HSC82 encodes the abundant constitutive cytosolic Hsp90 isoform in S. cerevisiae, an ATP-regulated protein folding chaperone that acts through nucleotide binding, conformational cycling, and regulated ATP hydrolysis to mature and stabilize selected client proteins. Hsc82 functions as an Hsp90 dimer and engages co-chaperones such as Sti1, Cpr6/Cpr7, Sba1/p23, Aha1, Cdc37, Sse1, and Sgt1. It is cytosolic under normal growth conditions, contributes to elevated-temperature fitness despite being less heat-inducible than HSP82, and supports client pathways including calcineurin, kinase/signaling clients, telomerase, R2TP/snoRNP, and proteasome assembly. Hsc82 and the stress-inducible Hsp82 paralog have largely overlapping client repertoires but differ in abundance, conformational dynamics, thermal stability, and some client and co-chaperone interactions.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0006457 protein folding | IBA GO_REF:0000033 | ACCEPT | Summary: HSC82/Hsp90 is a well-established protein folding chaperone. IBA annotation is consistent with the known function of this conserved chaperone family across eukaryotes. Reason: Protein folding is a core biological process for Hsp90. UniProt describes HSC82 as an "ATP-dependent molecular chaperone" that promotes maturation and regulation of client proteins. IMP evidence from PMID:7791797 confirms involvement in protein folding. Supporting Evidence: file:yeast/HSC82/HSC82-deep-research-falcon.md Hsp90/Hsc82 functions as an ATP-dependent folding chaperone for late intermediates/clients, and specific Hsp90 mutants that disrupt client loading/closing/reopening cause client-specific maturation defects and temperature-sensitive growth. |
| GO:0016887 ATP hydrolysis activity | IBA GO_REF:0000033 | ACCEPT | Summary: HSC82 has well-characterized ATPase activity essential for its chaperone cycle. IBA annotation is correct. Reason: ATPase activity is fundamental to Hsp90 function. Directly demonstrated by IDA (PMID:18492664). UniProt documents the ATP binding and hydrolysis mechanism. Supporting Evidence: file:yeast/HSC82/HSC82-deep-research-falcon.md N-terminal ATP-binding domain; ATP binding drives lid closure and N-terminal association; Hsc82 shows higher ATPase activity than Hsp82 at 30β37Β°C file:yeast/HSC82/HSC82-deep-research-falcon.md Aha1 and Cpr6 stimulate ATPase activity of both isoforms, while Cdc37, Sba1/p23, and Sti1 inhibit with only minor isoform-specific differences. |
| GO:0032991 protein-containing complex | IBA GO_REF:0000033 | MARK AS OVER ANNOTATED | Summary: HSC82 forms Hsp90 dimers and multiple co-chaperone/client complexes, but the generic protein-containing complex term is not very informative. Reason: Hsc82 participates in many complexes as an Hsp90 chaperone, but GO:0032991 does not identify the biologically meaningful assembly. The evidence is better represented by Hsp90 dimer/co-chaperone/client complex context together with ATP-dependent protein folding chaperone activity. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: GRANULARITY MISMATCH Sources checked: PANTHER:PTN000163629 Β· PAINT Hsp90 family node SUPPORTS TRANSFER Hsp90 proteins genuinely form dimers and client/co-chaperone assemblies, but the propagated protein-containing complex term is too generic to identify any such assembly. Supporting Evidence: file:yeast/HSC82/HSC82-deep-research-falcon.md Hsc82 forms many complexes, but specific complexes (homodimer; Sti1/Cpr6/Sba1/Cdc37/Sgt1 complexes) are more biologically useful than a generic complex term file:yeast/HSC82/HSC82-deep-research-falcon.md Constitutive C-terminal dimerization is central to Hsp90 architecture; nucleotide binding promotes transient N-terminal dimerization during the cycle |
| GO:0005886 plasma membrane | IBA GO_REF:0000033 | MARK AS OVER ANNOTATED | Summary: IBA annotation for plasma membrane localization. HSC82 is primarily cytoplasmic but plasma membrane association has some HDA support (PMID:16622836). Reason: HSC82 is an abundant soluble cytosolic chaperone. Detection in a plasma-membrane proteomics dataset does not establish stable membrane residence, and no targeted localization evidence supports a functional plasma-membrane pool. Propagation Review Root cause: PROPAGATION BAD Failure modes: COMPARTMENT OR COMPLEX MISMATCH Sources checked: PANTHER:PTN000163629 Β· PAINT Hsp90 family node SUPPORTS SOURCE BUT NOT TARGET Plasma-membrane localization may occur for some Hsp90 descendants, but this abundant soluble yeast Hsp90 lacks targeted evidence for stable membrane residence. |
| GO:0005524 ATP binding | IBA GO_REF:0000033 | ACCEPT | Summary: HSC82 binds ATP as part of its chaperone cycle. Well-established by crystallography of Hsp90 orthologs. Reason: ATP binding is essential for Hsp90 function. The N-terminal domain contains the Bergerat ATP-binding fold. UniProt documents the ATP binding site residues. Supporting Evidence: file:yeast/HSC82/HSC82-deep-research-falcon.md N-terminal ATP-binding domain; ATP binding drives lid closure and N-terminal association; Hsc82 shows higher ATPase activity than Hsp82 at 30β37Β°C |
| GO:0005829 cytosol | IBA GO_REF:0000033 | ACCEPT | Summary: HSC82 is a cytosolic protein. IBA annotation is correct. Reason: Consistent with HDA evidence for cytoplasm localization (PMID:14562095). Cytosol is the expected primary localization for Hsp90. Supporting Evidence: file:yeast/HSC82/HSC82-deep-research-falcon.md Hsc82 is described as the constitutive cytosolic Hsp90 isoform; many experimental Hsc82 interactome/purification studies use cytosolic lysates, consistent with CC:cytosol annotations for both isoforms, with expression-level differences for HSC82 vs HSP82. |
| GO:0050821 protein stabilization | IBA GO_REF:0000033 | ACCEPT | Summary: HSC82 stabilizes client proteins as part of its chaperone function. IBA annotation is appropriate. Reason: Protein stabilization is a core function of Hsp90. UniProt describes the role of HSC82 in stabilizing calcineurin (CNA2) under salt stress (PMID:11094077). Supporting Evidence: file:yeast/HSC82/HSC82-deep-research-falcon.md Supports stability and activation of diverse clients; proteome analyses and mutant studies show client-specific maturation defects and reduced abundance of client subsets when cycle steps are disrupted file:yeast/HSC82/HSC82-deep-research-falcon.md Direct Hsc82 binding to CNB1 and effects on CNA2/CNB1 complex state/activity support calcineurin as an Hsp90 client/regulatory target |
| GO:0034605 cellular response to heat | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: The phylogenetic annotation is biologically sound: HSC82 abundance contributes to growth at elevated temperature, although heat response is a conditional consequence of its chaperone capacity rather than the constitutive isoform's defining activity. Reason: The target itself is among the experimentally grounded descendants used for this IBA, and PMID:2674684 directly links HSC82/HSP82 gene dosage to high-temperature growth. Retain the conserved process annotation, but classify it as non-core because HSC82's core role is ATP-dependent client-protein chaperoning. Supporting Evidence: PMID:2674684 Cells carrying other combinations of the HSP82 and HSC82 mutations grew well at 25 degrees C, but their ability to grow at higher temperatures varied with gene copy number. |
| GO:0051082 unfolded protein binding | IBA GO_REF:0000033 | MODIFY | Summary: GO:0051082 is obsolete. HSC82 binds partially folded clients, but its molecular function is better represented by GO:0140662 (ATP-dependent protein folding chaperone). Reason: GO:0051082 is obsolete. HSC82 is an ATP-dependent foldase; while it does bind unfolded/non-native proteins as part of its chaperone cycle, the binding is coupled to ATP-driven conformational changes. The more appropriate term is GO:0140662 "ATP-dependent protein folding chaperone" which captures both the binding and the active folding mechanism. IDA evidence from PMID:9465043 demonstrated binding to denatured substrates, but this is part of the broader chaperone activity. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: GRANULARITY MISMATCH Sources checked: PANTHER:PTN000163527 Β· PAINT Hsp90 family node SUPPORTS TRANSFER The ancestral assertion captures genuine non-native-client binding, but the obsolete binding term should be replaced by the ATP-dependent chaperone activity term. Proposed replacements: ATP-dependent protein folding chaperone Supporting Evidence: file:yeast/HSC82/HSC82-deep-research-falcon.md Hsp90/Hsc82 is better captured by ATP-dependent chaperone cycle terms; mechanistic descriptions emphasize action on partially folded/late intermediates and cochaperone-regulated cycle steps rather than generic unfolded-substrate binding. |
| GO:0048471 perinuclear region of cytoplasm | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: The IBA places conserved Hsp90 activity in the perinuclear cytoplasm. HSC82 is principally cytosolic, so any perinuclear enrichment is a secondary spatial context rather than its defining localization. Reason: The PAINT assertion reflects a curated ancestral-node placement supported by several descendants, and there is no HSC82-specific evidence of localization loss or divergence. Retain it as non-core while noting that the retrieved HSC82 literature does not establish a stable perinuclear pool independently of the IBA. Propagation Review Root cause: NO FAILURE NON CORE Sources checked: PANTHER:PTN000163629 Β· PAINT Hsp90 family node SUPPORTS TRANSFER The ancestral localization is defensible for a mobile cytosolic Hsp90, and there is no evidence of target-specific loss; direct HSC82 imaging would still be needed to establish enrichment. |
| GO:0000166 nucleotide binding | IEA GO_REF:0000043 | MODIFY | Summary: IEA annotation from UniProt keyword mapping. True but too broad relative to ATP binding and ATPase-cycle annotations. Reason: HSC82 binds ATP through the conserved Hsp90 nucleotide-binding domain; generic nucleotide binding is accurate but less informative than ATP binding for this gene product. Replace the broad parent with ATP binding, while keeping ATP hydrolysis activity as the catalytic cycle term. Proposed replacements: ATP binding Supporting Evidence: file:yeast/HSC82/HSC82-deep-research-falcon.md True but much less informative than ATP binding/ATPase activity; GO should prefer the specific ATP-related terms |
| GO:0000492 box C/D snoRNP assembly | IEA GO_REF:0000117 | KEEP AS NON CORE | Summary: ARBA predicts box C/D snoRNP assembly, and the matching experimental annotation is supported by the Hsp90βTah1βPih1/R2TP study. Reason: PMID:18268103 showed that Hsp90, with Tah1, stabilizes Pih1 and thereby supports box C/D snoRNP accumulation. This is a legitimate downstream client-pathway role, but not the core biochemical function of HSC82. Supporting Evidence: PMID:18268103 Together with the Tah1 cofactor, Hsp90 functions to stabilize Pih1. As a consequence, the chaperone is shown to affect box C/D accumulation and maintenance, especially under stress conditions. |
| GO:0005524 ATP binding | IEA GO_REF:0000120 | ACCEPT | Summary: IEA annotation for ATP binding. Consistent with IBA and experimental evidence. Reason: Redundant with IBA annotation but correct. ATP binding is a core molecular function of HSC82. Supporting Evidence: file:yeast/HSC82/HSC82-deep-research-falcon.md N-terminal ATP-binding domain; ATP binding drives lid closure and N-terminal association; Hsc82 shows higher ATPase activity than Hsp82 at 30β37Β°C |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: IEA annotation for cytoplasm from UniProt subcellular location mapping. Correct. Reason: Consistent with HDA evidence for cytoplasmic localization (PMID:14562095). Supporting Evidence: file:yeast/HSC82/HSC82-deep-research-falcon.md Hsc82 is described as the constitutive cytosolic Hsp90 isoform; many experimental Hsc82 interactome/purification studies use cytosolic lysates, consistent with CC:cytosol annotations for both isoforms, with expression-level differences for HSC82 vs HSP82. |
| GO:0005739 mitochondrion | IEA GO_REF:0000044 | MARK AS OVER ANNOTATED | Summary: IEA annotation for mitochondrial localization from UniProt. Supported by HDA evidence. Reason: HSC82 has been detected in mitochondrial proteome studies (PMID:14576278, PMID:16823961), but organelle proteomics does not distinguish stable mitochondrial residence from co-purification of this abundant cytosolic chaperone. Targeted localization evidence is absent. Supporting Evidence: file:yeast/HSC82/HSC82-deep-research-falcon.md Some literature discusses cytosolic Hsp90/co-chaperones affecting mitochondrial biogenesis or preprotein handling, but that does not establish stable mitochondrial localization of Hsc82 |
| GO:0006457 protein folding | IEA GO_REF:0000120 | ACCEPT | Summary: IEA annotation for protein folding. Redundant with IBA but correct. Reason: Consistent with IBA and experimental annotations for protein folding involvement. Supporting Evidence: file:yeast/HSC82/HSC82-deep-research-falcon.md Hsp90/Hsc82 functions as an ATP-dependent folding chaperone for late intermediates/clients, and specific Hsp90 mutants that disrupt client loading/closing/reopening cause client-specific maturation defects and temperature-sensitive growth. |
| GO:0016887 ATP hydrolysis activity | IEA GO_REF:0000120 | ACCEPT | Summary: IEA annotation for ATP hydrolysis activity. Redundant with IBA and IDA but correct. Reason: Consistent with IBA and IDA (PMID:18492664) annotations for ATPase activity. Supporting Evidence: file:yeast/HSC82/HSC82-deep-research-falcon.md N-terminal ATP-binding domain; ATP binding drives lid closure and N-terminal association; Hsc82 shows higher ATPase activity than Hsp82 at 30β37Β°C file:yeast/HSC82/HSC82-deep-research-falcon.md Aha1 and Cpr6 stimulate ATPase activity of both isoforms, while Cdc37, Sba1/p23, and Sti1 inhibit with only minor isoform-specific differences. |
| GO:0043248 proteasome assembly | IEA GO_REF:0000117 | KEEP AS NON CORE | Summary: ARBA prediction for proteasome assembly involvement. Supported by IMP evidence. Reason: Supported by IMP evidence (PMID:12853471). Hsp90 assists in proteasome assembly as one of its client-dependent functions. Not a core function of HSC82 per se. |
| GO:0051082 unfolded protein binding | IEA GO_REF:0000120 | MODIFY | Summary: IEA annotation to an obsolete term; the underlying chaperone biology is valid but GO:0140662 is the current informative molecular-function term. Reason: GO:0051082 is obsolete. It should be replaced with GO:0140662 "ATP-dependent protein folding chaperone" which better captures the active chaperone mechanism. Proposed replacements: ATP-dependent protein folding chaperone Supporting Evidence: file:yeast/HSC82/HSC82-deep-research-falcon.md Hsp90/Hsc82 is better captured by ATP-dependent chaperone cycle terms; mechanistic descriptions emphasize action on partially folded/late intermediates and cochaperone-regulated cycle steps rather than generic unfolded-substrate binding. |
| GO:0140662 ATP-dependent protein folding chaperone | IEA GO_REF:0000002 | ACCEPT | Summary: IEA annotation from InterPro for ATP-dependent protein folding chaperone. This is the correct and most informative molecular function term for HSC82. Reason: GO:0140662 is the ideal molecular function term for HSC82/Hsp90. It captures both the ATP dependence and the protein folding chaperone activity. This should be considered the primary MF annotation for HSC82. Supporting Evidence: file:yeast/HSC82/HSC82-deep-research-falcon.md Hsp90/Hsc82 functions as an ATP-dependent folding chaperone for late intermediates/clients, and specific Hsp90 mutants that disrupt client loading/closing/reopening cause client-specific maturation defects and temperature-sensitive growth. |
| GO:0005515 protein binding | IPI PMID:11805826 Functional organization of the yeast proteome by systematic ... | MARK AS OVER ANNOTATED | Summary: IPI from large-scale protein complex study. Uninformative "protein binding" annotation. Reason: "Protein binding" is uninformative for a molecular chaperone that by definition binds many proteins. The more informative annotation is GO:0140662 (ATP-dependent protein folding chaperone). |
| GO:0005515 protein binding | IPI PMID:11805837 Systematic identification of protein complexes in Saccharomy... | MARK AS OVER ANNOTATED | Summary: IPI from mass spectrometry study. Uninformative "protein binding" annotation. Reason: Uninformative "protein binding" for a chaperone. |
| GO:0005515 protein binding | IPI PMID:15699485 Analysis of polyubiquitin conjugates reveals that the Rpn10 ... | MARK AS OVER ANNOTATED | Summary: IPI from polyubiquitin conjugate study. Reason: Uninformative "protein binding" for a chaperone. |
| GO:0005515 protein binding | IPI PMID:15766533 Navigating the chaperone network: an integrative map of phys... | MARK AS OVER ANNOTATED | Summary: IPI from large-scale chaperone network study (Zhao et al 2005). Reason: Uninformative "protein binding" for a chaperone. |
| GO:0005515 protein binding | IPI PMID:16429126 Proteome survey reveals modularity of the yeast cell machine... | MARK AS OVER ANNOTATED | Summary: IPI from proteome survey. Reason: Uninformative "protein binding" for a chaperone. |
| GO:0005515 protein binding | IPI PMID:16554755 Global landscape of protein complexes in the yeast Saccharom... | MARK AS OVER ANNOTATED | Summary: IPI from large-scale protein complex study (Krogan et al 2006). Reason: Uninformative "protein binding" for a chaperone. |
| GO:0005515 protein binding | IPI PMID:18719252 High-quality binary protein interaction map of the yeast int... | MARK AS OVER ANNOTATED | Summary: IPI from high-quality binary interaction map. Reason: Uninformative "protein binding" for a chaperone. |
| GO:0005515 protein binding | IPI PMID:19536198 An atlas of chaperone-protein interactions in Saccharomyces ... | MARK AS OVER ANNOTATED | Summary: IPI from atlas of chaperone-protein interactions. Reason: Uninformative "protein binding" for a chaperone. |
| GO:0005515 protein binding | IPI PMID:21734642 Combinatorial depletion analysis to assemble the network arc... | MARK AS OVER ANNOTATED | Summary: IPI from SAGA/ADA complex study. Reason: Uninformative "protein binding" for a chaperone. |
| GO:0005515 protein binding | IPI PMID:23217712 CDK-dependent Hsp70 Phosphorylation controls G1 cyclin abund... | MARK AS OVER ANNOTATED | Summary: IPI from CDK-dependent Hsp70 phosphorylation study. Reason: Uninformative "protein binding" for a chaperone. |
| GO:0005515 protein binding | IPI PMID:25073740 Molecular architecture and function of the SEA complex, a mo... | MARK AS OVER ANNOTATED | Summary: IPI from protein interaction study. Reason: Uninformative "protein binding" for a chaperone. |
| GO:0005515 protein binding | IPI PMID:31454312 The role of structural pleiotropy and regulatory evolution i... | MARK AS OVER ANNOTATED | Summary: IPI from structural pleiotropy study of Hsp90 paralogs. Documents HSP82-HSC82 heterodimerization. Reason: While the HSP82-HSC82 heterodimerization is biologically interesting, "protein binding" is uninformative. The heterodimerization could be captured by GO:0042802 (identical protein binding) or a more specific term. |
| GO:0005515 protein binding | IPI PMID:37070168 RNA-dependent interactome allows network-based assignment of... | MARK AS OVER ANNOTATED | Summary: IPI from RNA-dependent interactome study. Reason: Uninformative "protein binding" for a chaperone. |
| GO:0005515 protein binding | IPI PMID:37968396 The social and structural architecture of the yeast protein ... | MARK AS OVER ANNOTATED | Summary: IPI from yeast protein interactome architecture study. Reason: Uninformative "protein binding" for a chaperone. |
| GO:0005515 protein binding | IPI PMID:9819421 CNS1 encodes an essential p60/Sti1 homolog in Saccharomyces ... | MARK AS OVER ANNOTATED | Summary: IPI from Cns1/Hsp90 interaction study. Reason: Uninformative "protein binding" for a chaperone. |
| GO:0070482 response to oxygen levels | NAS PMID:9632766 Molecular mechanism governing heme signaling in yeast: a hig... | KEEP AS NON CORE | Summary: The NAS annotation extrapolates HAP1/heme-signaling evidence to HSC82, but the accessible abstract explicitly identifies the inducible paralog Hsp82 rather than Hsc82. Reason: The cached abstract identifies Hsp82, not Hsc82, in the HAP1 complex. Because this NAS annotation comes from the curator and the two cytosolic Hsp90 paralogs have substantially shared client repertoires, retain the family-level client-pathway inference as non-core while treating the HSC82 attribution as unverified paralog extrapolation. Supporting Evidence: PMID:9632766 Our data suggest that this complex contains HAP1 and four other cellular proteins including Hsp82 and Ydj1. |
| GO:0005737 cytoplasm | HDA PMID:14562095 Global analysis of protein localization in budding yeast. | ACCEPT | Summary: High-throughput GFP localization data confirming cytoplasm. Reason: Global protein localization study. Core localization of HSC82. Supporting Evidence: file:yeast/HSC82/HSC82-deep-research-falcon.md Hsc82 is described as the constitutive cytosolic Hsp90 isoform; many experimental Hsc82 interactome/purification studies use cytosolic lysates, consistent with CC:cytosol annotations for both isoforms, with expression-level differences for HSC82 vs HSP82. |
| GO:0005739 mitochondrion | HDA PMID:14576278 The proteome of Saccharomyces cerevisiae mitochondria. | MARK AS OVER ANNOTATED | Summary: HDA for mitochondrial localization from mitochondrial proteome study. Reason: Detection in a mitochondrial proteome does not establish stable organelle residence for this abundant cytosolic chaperone; targeted localization evidence is absent. Supporting Evidence: file:yeast/HSC82/HSC82-deep-research-falcon.md Some literature discusses cytosolic Hsp90/co-chaperones affecting mitochondrial biogenesis or preprotein handling, but that does not establish stable mitochondrial localization of Hsc82 |
| GO:0005739 mitochondrion | HDA PMID:16823961 Toward the complete yeast mitochondrial proteome: multidimen... | MARK AS OVER ANNOTATED | Summary: Additional HDA for mitochondrial localization from mitochondrial proteomics. Reason: A second mitochondrial proteomics detection remains vulnerable to co-purification and does not establish a functional mitochondrial pool without targeted localization evidence. Supporting Evidence: file:yeast/HSC82/HSC82-deep-research-falcon.md Some literature discusses cytosolic Hsp90/co-chaperones affecting mitochondrial biogenesis or preprotein handling, but that does not establish stable mitochondrial localization of Hsc82 |
| GO:0005886 plasma membrane | HDA PMID:16622836 The plasma membrane proteome of Saccharomyces cerevisiae and... | MARK AS OVER ANNOTATED | Summary: HDA for plasma membrane localization from plasma membrane proteomics study. Reason: Detection in a plasma-membrane proteome does not establish stable membrane residence for this abundant soluble cytosolic chaperone; targeted localization evidence is absent. |
| GO:0034605 cellular response to heat | IMP PMID:2674684 hsp82 is an essential protein that is required in higher con... | KEEP AS NON CORE | Summary: Mutant and dosage evidence shows that HSC82 contributes to elevated-temperature growth, a valid conditional phenotype downstream of its constitutive chaperone activity. Reason: PMID:2674684 directly tested both yeast cytosolic Hsp90 genes and found that higher-temperature growth depends on their combined dosage. Retain the experimental process annotation, but classify it as non-core because it describes a stress phenotype rather than HSC82's primary molecular role. Supporting Evidence: PMID:2674684 Cells carrying other combinations of the HSP82 and HSC82 mutations grew well at 25 degrees C, but their ability to grow at higher temperatures varied with gene copy number. |
| GO:0000492 box C/D snoRNP assembly | IMP PMID:18268103 Molecular chaperone Hsp90 stabilizes Pih1/Nop17 to maintain ... | KEEP AS NON CORE | Summary: IMP evidence connects the Hsp90βTah1βPih1/R2TP pathway to box C/D snoRNP accumulation and maintenance. Reason: Full text is cached. The authors distinguish Hsp82 from Hsc82 when necessary and otherwise use "Hsp90" for the two nearly identical cytosolic isoforms; their experiments show Hsp90-dependent Pih1 stabilization and snoRNP maintenance. This supports a real but downstream, non-core role. Supporting Evidence: PMID:18268103 In this paper, the term Hsp90 is used when we do not explicitly distinguish between Hsp82 and Hsc82. PMID:18268103 Together with the Tah1 cofactor, Hsp90 functions to stabilize Pih1. As a consequence, the chaperone is shown to affect box C/D accumulation and maintenance, especially under stress conditions. |
| GO:0000723 telomere maintenance | IMP PMID:17954556 The hsp90 molecular chaperone modulates multiple telomerase ... | KEEP AS NON CORE | Summary: The paper supports an Hsp90 requirement for telomerase activity, but the accessible abstract reports experiments with Hsp82 alleles and does not establish the contribution of HSC82 specifically. Reason: The cached abstract reports that telomere length and telomerase occupancy are yeast-Hsp90 dependent but names Hsp82p in the mechanistic assays. Defer to the experimental curator and retain the family-level pathway annotation as non-core without claiming HSC82-specific evidence that is absent from the cache. Supporting Evidence: PMID:17954556 Importantly, telomere length and telomerase telomere occupancy was yeast Hsp90 dependent. |
| GO:0006457 protein folding | IMP PMID:7791797 Mutational analysis of Hsp90 function: interactions with a s... | ACCEPT | Summary: IMP evidence for protein folding from early characterization study. Reason: Core biological process for HSC82/Hsp90. Directly demonstrates the role in protein folding. Supporting Evidence: file:yeast/HSC82/HSC82-deep-research-falcon.md Hsp90/Hsc82 functions as an ATP-dependent folding chaperone for late intermediates/clients, and specific Hsp90 mutants that disrupt client loading/closing/reopening cause client-specific maturation defects and temperature-sensitive growth. |
| GO:0016887 ATP hydrolysis activity | IDA PMID:18492664 Intra- and intermonomer interactions are required to synergi... | ACCEPT | Summary: Direct biochemical assays of purified yeast Hsc82 establish ATP hydrolysis and show how cis- and trans-monomer contacts stabilize the hydrolysis-competent conformation. Reason: Core molecular function. Direct biochemical measurement of ATPase activity showing that both intra- and intermonomer interactions synergistically facilitate ATP hydrolysis. Supporting Evidence: PMID:18492664 Together, these data indicate that both the cis monomer and the trans monomer and the intradomain and interdomain interactions cooperatively stabilize the active conformation of each active site and help explain the importance of dimer formation. |
| GO:0043248 proteasome assembly | IMP PMID:12853471 The molecular chaperone Hsp90 plays a role in the assembly a... | KEEP AS NON CORE | Summary: Yeast loss-of-function and reassembly experiments support Hsp90 involvement in ATP-dependent 26S proteasome assembly and maintenance. Reason: PMID:12853471 provides direct yeast Hsp90 evidence, although the cache is abstract-only and does not resolve which cytosolic isoform supplied the assayed activity. Defer to the experimental curator and retain this as a secondary pathway role. Supporting Evidence: PMID:12853471 Functional loss of Hsp90 using a temperature-sensitive mutant in yeast caused dissociation of the 26S proteasome. |
| GO:0051082 unfolded protein binding | IDA PMID:9465043 Two chaperone sites in Hsp90 differing in substrate specific... | MODIFY | Summary: The biochemical study supports binding to partially folded proteins and peptides, but the imported GO term is obsolete. Reason: While the experimental evidence is solid (Hsp90 binds non-native substrates), GO:0051082 is obsolete. The binding of unfolded proteins is part of the ATP-dependent chaperone mechanism, better captured by GO:0140662 "ATP-dependent protein folding chaperone." Proposed replacements: ATP-dependent protein folding chaperone Supporting Evidence: PMID:9465043 The C-terminal fragment binds to partially folded proteins in an ATP-independent way potentially regulated by cochaperones. file:yeast/HSC82/HSC82-deep-research-falcon.md Hsp90/Hsc82 is better captured by ATP-dependent chaperone cycle terms; mechanistic descriptions emphasize action on partially folded/late intermediates and cochaperone-regulated cycle steps rather than generic unfolded-substrate binding. |
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Download this section (compressed HTML)Q: Under non-stress conditions, which Hsp90 clients are predominantly chaperoned by the constitutive HSC82 isoform versus the inducible HSP82, and how does the relative paralog abundance shape clientele selection?
Q: What is the functional significance of HSP82-HSC82 heterodimer formation, and is heterodimerization required for engagement of specific clients or co-chaperones?
Q: Do mitochondrial and plasma-membrane-associated HSC82 pools have specialized functions (e.g., mitochondrial protein import support, membrane raft proteostasis), or do they reflect non-functional spillover?
Experiment: Quantitatively profile co-chaperone occupancy and client maturation efficiency in single (hsc82Ξ, hsp82Ξ) and double-paralog deletion/over-expression strains by AP-MS and Western to deconvolve constitutive vs inducible chaperone contributions.
Experiment: Reconstitute HSP82-HSC82 heterodimers in vitro with purified proteins and a panel of co-chaperones (Sti1, Aha1, Sba1, Cdc37) and measure ATPase rates plus client (e.g., glucocorticoid receptor) activation efficiency relative to the homodimers.
Experiment: Perform proximity-labeling proteomics (TurboID) of HSC82 in mitochondrial and plasma-membrane subfractions versus cytosol to test whether minor pools have distinctive interactomes.
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