SQT1 encodes an essential cytosolic WD40 beta-propeller protein that functions as the dedicated carrier chaperone for ribosomal protein Rpl10/uL16. Sqt1 binds the highly basic N-terminus of nascent Rpl10, shields the rRNA-binding surface, prevents nonspecific interactions or aggregation, and supports late cytoplasmic loading of Rpl10 into pre-60S ribosomal subunits. The older QSR1 suppression phenotype and half-mer polysome defects are therefore best interpreted through this late 60S assembly/Rpl10 handling function. The same Rpl10-handling activity also enables chaperone-directed repair of oxidatively damaged mature ribosomes by releasing oxidized Rpl10 for replacement.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005515 protein binding | IPI PMID:16429126 Proteome survey reveals modularity of the yeast cell machine... | REMOVE | Summary: Protein binding is true but too generic for Sqt1. The biologically informative interaction is client-specific binding to Rpl10 as a dedicated ribosomal-protein carrier chaperone. Reason: GO:0005515 does not capture the direction, specificity, or functional consequence of Sqt1-Rpl10 binding. The core molecular function is better represented by the existing GO:0051082 replacement, GO:0140597 protein carrier chaperone; the generic binding assertion should not be retained as a separate molecular-function annotation. Supporting Evidence: PMID:26112308 Affinity purification of four chaperones (Rrb1, Syo1, Sqt1 and Yar1) selectively enriched the mRNAs encoding their specific ribosomal protein clients (Rpl3, Rpl5, Rpl10 and Rps3). |
| GO:0005515 protein binding | IPI PMID:16554755 Global landscape of protein complexes in the yeast Saccharom... | REMOVE | Summary: High-throughput complex data support physical association, but GO:0005515 is a vague annotation that does not express Sqt1's specific Rpl10 carrier chaperone function. Reason: The reported physical association is consistent with the Sqt1-Rpl10 chaperone model, but GO:0005515 is uninformative once a direct client-specific chaperone activity is curated. This generic binding row should be removed rather than retained as a non-core function. Supporting Evidence: PMID:26112308 X-ray crystallography reveals how the N-terminal, rRNA-binding residues of Rpl10 are shielded by Sqt1's WD-repeat beta-propeller, providing mechanistic insight into the incorporation of Rpl10 into pre-60S subunits. |
| GO:0005515 protein binding | IPI PMID:27107014 An inter-species protein-protein interaction network across ... | REMOVE | Summary: Inter-species high-throughput protein binding observations are not a good basis for a yeast SQT1 core function annotation. Reason: The reported cross-species interactors do not define Sqt1's yeast cellular role or justify a generic GO molecular-function annotation. SQT1 should be curated around experimentally supported Rpl10 carrier chaperone activity and 60S subunit assembly rather than GO:0005515. Supporting Evidence: PMID:27107014 An inter-species protein-protein interaction network across vast evolutionary distance. |
| GO:0005515 protein binding | IPI PMID:37968396 The social and structural architecture of the yeast protein ... | REMOVE | Summary: A large-scale interactome protein binding annotation is less informative than the mechanistic Sqt1-Rpl10 chaperone model. Reason: The large-scale interaction recovers the known Sqt1-Rpl10 association, but generic protein binding should not be accepted as a molecular function when a specific Rpl10 carrier chaperone activity is supported by biochemical and structural evidence. Supporting Evidence: PMID:26112308 Co-translational capturing of nascent ribosomal proteins by dedicated chaperones constitutes an elegant mechanism to prevent unspecific interactions and aggregation of ribosomal proteins on their road to incorporation. |
| GO:0051082 unfolded protein binding | IDA PMID:26112308 Co-translational capturing of nascent ribosomal proteins by ... | MODIFY | Summary: The evidence from PMID:26112308 supports a dedicated Rpl10 carrier chaperone activity, not generic binding to unfolded proteins. Reason: Sqt1 binds the Rpl10 N-terminus with client specificity and shields aggregation-prone rRNA-binding residues before Rpl10 incorporation into pre-60S subunits. GO:0140597 protein carrier chaperone is the appropriate replacement. Proposed replacements: protein carrier chaperone Supporting Evidence: PMID:26112308 X-ray crystallography reveals how the N-terminal, rRNA-binding residues of Rpl10 are shielded by Sqt1's WD-repeat beta-propeller, providing mechanistic insight into the incorporation of Rpl10 into pre-60S subunits. |
| GO:0005737 cytoplasm | HDA PMID:11914276 Subcellular localization of the yeast proteome | ACCEPT | Summary: Cytoplasmic localization is consistent with Sqt1's role in co-translational Rpl10 capture and late cytoplasmic 60S maturation. Reason: The high-throughput cytoplasm annotation agrees with the mechanistic model and with the more specific cytosol annotation. Supporting Evidence: file:yeast/SQT1/SQT1-deep-research-falcon.md The combined evidence supports Sqt1 acting primarily in the cytoplasm, where late 60S maturation steps occur, including Rpl10 loading and Nmd3 release coordinated with Lsg1. |
| GO:0042273 ribosomal large subunit biogenesis | IMP PMID:26112308 Co-translational capturing of nascent ribosomal proteins by ... | ACCEPT | Summary: Sqt1 is a dedicated Rpl10 chaperone required for proper late 60S ribosomal subunit maturation. Reason: This process annotation accurately captures Sqt1's role in ribosomal large subunit biogenesis through client-specific Rpl10 handling. Supporting Evidence: PMID:26112308 X-ray crystallography reveals how the N-terminal, rRNA-binding residues of Rpl10 are shielded by Sqt1's WD-repeat Ξ²-propeller, providing mechanistic insight into the incorporation of Rpl10 into pre-60S subunits. |
| GO:0000027 ribosomal large subunit assembly | IMP PMID:9271392 SQT1, which encodes an essential WD domain protein of Saccha... | ACCEPT | Summary: The original SQT1 study showed half-mer polysome defects and reduced Qsr1 levels on free 60S subunits when SQT1 function was reduced, supporting a late 60S assembly function. Reason: This annotation remains correct and is strengthened by later evidence that Sqt1 chaperones Rpl10 for late pre-60S incorporation. Supporting Evidence: PMID:9271392 Loss of SQT1 function by down regulation from an inducible promoter results in formation of half-mer polyribosomes and decreased Qsr1p levels on free 60S subunits. Sqt1p thus appears to be involved in a late step of 60S subunit assembly or modification in the cytoplasm. |
| GO:0005829 cytosol | IDA PMID:9271392 SQT1, which encodes an essential WD domain protein of Saccha... | ACCEPT | Summary: Cytosolic localization is consistent with the original biochemical fractionation and with Sqt1's role in co-translational Rpl10 capture and late cytoplasmic 60S maturation. Reason: Cytosol is the best-supported core cellular location for Sqt1 function. Supporting Evidence: PMID:9271392 Sqt1p thus appears to be involved in a late step of 60S subunit assembly or modification in the cytoplasm. |
| GO:0034599 cellular response to oxidative stress | IMP PMID:37086725 Chaperone-directed ribosome repair after oxidative damage. | NEW | Summary: Sqt1-dependent release of oxidized Rpl10 from mature ribosomes supports ribosome repair during oxidative stress. Reason: Yang et al. directly connected Sqt1 to the cellular oxidative-stress response: purified Sqt1 released oxidized Rpl10 from mature 60S subunits, Sqt1 was recruited to ribosomes in hydrogen peroxide-treated yeast, and an Sqt1 interface mutant that cannot bind Rpl10 retained an oxidative-stress growth defect even when supplied with excess Rpl10. GO:0034599 is justified as a non-core process annotation because Sqt1 performs the Rpl10 extraction step in this repair route rather than merely being required for downstream stress resistance. Supporting Evidence: PMID:37086725 Oxidized Rps26 and Rpl10 are released from ribosomes by their chaperones, Tsr2 and Sqt1, and the damaged ribosomes are subsequently repaired with newly made proteins. |
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Download this section (compressed HTML)Q: Which handoff factors receive Rpl10 from Sqt1 during Lsg1- and Nmd3-linked late 60S maturation?
Q: How much of Sqt1's essential growth role reflects co-translational Rpl10 capture versus later ribosome repair of damaged Rpl10?
Q: Are non-Rpl10 high-throughput Sqt1 interactors reproducible functional partners, contaminants, or context-specific stress interactions?
Experiment: Use separation-of-function SQT1 interface mutants to compare Rpl10 binding, Rpl10 solubility, 60S subunit maturation, and oxidative-stress repair in the same strain background.
Type: genetics
Experiment: Reconstitute Sqt1-mediated Rpl10 handoff to pre-60S particles with purified late maturation factors and measure dependence on Lsg1 and Nmd3 remodeling.
Type: biochemistry
Experiment: Validate high-throughput Sqt1 protein-binding partners by reciprocal co-immunoprecipitation and test whether any interactions change under ribosome assembly stress or oxidative stress.
Type: proteomics
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Download this section (compressed HTML)Specific assembly chaperone for ribosomal protein Rpl10p; co-translationally associates with nascent Rpl10p, preventing aggregation; involved in biogenesis of the ribosomal large subunit; contains multiple WD repeats; interacts genetically and physically with Qsr1p; protein abundance increases in response to DNA replication stress
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