SHQ1 encodes an essential conserved chaperone/assembly factor for box H/ACA small nucleolar RNP biogenesis. Shq1 binds the pseudouridine synthase Cbf5, uses an RNA-mimic domain to block premature RNA engagement, and promotes early assembly before handoff to later factors such as Naf1. The best-supported core function is protein chaperoning in box H/ACA snoRNP assembly in the nucleus or nucleoplasm; oxygen-dependent cytosolic relocalization is supported but is not the central conserved function.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0005654 nucleoplasm | IBA GO_REF:0000033 | ACCEPT | Summary: Phylogenetic nucleoplasmic localization is consistent with Shq1's conserved nuclear H/ACA assembly role. Reason: Shq1 acts during early H/ACA snoRNP assembly with nuclear/nucleoplasmic components such as Cbf5. Supporting Evidence: PMID:12228251 required for box H/ACA small nucleolar ribonucleoprotein particle biogenesis file:interpro/panther/PTHR12967/PTHR12967-metadata.yaml PROTEIN SHQ1 HOMOLOG |
| GO:0005737 cytoplasm | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Cytoplasmic localization is supported in some contexts, but it is not the core functional site for H/ACA snoRNP assembly. Reason: Oxygen-dependent localization studies support cytosolic/cytoplasmic pools, while the central conserved function remains nuclear/nucleoplasmic assembly of H/ACA particles. Supporting Evidence: PMID:22932476 over 120 nuclear proteins with important functions ranging from transcriptional regulation to RNA processing exhibit altered cellular locations under hypoxia |
| GO:0000493 box H/ACA snoRNP assembly | IBA GO_REF:0000033 | ACCEPT | Summary: The conserved H/ACA snoRNP assembly annotation is well supported. Reason: Shq1 homologs are Cbf5-associated assembly chaperones required for H/ACA RNP biogenesis. Supporting Evidence: PMID:12228251 required for box H/ACA small nucleolar ribonucleoprotein particle biogenesis file:yeast/SHQ1/SHQ1-deep-research-falcon.md assembly chaperone for box H/ACA |
| GO:0051082 unfolded protein binding | IBA GO_REF:0000033 | MODIFY | Summary: The family transfer captures a chaperone activity, but unfolded protein binding is too broad for Shq1. Reason: Shq1 is a Cbf5-directed chaperone/assembly factor, so protein carrier chaperone is more informative than generic unfolded protein binding. Proposed replacements: protein carrier chaperone Supporting Evidence: PMID:19426738 Shq1p is a chaperone protein ... that binds to the Cbf5p enzyme |
| GO:0000493 box H/ACA snoRNP assembly | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro-derived H/ACA snoRNP assembly is correct. Reason: Shq1 is a conserved H/ACA assembly factor and yeast experiments directly support this process. Supporting Evidence: PMID:12228251 required for box H/ACA small nucleolar ribonucleoprotein particle biogenesis |
| GO:0005634 nucleus | IEA GO_REF:0000044 | ACCEPT | Summary: Nuclear localization is supported and relevant to H/ACA snoRNP assembly. Reason: Shq1 acts with nuclear/nucleolar H/ACA assembly machinery, although cytosolic localization has also been observed under oxygen-regulated conditions. Supporting Evidence: PMID:12228251 small nucleolar ribonucleoprotein particle biogenesis |
| GO:0005829 cytosol | IDA PMID:22932476 The nuclear localization of SWI/SNF proteins is subjected to... | KEEP AS NON CORE | Summary: Cytosolic localization is experimentally observed, but should be treated as non-core relative to the H/ACA assembly role. Reason: The oxygen-regulation study supports localization dynamics; it does not redefine the primary conserved molecular function. Supporting Evidence: PMID:22932476 over 120 nuclear proteins with important functions ranging from transcriptional regulation to RNA processing exhibit altered cellular locations under hypoxia |
| GO:0000493 box H/ACA snoRNP assembly | IMP PMID:12228251 The Shq1p.Naf1p complex is required for box H/ACA small nucl... | ACCEPT | Summary: Mutant/depletion evidence directly supports H/ACA snoRNP assembly. Reason: Shq1 depletion reduces H/ACA snoRNA/RNP accumulation and causes defects in H/ACA particle biogenesis. Supporting Evidence: PMID:12228251 required for box H/ACA small nucleolar ribonucleoprotein particle biogenesis |
| GO:0000493 box H/ACA snoRNP assembly | IPI PMID:12228251 The Shq1p.Naf1p complex is required for box H/ACA small nucl... | ACCEPT | Summary: Interaction evidence with H/ACA assembly factors supports the same assembly process. Reason: Shq1 interaction with Cbf5/Nhp2/Naf1 context is mechanistically tied to early H/ACA snoRNP assembly. Supporting Evidence: PMID:12228251 The Shq1p.Naf1p complex is required |
| GO:0005634 nucleus | IDA PMID:22932476 The nuclear localization of SWI/SNF proteins is subjected to... | ACCEPT | Summary: Nuclear localization is supported and consistent with the core assembly role. Reason: H/ACA snoRNP biogenesis is a nuclear/nucleolar process, and the localization study supports oxygen-regulated nuclear presence. Supporting Evidence: PMID:22932476 over 120 nuclear proteins with important functions ranging from transcriptional regulation to RNA processing exhibit altered cellular locations under hypoxia |
| GO:0005654 nucleoplasm | IDA PMID:12228251 The Shq1p.Naf1p complex is required for box H/ACA small nucl... | ACCEPT | Summary: Nucleoplasmic localization is consistent with early H/ACA assembly. Reason: Shq1 acts on Cbf5 before mature H/ACA RNP formation, making nucleoplasm a defensible functional compartment. Supporting Evidence: PMID:12228251 box H/ACA small nucleolar ribonucleoprotein particle biogenesis |
| GO:0051082 unfolded protein binding | IDA PMID:19426738 The box H/ACA snoRNP assembly factor Shq1p is a chaperone pr... | MODIFY | Summary: The experiment supports chaperone binding to Cbf5, but unfolded protein binding is too generic. Reason: Shq1 is a dedicated H/ACA assembly chaperone for Cbf5 rather than a general unfolded-protein binder. Proposed replacements: protein carrier chaperone Supporting Evidence: PMID:19426738 Shq1p is a chaperone protein ... that binds to the Cbf5p enzyme |
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Download this section (compressed HTML)Q: What triggers release of Cbf5 from Shq1 and handoff to Naf1 or nascent H/ACA RNA during yeast RNP assembly?
Suggested experts: snoRNP assembly experts, RNA-protein complex biochemists
Q: Does the oxygen-dependent cytosolic pool of Shq1 have a regulated assembly function or represent sequestration away from nuclear H/ACA biogenesis?
Suggested experts: yeast stress-response researchers
Experiment: Reconstitute yeast Cbf5-Shq1-Naf1-H/ACA RNA transitions and monitor handoff by fluorescence, EMSA, and activity assays using wild-type and RNA-mimic-domain mutants.
Hypothesis: Shq1 prevents premature Cbf5-RNA engagement until a defined handoff step promotes productive H/ACA RNP assembly.
Type: time-resolved assembly reconstitution
Experiment: Engineer Shq1 mutants or conditional anchors that selectively alter nuclear versus cytosolic localization, then measure H/ACA snoRNA accumulation and pseudouridylation under normoxia and hypoxia.
Hypothesis: Nuclear/nucleoplasmic Shq1 is sufficient for core H/ACA assembly, while cytosolic relocalization modulates availability under oxygen stress.
Type: localization-function separation assay
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