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. Recent work also links Sqt1 to chaperone-directed repair of oxidatively damaged ribosomes, but the core GO annotations remain Rpl10 carrier chaperone activity, cytosolic localization, and large ribosomal subunit assembly/biogenesis.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005515 protein binding | IPI PMID:16429126 Proteome survey reveals modularity of the yeast cell machine... | MARK AS OVER ANNOTATED | 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 GO:0140597 protein carrier chaperone, supported directly by PMID:26112308. 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... | MARK AS OVER ANNOTATED | 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: Retaining generic protein binding would obscure the curated function: Sqt1 binds Rpl10 as a dedicated ribosomal-protein chaperone during 60S subunit maturation. 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 ... | MARK AS OVER ANNOTATED | 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. SQT1 should be curated around experimentally supported Rpl10 carrier chaperone activity and 60S subunit assembly rather than generic protein binding. Supporting Evidence: file:yeast/SQT1/SQT1-deep-research-falcon.md Sqt1 is not an enzyme catalyzing a chemical transformation; instead, it is best described as a protein-folding/handling factor that binds Rpl10 and supports its productive assembly into late pre-60S particles. |
| GO:0005515 protein binding | IPI PMID:37968396 The social and structural architecture of the yeast protein ... | MARK AS OVER ANNOTATED | Summary: A large-scale interactome protein binding annotation is less informative than the mechanistic Sqt1-Rpl10 chaperone model. Reason: Generic protein binding should not be accepted as a core molecular function when a specific carrier chaperone activity for Rpl10 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. |
Loading supporting contentβ¦
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
Loading supporting contentβ¦
Download this section (compressed HTML)Loading supporting contentβ¦
Download this section (compressed HTML)