or remove entirely where no functional characterization exists.
REMOVE (IBA)
Rationale:
1. Indirect consequence, not direct function: Protein stability regulation is a downstream effect of removing ubiquitin degradation signals, not the direct catalytic function
2. Too broad: Applies to any deubiquitinase and does not capture substrate specificity
3. Redundant with specific annotations: The substrate-specific deubiquitination terms (SEC23, RNAP II, Ste7, ribophagy targets) are far more informative
4. Misleading specificity level: Suggests broader function than actually characterized
Implementation: Remove in favor of substrate-specific process annotations.
MODIFY (IEA from GO_REF:0000043)
Current status: IEA from UniProtKB keyword "Protease"
Rationale:
1. Overly general: Proteolysis encompasses all protein-cleaving activities, inappropriate for specialized deubiquitinase
2. Loses specificity: Ubiquitin C-terminal hydrolysis is a specific type of proteolysis with distinct mechanism and substrates
3. Redundant information: If annotated, this is implied by more specific catalytic terms already present
4. Not recommended in current literature: GO curators increasingly avoid this broad term in favor of specific enzyme family roles
Implementation: Remove this annotation or modify to more specific hydrolysis term if available (e.g., ubiquitin carboxyl-terminal hydrolysis, if defined).
Both marked as OVER_ANNOTATED
Evidence:
- HDA: PMID:23222640 (yeast mRNP proteome survey)
- IDA: PMID:20844764 (proteome-wide RNA-binding protein survey)
Rationale:
1. Limited mechanistic evidence: These are proteome-wide surveys that identify proteins co-fractionating with mRNPs/RNA
2. Confuses localization with function: Presence in stress granules (RNA-rich compartment) does not demonstrate functional mRNA binding
3. Catalytic activity is demonstrated mechanism: The functional requirement in stress granules is UBP3 CATALYTIC ACTIVITY (deubiquitination), not mRNA interaction
4. No substrate specificity documented: If UBP3 does bind RNA, the specific mRNA targets and biological role are uncharacterized
5. Better captured by process terms: GO:0034063 (stress granule assembly) already captures Ubp3's role in this RNA-containing structure
Interpretation: While UBP3 may localize to and transiently associate with mRNAs in stress granules, the biological role appears to be deubiquitination of granule component proteins, not mRNA binding per se. The annotation is not false but represents an inference that may not capture the true mechanism.
Keep as NON-CORE (IMP, PMID:25704822)
Rationale:
1. Well-supported experimentally: The evidence is strong (genome-wide screen, direct functional testing)
2. However, not primary function: Ubp3 PROMOTES ribophagy while INHIBITING mitophagy - selective pathway regulation
3. Specialized regulatory role: While important, negative mitophagy regulation is not a core catalytic function like ribophagy
4. Maintains pathway context: Keeping this annotation shows the complex reciprocal regulation of different autophagy pathways by the same deubiquitinase
5. Secondary/pleiotropic: For a pleiotropic gene with multiple functions, designating some as "non-core" appropriately reflects relative functional importance
Interpretation: This annotation should be retained to capture the full biological picture, but flagged as non-core to indicate that UBP3's primary roles are positive activation of ribophagy and substrate-specific deubiquitination, rather than negative regulation of other pathways.
Several annotations remain PENDING pending access to original publications that have not yet been retrieved:
These will be finalized once all publications are obtained.
Strongest possible evidence for molecular mechanism
IMP + Genetic Analysis (PMID:18391941, PMID:26503781)
Functional importance demonstrated in vivo
IDA + Biochemistry (PMID:1429680)
Often strongest for ubiquitin-processing enzymes (highly conserved)
IMP - Functional mutation analysis
Should not be sole evidence for specific functional claims
HDA/IDA from proteome-wide surveys - High-throughput methods
Appropriate for localization but not substrate specificity
IPI from binary interaction databases - Interaction detection
Often needs supporting functional evidence
NAS - Named assertion
Based on literature review, the following substrate-specific functions are well-supported but not currently in the annotation set:
Status: Consider adding if substrate mechanism is further characterized in literature
Transcriptional Regulation
Status: Well-supported through RNAP II deubiquitination; may warrant explicit annotation
mRNA Decay and Ribosomal Protein Turnover
Do not add new annotations for these functions unless:
1. Direct substrate evidence explicitly documented in literature
2. GO terms are appropriate and specific
3. Evidence codes are clear and retrievable
4. Multiple independent sources confirm functional importance
Current annotation set captures essential functions well.
Catalytic activity prioritized: The direct molecular function (deubiquitination) takes precedence over indirect consequences (protein stability)
Specificity over generality: Preferred specific substrate pathways (ribophagy, SEC23 deubiquitination) over generic terms (proteolysis, protein binding)
Cofactor relationships documented: Complex membership (GO:1990861) preferred for BRE5 interaction over generic binding
Localization matched to function: Accepted nuclear localization based on RNAP II substrate; mitochondrial localization appropriate for mitophagy regulation
Evidence quality matters: IDA/IMP with functional characterization weighted more heavily than IEA keyword mapping
Conflict: Multiple evidence types for GO:0004843
- Resolution: All accepted; multiple evidence types strengthen confidence. Different codes document different aspects (biochemical activity, evolutionary conservation, functional requirement)
Conflict: Generic vs. specific protein interaction
- Resolution: Generic "protein binding" removed; specific complex/pathway terms retained. Complex membership (GO:1990861) is far more informative than binary interaction
Conflict: mRNA localization vs. catalytic requirement
- Resolution: Marked as over-annotated, not false. Localization is real but mechanism is deubiquitination (GO:0034063 stress granule assembly), not mRNA binding
Incomplete literature access: Some PMID sources not yet retrieved. Could affect final curation of 7 pending annotations
Substrate specificity evolution: As more substrates are discovered, additional substrate-specific process annotations may become appropriate
Histone modifications: H2B K123 deubiquitination mentioned in UniProt but not explicitly in current GO annotations. May warrant future addition with proper sourcing
Conditional localization: Mitochondrial localization is stimulus-dependent. Current annotation captures this accurately as IDA with supporting reference
UBP3 is fundamentally a well-characterized deubiquitinase with clear molecular function (GO:0004843) and multiple important biological roles (ribophagy, transcriptional regulation, stress response). The current annotation set has significant redundancy (8 generic protein binding terms) and some overly indirect terms (regulation of protein stability), but the core functional annotations are appropriate and well-supported.
After curation:
- Accept: 33 annotations capturing core catalytic and selective biological functions
- Remove: 10 annotations that are generic, redundant, or overly indirect
- Over-annotated: 2 mRNA binding terms that reflect co-localization rather than functional mechanism
- Non-core: 1 mitophagy regulation annotation that is secondary to primary ribophagy function
The resulting annotation set provides a clear, specific, and mechanistically grounded representation of UBP3 function in yeast protein quality control, selective autophagy, and transcriptional regulation.