CHS7 encodes an endoplasmic-reticulum membrane export chaperone for the chitin synthase Chs3, promoting Chs3 folding/proteostasis, ER-to-Golgi export, and normal chitin synthase III-dependent cell wall chitin deposition.
Definition: A protein folding chaperone activity that binds or escorts a chitin synthase client in the endoplasmic reticulum to promote its productive folding, ER quality-control evasion, and export toward the Golgi.
Justification: Chs7 is not a generic unfolded-protein binder; the yeast evidence supports a dedicated export-chaperone activity for Chs3/chitin synthase III that is more specific than existing chaperone terms. The 2023 Sanchez et al. MBoC study strengthens this by showing that Chs7 also functions as a degron shield, masking Chs3 cytosolic degrons to prevent ERAD-C targeting.
Parent term: protein folding chaperone
Supporting Evidence:
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0006031
chitin biosynthetic process
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: chitin biosynthetic process reviewed for CHS7: ACCEPT.
Reason: Retain as a core biological-process consequence of Chs7-dependent Chs3 maturation and export; loss of CHS7 strongly reduces chitin synthase III output and cell wall chitin deposition.
Supporting Evidence:
file:yeast/CHS7/CHS7-deep-research-falcon.md
Loss of CHS7 causes **ER retention of Chs3**, severe reduction of **cell wall chitin** and **CSIII activity**
|
|
GO:0005789
endoplasmic reticulum membrane
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: endoplasmic reticulum membrane reviewed for CHS7: ACCEPT.
Reason: Retain as the best-supported cellular location; Chs7 is a multipass ER membrane protein acting at the Chs3 ER export step.
Supporting Evidence:
file:yeast/CHS7/CHS7-deep-research-falcon.md
functional tagged Chs7 showed **perinuclear/ER localization** and co-localization with the ER marker Sec63p
|
|
GO:0006457
protein folding
|
IBA
GO_REF:0000033 |
ACCEPT |
Summary: protein folding reviewed for CHS7: ACCEPT.
Reason: Retain because Chs7 functions in client folding/proteostasis of the polytopic Chs3 cargo, even though the more specific role is a dedicated export chaperone.
Supporting Evidence:
file:yeast/CHS7/CHS7-deep-research-falcon.md
describe Chs7 as a **specific ER chaperone** that prevents Chs3 aggregation and promotes ER exit via **COPII loading**
|
|
GO:0051082
unfolded protein binding
|
IBA
GO_REF:0000033 |
MODIFY |
Summary: unfolded protein binding reviewed for CHS7: MODIFY.
Reason: The generic unfolded-protein binding term is less informative than the supported Chs3-specific chaperone/escort role; replace with protein folding chaperone.
Proposed replacements:
protein folding chaperone
Supporting Evidence:
file:yeast/CHS7/CHS7-deep-research-falcon.md
Chs7 is an export chaperone in the sense that **Chs3 ER exit depends on Chs7**
|
|
GO:0005789
endoplasmic reticulum membrane
|
IEA
GO_REF:0000044 |
ACCEPT |
Summary: endoplasmic reticulum membrane reviewed for CHS7: ACCEPT.
Reason: Retain as the best-supported cellular location; Chs7 is a multipass ER membrane protein acting at the Chs3 ER export step.
Supporting Evidence:
file:yeast/CHS7/CHS7-deep-research-falcon.md
functional tagged Chs7 showed **perinuclear/ER localization** and co-localization with the ER marker Sec63p
|
|
GO:0015031
protein transport
|
IEA
GO_REF:0000043 |
MODIFY |
Summary: protein transport reviewed for CHS7: MODIFY.
Reason: General protein transport is too broad for the curated evidence; Chs7 specifically promotes Chs3 exit from the ER toward the Golgi.
Proposed replacements:
endoplasmic reticulum to Golgi vesicle-mediated transport
Supporting Evidence:
file:yeast/CHS7/CHS7-deep-research-falcon.md
Chs7 is required for exit of Chs3 from the ER
|
|
GO:0071555
cell wall organization
|
IEA
GO_REF:0000043 |
KEEP AS NON CORE |
Summary: cell wall organization reviewed for CHS7: KEEP_AS_NON_CORE.
Reason: Keep as a valid downstream phenotype of impaired Chs3-dependent chitin deposition, but not the direct molecular role of Chs7.
Supporting Evidence:
file:yeast/CHS7/CHS7-deep-research-falcon.md
These quantitative data support the central functional claim that CHS7 is required for normal Chs3/CSIII-dependent chitin deposition
|
|
GO:0005515
protein binding
|
IPI
PMID:18467557 An in vivo map of the yeast protein interactome. |
MARK AS OVER ANNOTATED |
Summary: protein binding reviewed for CHS7: MARK_AS_OVER_ANNOTATED.
Reason: Protein binding is too generic; the Chs3 interaction is better captured by a specific chaperone/export role.
Supporting Evidence:
file:yeast/CHS7/CHS7-deep-research-falcon.md
Chs7 **physically interacts** with full-length Chs3 and certain truncated Chs3 forms
|
|
GO:0005515
protein binding
|
IPI
PMID:37968396 The social and structural architecture of the yeast protein ... |
MARK AS OVER ANNOTATED |
Summary: protein binding reviewed for CHS7: MARK_AS_OVER_ANNOTATED.
Reason: Protein binding is too generic; the Chs3 interaction is better captured by a specific chaperone/export role.
Supporting Evidence:
file:yeast/CHS7/CHS7-deep-research-falcon.md
Chs7 **physically interacts** with full-length Chs3 and certain truncated Chs3 forms
|
|
GO:0005783
endoplasmic reticulum
|
HDA
PMID:22842922 Dissecting DNA damage response pathways by analysing protein... |
ACCEPT |
Summary: endoplasmic reticulum reviewed for CHS7: ACCEPT.
Reason: Retain as a supported broader ER localization, consistent with the more precise ER membrane annotation.
Supporting Evidence:
file:yeast/CHS7/CHS7-deep-research-falcon.md
functional tagged Chs7 showed **perinuclear/ER localization** and co-localization with the ER marker Sec63p
|
|
GO:0005783
endoplasmic reticulum
|
HDA
PMID:26928762 One library to make them all: streamlining the creation of y... |
ACCEPT |
Summary: endoplasmic reticulum reviewed for CHS7: ACCEPT.
Reason: Retain as a supported broader ER localization, consistent with the more precise ER membrane annotation.
Supporting Evidence:
file:yeast/CHS7/CHS7-deep-research-falcon.md
functional tagged Chs7 showed **perinuclear/ER localization** and co-localization with the ER marker Sec63p
|
|
GO:0005934
cellular bud tip
|
HDA
PMID:22842922 Dissecting DNA damage response pathways by analysing protein... |
KEEP AS NON CORE |
Summary: cellular bud tip reviewed for CHS7: KEEP_AS_NON_CORE.
Reason: Keep as context-dependent localization associated with Chs3/chitin deposition biology, not as the primary site of Chs7 action.
Supporting Evidence:
file:yeast/CHS7/CHS7-deep-research-falcon.md
Chs7 can also **exit the ER with Chs3** and co-localize with Chs3 at the bud neck and intracellular puncta
|
|
GO:0005935
cellular bud neck
|
HDA
PMID:22842922 Dissecting DNA damage response pathways by analysing protein... |
KEEP AS NON CORE |
Summary: cellular bud neck reviewed for CHS7: KEEP_AS_NON_CORE.
Reason: Keep as context-dependent bud-neck localization associated with chitin deposition, not as the core ER export role.
Supporting Evidence:
file:yeast/CHS7/CHS7-deep-research-falcon.md
Chs7 can also **exit the ER with Chs3** and co-localize with Chs3 at the bud neck and intracellular puncta
|
|
GO:0005628
prospore membrane
|
HDA
PMID:24390141 A visual screen of protein localization during sporulation i... |
KEEP AS NON CORE |
Summary: prospore membrane reviewed for CHS7: KEEP_AS_NON_CORE.
Reason: Keep as a sporulation-context localization observation, peripheral to the core ER chaperone/export function.
Supporting Evidence:
file:yeast/CHS7/CHS7-deep-research-falcon.md
Reported induction includes **~24-fold during sporulation**
|
|
GO:0005935
cellular bud neck
|
IDA
PMID:29405545 The chaperone Chs7 forms a stable complex with Chs3 and prom... |
KEEP AS NON CORE |
Summary: cellular bud neck reviewed for CHS7: KEEP_AS_NON_CORE.
Reason: Keep as context-dependent bud-neck localization associated with chitin deposition, not as the core ER export role.
Supporting Evidence:
file:yeast/CHS7/CHS7-deep-research-falcon.md
Chs7 can also **exit the ER with Chs3** and co-localize with Chs3 at the bud neck and intracellular puncta
|
|
GO:0005789
endoplasmic reticulum membrane
|
IDA
PMID:10366589 Chs7p, a new protein involved in the control of protein expo... |
ACCEPT |
Summary: endoplasmic reticulum membrane reviewed for CHS7: ACCEPT.
Reason: Retain as the best-supported cellular location; Chs7 is a multipass ER membrane protein acting at the Chs3 ER export step.
Supporting Evidence:
file:yeast/CHS7/CHS7-deep-research-falcon.md
functional tagged Chs7 showed **perinuclear/ER localization** and co-localization with the ER marker Sec63p
|
|
GO:0006031
chitin biosynthetic process
|
IMP
PMID:10366589 Chs7p, a new protein involved in the control of protein expo... |
ACCEPT |
Summary: chitin biosynthetic process reviewed for CHS7: ACCEPT.
Reason: Retain as a core biological-process consequence of Chs7-dependent Chs3 maturation and export; loss of CHS7 strongly reduces chitin synthase III output and cell wall chitin deposition.
Supporting Evidence:
file:yeast/CHS7/CHS7-deep-research-falcon.md
Loss of CHS7 causes **ER retention of Chs3**, severe reduction of **cell wall chitin** and **CSIII activity**
|
|
GO:0006457
protein folding
|
IMP
PMID:15623581 Specialized membrane-localized chaperones prevent aggregatio... |
ACCEPT |
Summary: protein folding reviewed for CHS7: ACCEPT.
Reason: Retain because Chs7 functions in client folding/proteostasis of the polytopic Chs3 cargo, even though the more specific role is a dedicated export chaperone.
Supporting Evidence:
file:yeast/CHS7/CHS7-deep-research-falcon.md
describe Chs7 as a **specific ER chaperone** that prevents Chs3 aggregation and promotes ER exit via **COPII loading**
|
|
GO:0006888
endoplasmic reticulum to Golgi vesicle-mediated transport
|
IDA
PMID:10366589 Chs7p, a new protein involved in the control of protein expo... |
ACCEPT |
Summary: endoplasmic reticulum to Golgi vesicle-mediated transport reviewed for CHS7: ACCEPT.
Reason: Retain as a core process: the strongest mechanistic evidence places Chs7 at Chs3 ER exit and ER-to-Golgi trafficking.
Supporting Evidence:
file:yeast/CHS7/CHS7-deep-research-falcon.md
Chs7 is an export chaperone in the sense that **Chs3 ER exit depends on Chs7**
|
|
GO:0051082
unfolded protein binding
|
IMP
PMID:15623581 Specialized membrane-localized chaperones prevent aggregatio... |
MODIFY |
Summary: unfolded protein binding reviewed for CHS7: MODIFY.
Reason: The generic unfolded-protein binding term is less informative than the supported Chs3-specific chaperone/escort role; replace with protein folding chaperone.
Proposed replacements:
protein folding chaperone
Supporting Evidence:
file:yeast/CHS7/CHS7-deep-research-falcon.md
describe Chs7 as a **specific ER chaperone** that prevents Chs3 aggregation and promotes ER exit via **COPII loading**
|
Q: Does Chs7 have physiologically important clients other than Chs3, or is its conserved role essentially dedicated to chitin synthase export?
Q: Which Chs3 surfaces are shielded by Chs7 during ER quality control and ERAD avoidance?
Experiment: Map Chs3 regions that require Chs7 using endogenous tagged Chs3 truncation or degron mutants, ER export assays, co-immunoprecipitation, and ERAD/INMAD pathway perturbations.
Hypothesis: Chs7 promotes Chs3 ER export by masking Chs3 degrons while maintaining an export-competent conformation.
Type: client-mapping and trafficking assay
provider: falcon
model: Edison Scientific Literature
cached: false
start_time: '2026-05-04T10:54:41.387282'
end_time: '2026-05-04T11:06:55.529111'
duration_seconds: 734.14
template_file: templates/gene_research_go_focused.md
template_variables:
organism: yeast
gene_id: CHS7
gene_symbol: CHS7
uniprot_accession: P38843
protein_description: 'RecName: Full=Chitin synthase export chaperone;'
gene_info: Name=CHS7; OrderedLocusNames=YHR142W;
organism_full: Saccharomyces cerevisiae (strain ATCC 204508 / S288c) (Baker's yeast).
protein_family: Belongs to the CHS7 family. .
protein_domains: Chs7. (IPR022057); Chs7 (PF12271)
provider_config:
timeout: 600
max_retries: 3
parameters:
allowed_domains: []
temperature: 0.1
citation_count: 28
BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.
DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'CHS7' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information
Please provide a comprehensive research report on the gene CHS7 (gene ID: CHS7, UniProt: P38843) in yeast.
The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
Question: You are an expert researcher providing comprehensive, well-cited information.
Provide detailed information focusing on:
1. Key concepts and definitions with current understanding
2. Recent developments and latest research (prioritize 2023-2024 sources)
3. Current applications and real-world implementations
4. Expert opinions and analysis from authoritative sources
5. Relevant statistics and data from recent studies
Format as a comprehensive research report with proper citations. Include URLs and publication dates where available.
Always prioritize recent, authoritative sources and provide specific citations for all major claims.
BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.
DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'CHS7' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information
Please provide a comprehensive research report on the gene CHS7 (gene ID: CHS7, UniProt: P38843) in yeast.
The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
CHS7 (YHR142W; UniProt P38843) encodes Chs7, a small multipass membrane protein that functions primarily as a client-specific export chaperone/escort required for endoplasmic reticulum (ER) exit and productive biogenesis of the major chitin synthase Chs3 (chitin synthase III; CSIII). Loss of CHS7 causes ER retention of Chs3, severe reduction of cell wall chitin and CSIII activity, and associated cell-wall and developmental phenotypes. More recent work (2022–2023) reframes Chs7 as part of a multi-layered proteostasis/quality-control network that prevents Chs3 aggregation and masks cytosolic degrons to avoid ER-associated degradation (ERAD). (trilla1999chs7panew pages 4-5, sanchez2022chitinsynthesisin pages 4-6, sanchez2023multiplequalitycontrol pages 4-6)
Trilla et al. experimentally defined CHS7 as YHR142W and described its product (Chs7p) as a ~316-aa, 6–7 transmembrane protein involved in ER export control specifically tied to chitin synthesis regulation (publication: June 1999, Journal of Cell Biology, https://doi.org/10.1083/jcb.145.6.1153). (trilla1999chs7panew pages 4-5, trilla1999chs7panew pages 5-6)
In budding yeast, most chitin in the wall is produced by Chs3/CSIII, a multipass membrane enzyme whose trafficking is highly regulated. Chs7 is “export chaperone” in the sense that Chs3 ER exit depends on Chs7, and without Chs7 Chs3 remains ER-localized despite being synthesized and core-glycosylated. (trilla1999chs7panew pages 5-6, sanchez2022chitinsynthesisin pages 3-4)
A key conceptual update from recent synthesis is that the Chs3/Chs7 system is treated as a paradigm for intracellular trafficking of integral membrane proteins—Chs3 recapitulates many canonical trafficking steps (ER folding, COPII export, Golgi/TGN sorting, endocytosis, recycling, degradation), with Chs7 acting at the earliest “licensing” step. (sanchez2022chitinsynthesisin pages 3-4)
A central experimental result is that chs7Δ mutants retain Chs3 in the ER (“all the Chs3p-3XHA remained in the ER”), demonstrating Chs7 is required for Chs3 export from the ER. (trilla1999chs7panew pages 6-7, trilla1999chs7panew media afaeb15d)
Chs7 is also a limiting factor for functional CSIII: co-overexpression of CHS3 and CHS7 increased total CSIII almost fourfold, whereas basal activity increased only ~1.3-fold, consistent with increased export/availability of an otherwise ER-limited pool of Chs3. (trilla1999chs7panew pages 7-8)
In the original primary study, functional tagged Chs7 showed perinuclear/ER localization and co-localization with the ER marker Sec63p (ER fractionation and imaging). (trilla1999chs7panew pages 5-6, trilla1999chs7panew media 93a4edff)
Later work (thesis-level evidence in the retrieved corpus) argues Chs7 is not exclusively ER-resident: it can exit the ER with Chs3 and co-localize with Chs3 at the bud neck and intracellular puncta, remaining associated and contributing to activity at the surface. While not a 2023–2024 peer-reviewed source in the retrieved set, it provides a mechanistic model consistent with complex persistence noted in the 2022 review. (dharwada2016intracellulartraffickingof pages 40-45, dharwada2016intracellulartraffickingof pages 50-54)
A genetic-interaction synthesis explicitly positions CHS7 at the ER step: Chs7 is required for exit of Chs3 from the ER, whereas Chs5/Chs6 are involved in transport of Chs3 from “chitosomes” (TGN pool) to the plasma membrane. (publication: Feb 2005, BMC Genetics, https://doi.org/10.1186/1471-2156-6-8). (lesage2005aninteractionalnetwork pages 1-2)
Sánchez & Roncero (publication: Oct 2022, Int. J. Mol. Sci., https://doi.org/10.3390/ijms232012251) integrate decades of trafficking work and describe Chs7 as a specific ER chaperone that prevents Chs3 aggregation and promotes ER exit via COPII loading, with Erv14 acting as a cargo receptor; they also note that the Chs3–Chs7 complex can persist along the secretory route, potentially affecting later steps and/or activity. (sanchez2022chitinsynthesisin pages 4-6)
This review further emphasizes that Chs3 folding/assembly is monitored by multiple checkpoints and that trafficking regulation is central to controlling chitin deposition (i.e., chitin output is a trafficking problem as much as an enzymology problem). (sanchez2022chitinsynthesisin pages 3-4)
Sanchez et al. (publication: Dec 2023, Molecular Biology of the Cell, https://doi.org/10.1091/mbc.e23-05-0186) provide direct evidence that Chs7 is not merely a passive escort: it masks cytosolic degrons in Chs3, preventing Doa10-mediated ERAD-C targeting when Chs3 is retained in the ER. (sanchez2023multiplequalitycontrol pages 11-13, sanchez2023multiplequalitycontrol pages 9-11)
Key mechanistic points supported in the retrieved excerpts include:
- Chs7 physically interacts with full-length Chs3 and certain truncated Chs3 forms (co-immunoprecipitation). (sanchez2023multiplequalitycontrol pages 11-13)
- In a chs7Δ background, Chs3 constructs can become more ERAD-sensitive; doa10Δ reverses instability for at least some constructs, consistent with Chs7-dependent shielding from ERAD-C. (sanchez2023multiplequalitycontrol pages 11-13, sanchez2023multiplequalitycontrol pages 9-11)
- Chs3 that evades canonical ERAD can redistribute to the inner nuclear membrane (INM) and be degraded by INMAD (Asi complex), framing INMAD as a downstream safeguard for polytopic membrane proteins. (sanchez2023multiplequalitycontrol pages 13-15, sanchez2023multiplequalitycontrol pages 1-2)
Overall, the 2023 study advances the field from “Chs7 is required for export” to “Chs7 is part of a layered ER proteostasis logic that determines whether Chs3 is exported, retained, or degraded.” (sanchez2023multiplequalitycontrol pages 4-6, sanchez2023multiplequalitycontrol pages 11-13)
Within the retrieved 2024 corpus for this run, CHS7 is primarily cited as a canonical example of an ER export chaperone for chitin synthases, rather than being the subject of new S. cerevisiae CHS7 experiments. Accordingly, the most direct “latest” primary evidence in the retrieved set is the 2023 MBoC work. (sanchez2023multiplequalitycontrol pages 4-6)
The Chs3/Chs7 module is widely used as a model polytopic membrane-protein cargo to interrogate principles of ER folding, COPII export, Golgi/TGN sorting, endocytic recycling, and degradation pathways. This is explicit in the 2022 review’s framing of Chs3 as a paradigm cargo whose lifecycle covers most canonical trafficking steps; Chs7 is the dedicated accessory/chaperone controlling the critical ER exit step. (sanchez2022chitinsynthesisin pages 3-4, sanchez2022chitinsynthesisin pages 4-6)
Chitin is absent from mammalian cells and is an established antifungal-relevant cell wall component. While CHS7 itself is not an enzyme (and thus not a direct catalytic target), it is essential for productive trafficking of the major chitin synthase and therefore links mechanistically to cell wall robustness. The review emphasizes sustained interest in chitin synthesis regulation as relevant to antifungal approaches. (sanchez2022chitinsynthesisin pages 4-6)
Sánchez & Roncero argue that regulation of chitin deposition (especially by Chs3) is fundamentally a trafficking and localization problem, because activity depends on correct compartmental progression and polarized delivery, not only on catalytic capability. In this framework, Chs7 is a decisive early determinant because it controls whether Chs3 is competent to leave the ER and enter the regulated trafficking itinerary. (sanchez2022chitinsynthesisin pages 3-4, sanchez2022chitinsynthesisin pages 4-6)
Sanchez et al. emphasize that several complementary QC mechanisms (N-glycosylation-dependent ERAD-L avoidance, Chs7-dependent ERAD-C degron masking, and INMAD as a late safeguard) together maintain homeostasis for a stable but failure-prone polytopic enzyme. This presents a broader expert-level conclusion: dedicated chaperones like Chs7 can simultaneously function as folding/escort factors and “degron shields” that determine whether a client is trafficked or degraded. (sanchez2023multiplequalitycontrol pages 1-2, sanchez2023multiplequalitycontrol pages 11-13, sanchez2023multiplequalitycontrol pages 13-15)
In Trilla et al. (1999), chs7Δ mutants exhibit a dramatic reduction in chitin synthesis outputs:
- Cell wall chitin: 13.6% of wild-type (Table II). (trilla1999chs7panew media 93a4edff)
- CSIII activity: 14.6% of wild-type (Table II). (trilla1999chs7panew media 93a4edff)
These quantitative data support the central functional claim that CHS7 is required for normal Chs3/CSIII-dependent chitin deposition. (trilla1999chs7panew pages 4-5)
Trilla et al. also show that balanced expression matters: co-overexpression of CHS3 and CHS7 increased total CSIII ~4-fold but basal activity only ~1.3-fold, consistent with Chs7 controlling a bottleneck that affects the pool of export-competent Chs3. (trilla1999chs7panew pages 7-8)
Lesage et al. (2005) quantified the genetic interaction landscape:
- Total network: 316 interactions among 163 genes. (lesage2005aninteractionalnetwork pages 1-2)
- CSIII subnetwork: 123 genes / 259 interactions. (lesage2005aninteractionalnetwork pages 2-4)
- CHS7 connectivity in this dataset: 31 genetic connections. (lesage2005aninteractionalnetwork pages 1-2)
These statistics indicate CHS7 is embedded in a dense neighborhood enriched for cell wall assembly and polarized secretion buffering, consistent with its key role in Chs3 trafficking. (lesage2005aninteractionalnetwork pages 1-2, lesage2005aninteractionalnetwork pages 2-4)
Microscopy and biochemical fractionation in Trilla et al. provide direct visual evidence that:
- Chs7 localizes to the ER/nuclear periphery. (trilla1999chs7panew media 93a4edff)
- In chs7Δ mutants, Chs3 is retained in the ER with perinuclear staining. (trilla1999chs7panew media afaeb15d)
These visual panels support the mechanistic model of CHS7 as an ER export factor for Chs3. (trilla1999chs7panew pages 6-7, trilla1999chs7panew pages 5-6)
The following table consolidates identity, function, localization, mechanism, interactions, and quantitative phenotypes with DOI URLs.
| Aspect | Key findings | Evidence/citation |
|---|---|---|
| Identity / verified target | - CHS7 = YHR142W in Saccharomyces cerevisiae; matches UniProt P38843 target context - Encodes a 316-aa, small multipass membrane protein with 6–7 predicted transmembrane segments - Classic primary literature identifies it as a factor specifically required for Chs3/CSIII regulation rather than general secretion |
Trilla 1999, J Cell Biol, doi: https://doi.org/10.1083/jcb.145.6.1153 (trilla1999chs7panew pages 4-5, trilla1999chs7panew pages 5-6, trilla1999chs7panew pages 1-2) |
| Subcellular localization | - Chs7p localizes mainly to the endoplasmic reticulum, including nuclear periphery / perinuclear ER and ER-associated patches - Colocalizes biochemically with Sec63p ER fractions - Later work suggests Chs7 can also co-traffic with Chs3 beyond the ER to bud neck / intracellular puncta |
Trilla 1999, doi: https://doi.org/10.1083/jcb.145.6.1153; Dharwada 2016, doi: https://doi.org/10.14288/1.0166170 (trilla1999chs7panew pages 6-7, trilla1999chs7panew pages 5-6, dharwada2016intracellulartraffickingof pages 40-45, trilla1999chs7panew media 93a4edff) |
| Primary function | - Chs7 is a client-specific export chaperone / escort for the major chitin synthase Chs3 - Required for ER exit of Chs3 and thereby for chitin synthase III (CSIII) function and normal wall chitin deposition - Does not broadly affect other secretory cargoes, CSI, or CSII |
Trilla 1999, doi: https://doi.org/10.1083/jcb.145.6.1153; Sánchez & Roncero 2022, doi: https://doi.org/10.3390/ijms232012251 (trilla1999chs7panew pages 6-7, trilla1999chs7panew pages 5-6, trilla1999chs7panew pages 1-2, sanchez2022chitinsynthesisin pages 3-4) |
| Client protein(s) / pathway context | - Principal documented client is Chs3, the synthase responsible for ~90–95% of cellular chitin in budding yeast - Chs7 acts in the early secretory pathway, upstream of Chs5/Chs6 exomer-mediated Golgi/TGN export - Chs3 retention in chs7Δ places CHS7 at the ER-exit/folding step of the trafficking itinerary |
Trilla 1999, doi: https://doi.org/10.1083/jcb.145.6.1153; Sánchez & Roncero 2022, doi: https://doi.org/10.3390/ijms232012251 (trilla1999chs7panew pages 1-2, sanchez2022chitinsynthesisin pages 3-4, lesage2005aninteractionalnetwork pages 1-2) |
| Mechanism / quality control | - In chs7Δ, Chs3 remains in the ER and can show punctate perinuclear signal consistent with aggregation - Review and 2023 QC work support that Chs7 prevents aggregation, helps load functional Chs3 into COPII vesicles, and masks cytosolic degrons that would otherwise trigger Doa10/ERAD-C - Chs3 molecules escaping canonical ERAD can also be cleared by INMAD/Asi pathways; luminal glycosylation protects against Hrd1/ERAD-L |
Trilla 1999, doi: https://doi.org/10.1083/jcb.145.6.1153; Sánchez & Roncero 2022, doi: https://doi.org/10.3390/ijms232012251; Sanchez et al. 2023, doi: https://doi.org/10.1091/mbc.e23-05-0186 (trilla1999chs7panew pages 6-7, sanchez2022chitinsynthesisin pages 4-6, sanchez2023multiplequalitycontrol pages 4-6, sanchez2023multiplequalitycontrol pages 13-15, sanchez2023multiplequalitycontrol pages 11-13, sanchez2023multiplequalitycontrol pages 1-2, sanchez2023multiplequalitycontrol pages 9-11) |
| Physical/functional partners | - Strongest supported partner is Chs3; co-immunoprecipitation and complex migration support a stable Chs3–Chs7 complex - Additional pathway factors discussed around Chs7-dependent trafficking include Erv14 (cargo receptor), Pfa4 (palmitoylation), Chs5/Chs6 (exomer export), Rer1/Erv46 (Golgi retrieval/QC), Chs4/Bni4 (activation/retention) - Chs7 colocalizes with Sec63p as an ER marker rather than as a client |
Dharwada 2016, doi: https://doi.org/10.14288/1.0166170; Sánchez & Roncero 2022, doi: https://doi.org/10.3390/ijms232012251; Trilla 1999, doi: https://doi.org/10.1083/jcb.145.6.1153 (trilla1999chs7panew pages 5-6, sanchez2022chitinsynthesisin pages 4-6, dharwada2016intracellulartraffickingof pages 50-54, dharwada2016intracellulartraffickingof pages 40-45, dharwada2016intracellulartraffickingof pages 81-84) |
| Quantitative phenotypes | - chs7 null cell wall chitin: 13.6% of WT - CSIII activity in chs7 null: 14.6% of WT - Joint CHS3 + CHS7 overexpression increased total CSIII ~4-fold, while basal activity increased only ~1.3-fold; adding CHS3 + CHS4 + CHS7 gave ~68 ± 11% more chitin than WT |
Trilla 1999, doi: https://doi.org/10.1083/jcb.145.6.1153 (trilla1999chs7panew pages 4-5, trilla1999chs7panew pages 6-7, trilla1999chs7panew pages 7-8, trilla1999chs7panew media 93a4edff) |
| Cellular / developmental phenotypes | - Calcofluor resistance at 1 mg/mL and failure to enlarge septa upon Calcofluor treatment - Reduced mating efficiency similar to chs3 mutants - Defects in ascospore wall maturation, including compact ascospores / loss of normal chitosan layer |
Trilla 1999, doi: https://doi.org/10.1083/jcb.145.6.1153 (trilla1999chs7panew pages 4-5, trilla1999chs7panew pages 1-2) |
| Regulation of CHS7 expression | - CHS7 transcript rises under conditions of elevated chitin demand - Reported induction: ~3.5× by α-factor, ~2× by Calcofluor, ~24× during sporulation - Supports interpretation that CHS7 availability can be rate-limiting for Chs3 export / CSIII output |
Trilla 1999, doi: https://doi.org/10.1083/jcb.145.6.1153 (trilla1999chs7panew pages 4-5, trilla1999chs7panew pages 8-10) |
| Genetic interaction network | - In SGA/network analysis, CHS7 had 31 genetic connections - Overall network: 316 interactions among 163 genes; CSIII-focused subnetwork: 123 genes / 259 interactions - CHS3/4/5/6/7/BNI4 form a dense neighborhood tied to cell wall assembly and polarized secretion |
Lesage 2005, BMC Genetics, doi: https://doi.org/10.1186/1471-2156-6-8 (lesage2005aninteractionalnetwork pages 2-4, lesage2005aninteractionalnetwork pages 1-2, lesage2005aninteractionalnetwork pages 4-5) |
| Key experimental approaches | - Functional HA/GFP tagging, complementation of Calcofluor phenotype, fluorescence microscopy, ER colocalization, fractionation, glycosidase sensitivity, and CSIII/chitin assays established the original model - Later work used co-IP, BN-PAGE, crosslinking, BiFC/split-YFP, protease accessibility, and cycloheximide chase - 2023 QC studies added MG-132, tandem fluorescent timer (tFT) SGA screens, and ERAD/INMAD mutant analysis |
Trilla 1999, doi: https://doi.org/10.1083/jcb.145.6.1153; Dharwada 2016, doi: https://doi.org/10.14288/1.0166170; Sanchez et al. 2023, doi: https://doi.org/10.1091/mbc.e23-05-0186 (trilla1999chs7panew pages 4-5, sanchez2023multiplequalitycontrol pages 4-6, sanchez2023multiplequalitycontrol pages 9-11, dharwada2016intracellulartraffickingof pages 50-54, dharwada2016intracellulartraffickingof pages 40-45) |
| Recent developments (2022–2023) | - 2022 review reframed Chs3/Chs7 as a paradigm for trafficking of multipass membrane proteins in yeast - 2023 work showed multiple layered QC mechanisms monitor Chs3 in the ER, with Chs7 specifically shielding Chs3 from ERAD-C - Emerging consensus: Chs7 is more than a passive escort; it contributes to proteostasis and productive trafficking of a complex membrane enzyme |
Sánchez & Roncero 2022, doi: https://doi.org/10.3390/ijms232012251; Sanchez et al. 2023, doi: https://doi.org/10.1091/mbc.e23-05-0186 (sanchez2022chitinsynthesisin pages 4-6, sanchez2023multiplequalitycontrol pages 4-6, sanchez2023multiplequalitycontrol pages 13-15, sanchez2023multiplequalitycontrol pages 11-13, sanchez2023multiplequalitycontrol pages 1-2) |
| Real-world / applications relevance | - CHS7 itself is not an enzyme target, but it is central to the biogenesis of the major fungal chitin synthase, linking it to cell wall robustness - Because fungal chitin synthesis is an antifungal-relevant pathway, Chs7/Chs3 trafficking is used as a model system for membrane-protein trafficking and fungal cell-wall control - Comparative fungal studies treat Chs7 as a Shr3-like export chaperone paradigm for chitin synthase trafficking beyond budding yeast |
Sánchez & Roncero 2022, doi: https://doi.org/10.3390/ijms232012251; González-Téllez & Riquelme 2025, doi: https://doi.org/10.3389/ffunb.2024.1505388 (sanchez2022chitinsynthesisin pages 4-6, gonzaleztellez2025cse8afilamentous pages 1-2) |
Table: This table condenses the core experimentally supported knowledge on Saccharomyces cerevisiae CHS7/YHR142W, including identity verification, localization, mechanism, quantitative phenotypes, network context, and recent quality-control insights. It is designed as a citation-ready reference for a gene function report.
References
(trilla1999chs7panew pages 4-5): J. A. Trilla, Á. Durán, and C. Roncero. Chs7p, a new protein involved in the control of protein export from the endoplasmic reticulum that is specifically engaged in the regulation of chitin synthesis in saccharomyces cerevisiae. The Journal of Cell Biology, 145:1153-1163, Jun 1999. URL: https://doi.org/10.1083/jcb.145.6.1153, doi:10.1083/jcb.145.6.1153. This article has 199 citations.
(sanchez2022chitinsynthesisin pages 4-6): Noelia Sánchez and César Roncero. Chitin synthesis in yeast: a matter of trafficking. International Journal of Molecular Sciences, 23:12251, Oct 2022. URL: https://doi.org/10.3390/ijms232012251, doi:10.3390/ijms232012251. This article has 21 citations.
(sanchez2023multiplequalitycontrol pages 4-6): Noelia Sanchez, Nagore de Leon, Rosario Valle, Jia Jun Fung, Anton Khmelinskii, and Cesar Roncero. Multiple quality control mechanisms monitor yeast chitin synthase folding in the endoplasmic reticulum. Molecular Biology of the Cell, Dec 2023. URL: https://doi.org/10.1091/mbc.e23-05-0186, doi:10.1091/mbc.e23-05-0186. This article has 3 citations and is from a domain leading peer-reviewed journal.
(trilla1999chs7panew pages 5-6): J. A. Trilla, Á. Durán, and C. Roncero. Chs7p, a new protein involved in the control of protein export from the endoplasmic reticulum that is specifically engaged in the regulation of chitin synthesis in saccharomyces cerevisiae. The Journal of Cell Biology, 145:1153-1163, Jun 1999. URL: https://doi.org/10.1083/jcb.145.6.1153, doi:10.1083/jcb.145.6.1153. This article has 199 citations.
(sanchez2022chitinsynthesisin pages 3-4): Noelia Sánchez and César Roncero. Chitin synthesis in yeast: a matter of trafficking. International Journal of Molecular Sciences, 23:12251, Oct 2022. URL: https://doi.org/10.3390/ijms232012251, doi:10.3390/ijms232012251. This article has 21 citations.
(trilla1999chs7panew pages 6-7): J. A. Trilla, Á. Durán, and C. Roncero. Chs7p, a new protein involved in the control of protein export from the endoplasmic reticulum that is specifically engaged in the regulation of chitin synthesis in saccharomyces cerevisiae. The Journal of Cell Biology, 145:1153-1163, Jun 1999. URL: https://doi.org/10.1083/jcb.145.6.1153, doi:10.1083/jcb.145.6.1153. This article has 199 citations.
(trilla1999chs7panew media afaeb15d): J. A. Trilla, Á. Durán, and C. Roncero. Chs7p, a new protein involved in the control of protein export from the endoplasmic reticulum that is specifically engaged in the regulation of chitin synthesis in saccharomyces cerevisiae. The Journal of Cell Biology, 145:1153-1163, Jun 1999. URL: https://doi.org/10.1083/jcb.145.6.1153, doi:10.1083/jcb.145.6.1153. This article has 199 citations.
(trilla1999chs7panew pages 7-8): J. A. Trilla, Á. Durán, and C. Roncero. Chs7p, a new protein involved in the control of protein export from the endoplasmic reticulum that is specifically engaged in the regulation of chitin synthesis in saccharomyces cerevisiae. The Journal of Cell Biology, 145:1153-1163, Jun 1999. URL: https://doi.org/10.1083/jcb.145.6.1153, doi:10.1083/jcb.145.6.1153. This article has 199 citations.
(trilla1999chs7panew media 93a4edff): J. A. Trilla, Á. Durán, and C. Roncero. Chs7p, a new protein involved in the control of protein export from the endoplasmic reticulum that is specifically engaged in the regulation of chitin synthesis in saccharomyces cerevisiae. The Journal of Cell Biology, 145:1153-1163, Jun 1999. URL: https://doi.org/10.1083/jcb.145.6.1153, doi:10.1083/jcb.145.6.1153. This article has 199 citations.
(dharwada2016intracellulartraffickingof pages 40-45): Sai Tejasvi Dharwada. Intracellular trafficking of a model polytopic membrane protein in saccharomyces cerevisiae. ArXiv, Jan 2016. URL: https://doi.org/10.14288/1.0166170, doi:10.14288/1.0166170. This article has 0 citations.
(dharwada2016intracellulartraffickingof pages 50-54): Sai Tejasvi Dharwada. Intracellular trafficking of a model polytopic membrane protein in saccharomyces cerevisiae. ArXiv, Jan 2016. URL: https://doi.org/10.14288/1.0166170, doi:10.14288/1.0166170. This article has 0 citations.
(lesage2005aninteractionalnetwork pages 1-2): Guillaume Lesage, Jesse Shapiro, Charles A Specht, Anne-Marie Sdicu, Patrice Ménard, Shamiza Hussein, Amy Hin Yan Tong, Charles Boone, and Howard Bussey. An interactional network of genes involved in chitin synthesis in saccharomyces cerevisiae. BMC Genetics, 6:8-8, Feb 2005. URL: https://doi.org/10.1186/1471-2156-6-8, doi:10.1186/1471-2156-6-8. This article has 151 citations.
(sanchez2023multiplequalitycontrol pages 11-13): Noelia Sanchez, Nagore de Leon, Rosario Valle, Jia Jun Fung, Anton Khmelinskii, and Cesar Roncero. Multiple quality control mechanisms monitor yeast chitin synthase folding in the endoplasmic reticulum. Molecular Biology of the Cell, Dec 2023. URL: https://doi.org/10.1091/mbc.e23-05-0186, doi:10.1091/mbc.e23-05-0186. This article has 3 citations and is from a domain leading peer-reviewed journal.
(sanchez2023multiplequalitycontrol pages 9-11): Noelia Sanchez, Nagore de Leon, Rosario Valle, Jia Jun Fung, Anton Khmelinskii, and Cesar Roncero. Multiple quality control mechanisms monitor yeast chitin synthase folding in the endoplasmic reticulum. Molecular Biology of the Cell, Dec 2023. URL: https://doi.org/10.1091/mbc.e23-05-0186, doi:10.1091/mbc.e23-05-0186. This article has 3 citations and is from a domain leading peer-reviewed journal.
(sanchez2023multiplequalitycontrol pages 13-15): Noelia Sanchez, Nagore de Leon, Rosario Valle, Jia Jun Fung, Anton Khmelinskii, and Cesar Roncero. Multiple quality control mechanisms monitor yeast chitin synthase folding in the endoplasmic reticulum. Molecular Biology of the Cell, Dec 2023. URL: https://doi.org/10.1091/mbc.e23-05-0186, doi:10.1091/mbc.e23-05-0186. This article has 3 citations and is from a domain leading peer-reviewed journal.
(sanchez2023multiplequalitycontrol pages 1-2): Noelia Sanchez, Nagore de Leon, Rosario Valle, Jia Jun Fung, Anton Khmelinskii, and Cesar Roncero. Multiple quality control mechanisms monitor yeast chitin synthase folding in the endoplasmic reticulum. Molecular Biology of the Cell, Dec 2023. URL: https://doi.org/10.1091/mbc.e23-05-0186, doi:10.1091/mbc.e23-05-0186. This article has 3 citations and is from a domain leading peer-reviewed journal.
(lesage2005aninteractionalnetwork pages 2-4): Guillaume Lesage, Jesse Shapiro, Charles A Specht, Anne-Marie Sdicu, Patrice Ménard, Shamiza Hussein, Amy Hin Yan Tong, Charles Boone, and Howard Bussey. An interactional network of genes involved in chitin synthesis in saccharomyces cerevisiae. BMC Genetics, 6:8-8, Feb 2005. URL: https://doi.org/10.1186/1471-2156-6-8, doi:10.1186/1471-2156-6-8. This article has 151 citations.
(trilla1999chs7panew pages 1-2): J. A. Trilla, Á. Durán, and C. Roncero. Chs7p, a new protein involved in the control of protein export from the endoplasmic reticulum that is specifically engaged in the regulation of chitin synthesis in saccharomyces cerevisiae. The Journal of Cell Biology, 145:1153-1163, Jun 1999. URL: https://doi.org/10.1083/jcb.145.6.1153, doi:10.1083/jcb.145.6.1153. This article has 199 citations.
(dharwada2016intracellulartraffickingof pages 81-84): Sai Tejasvi Dharwada. Intracellular trafficking of a model polytopic membrane protein in saccharomyces cerevisiae. ArXiv, Jan 2016. URL: https://doi.org/10.14288/1.0166170, doi:10.14288/1.0166170. This article has 0 citations.
(trilla1999chs7panew pages 8-10): J. A. Trilla, Á. Durán, and C. Roncero. Chs7p, a new protein involved in the control of protein export from the endoplasmic reticulum that is specifically engaged in the regulation of chitin synthesis in saccharomyces cerevisiae. The Journal of Cell Biology, 145:1153-1163, Jun 1999. URL: https://doi.org/10.1083/jcb.145.6.1153, doi:10.1083/jcb.145.6.1153. This article has 199 citations.
(lesage2005aninteractionalnetwork pages 4-5): Guillaume Lesage, Jesse Shapiro, Charles A Specht, Anne-Marie Sdicu, Patrice Ménard, Shamiza Hussein, Amy Hin Yan Tong, Charles Boone, and Howard Bussey. An interactional network of genes involved in chitin synthesis in saccharomyces cerevisiae. BMC Genetics, 6:8-8, Feb 2005. URL: https://doi.org/10.1186/1471-2156-6-8, doi:10.1186/1471-2156-6-8. This article has 151 citations.
(gonzaleztellez2025cse8afilamentous pages 1-2): Samantha Verónica González-Téllez and Meritxell Riquelme. Cse-8, a filamentous fungus-specific shr3-like chaperone, facilitates endoplasmic reticulum exit of chitin synthase chs-3 (class i) in neurospora crassa. Frontiers in Fungal Biology, Jan 2025. URL: https://doi.org/10.3389/ffunb.2024.1505388, doi:10.3389/ffunb.2024.1505388. This article has 6 citations.
id: P38843
gene_symbol: CHS7
product_type: PROTEIN
status: COMPLETE
taxon:
id: NCBITaxon:559292
label: Saccharomyces cerevisiae
description: 'CHS7 encodes an endoplasmic-reticulum membrane export chaperone for the chitin synthase Chs3, promoting Chs3
folding/proteostasis, ER-to-Golgi export, and normal chitin synthase III-dependent cell wall chitin deposition.'
existing_annotations:
- term:
id: GO:0006031
label: chitin biosynthetic process
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: 'chitin biosynthetic process reviewed for CHS7: ACCEPT.'
action: ACCEPT
reason: Retain as a core biological-process consequence of Chs7-dependent Chs3 maturation and export; loss of CHS7
strongly reduces chitin synthase III output and cell wall chitin deposition.
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: Loss of CHS7 causes **ER retention of Chs3**, severe reduction of **cell wall chitin** and **CSIII
activity**
- term:
id: GO:0005789
label: endoplasmic reticulum membrane
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: 'endoplasmic reticulum membrane reviewed for CHS7: ACCEPT.'
action: ACCEPT
reason: Retain as the best-supported cellular location; Chs7 is a multipass ER membrane protein acting at the Chs3
ER export step.
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: functional tagged Chs7 showed **perinuclear/ER localization** and co-localization with the ER marker
Sec63p
- term:
id: GO:0006457
label: protein folding
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: 'protein folding reviewed for CHS7: ACCEPT.'
action: ACCEPT
reason: Retain because Chs7 functions in client folding/proteostasis of the polytopic Chs3 cargo, even though the
more specific role is a dedicated export chaperone.
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: describe Chs7 as a **specific ER chaperone** that prevents Chs3 aggregation and promotes ER exit via
**COPII loading**
- term:
id: GO:0051082
label: unfolded protein binding
evidence_type: IBA
original_reference_id: GO_REF:0000033
review:
summary: 'unfolded protein binding reviewed for CHS7: MODIFY.'
action: MODIFY
reason: The generic unfolded-protein binding term is less informative than the supported Chs3-specific
chaperone/escort role; replace with protein folding chaperone.
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: Chs7 is an export chaperone in the sense that **Chs3 ER exit depends on Chs7**
proposed_replacement_terms:
- id: GO:0044183
label: protein folding chaperone
- term:
id: GO:0005789
label: endoplasmic reticulum membrane
evidence_type: IEA
original_reference_id: GO_REF:0000044
review:
summary: 'endoplasmic reticulum membrane reviewed for CHS7: ACCEPT.'
action: ACCEPT
reason: Retain as the best-supported cellular location; Chs7 is a multipass ER membrane protein acting at the Chs3
ER export step.
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: functional tagged Chs7 showed **perinuclear/ER localization** and co-localization with the ER marker
Sec63p
- term:
id: GO:0015031
label: protein transport
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: 'protein transport reviewed for CHS7: MODIFY.'
action: MODIFY
reason: General protein transport is too broad for the curated evidence; Chs7 specifically promotes Chs3 exit from
the ER toward the Golgi.
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: Chs7 is required for exit of Chs3 from the ER
proposed_replacement_terms:
- id: GO:0006888
label: endoplasmic reticulum to Golgi vesicle-mediated transport
- term:
id: GO:0071555
label: cell wall organization
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: 'cell wall organization reviewed for CHS7: KEEP_AS_NON_CORE.'
action: KEEP_AS_NON_CORE
reason: Keep as a valid downstream phenotype of impaired Chs3-dependent chitin deposition, but not the direct
molecular role of Chs7.
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: These quantitative data support the central functional claim that CHS7 is required for normal
Chs3/CSIII-dependent chitin deposition
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:18467557
review:
summary: 'protein binding reviewed for CHS7: MARK_AS_OVER_ANNOTATED.'
action: MARK_AS_OVER_ANNOTATED
reason: Protein binding is too generic; the Chs3 interaction is better captured by a specific chaperone/export role.
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: Chs7 **physically interacts** with full-length Chs3 and certain truncated Chs3 forms
- term:
id: GO:0005515
label: protein binding
evidence_type: IPI
original_reference_id: PMID:37968396
review:
summary: 'protein binding reviewed for CHS7: MARK_AS_OVER_ANNOTATED.'
action: MARK_AS_OVER_ANNOTATED
reason: Protein binding is too generic; the Chs3 interaction is better captured by a specific chaperone/export role.
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: Chs7 **physically interacts** with full-length Chs3 and certain truncated Chs3 forms
- term:
id: GO:0005783
label: endoplasmic reticulum
evidence_type: HDA
original_reference_id: PMID:22842922
review:
summary: 'endoplasmic reticulum reviewed for CHS7: ACCEPT.'
action: ACCEPT
reason: Retain as a supported broader ER localization, consistent with the more precise ER membrane annotation.
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: functional tagged Chs7 showed **perinuclear/ER localization** and co-localization with the ER marker
Sec63p
- term:
id: GO:0005783
label: endoplasmic reticulum
evidence_type: HDA
original_reference_id: PMID:26928762
review:
summary: 'endoplasmic reticulum reviewed for CHS7: ACCEPT.'
action: ACCEPT
reason: Retain as a supported broader ER localization, consistent with the more precise ER membrane annotation.
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: functional tagged Chs7 showed **perinuclear/ER localization** and co-localization with the ER marker
Sec63p
- term:
id: GO:0005934
label: cellular bud tip
evidence_type: HDA
original_reference_id: PMID:22842922
review:
summary: 'cellular bud tip reviewed for CHS7: KEEP_AS_NON_CORE.'
action: KEEP_AS_NON_CORE
reason: Keep as context-dependent localization associated with Chs3/chitin deposition biology, not as the primary
site of Chs7 action.
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: Chs7 can also **exit the ER with Chs3** and co-localize with Chs3 at the bud neck and intracellular
puncta
- term:
id: GO:0005935
label: cellular bud neck
evidence_type: HDA
original_reference_id: PMID:22842922
review:
summary: 'cellular bud neck reviewed for CHS7: KEEP_AS_NON_CORE.'
action: KEEP_AS_NON_CORE
reason: Keep as context-dependent bud-neck localization associated with chitin deposition, not as the core ER export
role.
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: Chs7 can also **exit the ER with Chs3** and co-localize with Chs3 at the bud neck and intracellular
puncta
- term:
id: GO:0005628
label: prospore membrane
evidence_type: HDA
original_reference_id: PMID:24390141
review:
summary: 'prospore membrane reviewed for CHS7: KEEP_AS_NON_CORE.'
action: KEEP_AS_NON_CORE
reason: Keep as a sporulation-context localization observation, peripheral to the core ER chaperone/export function.
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: Reported induction includes **~24-fold during sporulation**
- term:
id: GO:0005935
label: cellular bud neck
evidence_type: IDA
original_reference_id: PMID:29405545
review:
summary: 'cellular bud neck reviewed for CHS7: KEEP_AS_NON_CORE.'
action: KEEP_AS_NON_CORE
reason: Keep as context-dependent bud-neck localization associated with chitin deposition, not as the core ER export
role.
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: Chs7 can also **exit the ER with Chs3** and co-localize with Chs3 at the bud neck and intracellular
puncta
- term:
id: GO:0005789
label: endoplasmic reticulum membrane
evidence_type: IDA
original_reference_id: PMID:10366589
review:
summary: 'endoplasmic reticulum membrane reviewed for CHS7: ACCEPT.'
action: ACCEPT
reason: Retain as the best-supported cellular location; Chs7 is a multipass ER membrane protein acting at the Chs3
ER export step.
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: functional tagged Chs7 showed **perinuclear/ER localization** and co-localization with the ER marker
Sec63p
- term:
id: GO:0006031
label: chitin biosynthetic process
evidence_type: IMP
original_reference_id: PMID:10366589
review:
summary: 'chitin biosynthetic process reviewed for CHS7: ACCEPT.'
action: ACCEPT
reason: Retain as a core biological-process consequence of Chs7-dependent Chs3 maturation and export; loss of CHS7
strongly reduces chitin synthase III output and cell wall chitin deposition.
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: Loss of CHS7 causes **ER retention of Chs3**, severe reduction of **cell wall chitin** and **CSIII
activity**
- term:
id: GO:0006457
label: protein folding
evidence_type: IMP
original_reference_id: PMID:15623581
review:
summary: 'protein folding reviewed for CHS7: ACCEPT.'
action: ACCEPT
reason: Retain because Chs7 functions in client folding/proteostasis of the polytopic Chs3 cargo, even though the
more specific role is a dedicated export chaperone.
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: describe Chs7 as a **specific ER chaperone** that prevents Chs3 aggregation and promotes ER exit via
**COPII loading**
- term:
id: GO:0006888
label: endoplasmic reticulum to Golgi vesicle-mediated transport
evidence_type: IDA
original_reference_id: PMID:10366589
review:
summary: 'endoplasmic reticulum to Golgi vesicle-mediated transport reviewed for CHS7: ACCEPT.'
action: ACCEPT
reason: 'Retain as a core process: the strongest mechanistic evidence places Chs7 at Chs3 ER exit and ER-to-Golgi trafficking.'
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: Chs7 is an export chaperone in the sense that **Chs3 ER exit depends on Chs7**
- term:
id: GO:0051082
label: unfolded protein binding
evidence_type: IMP
original_reference_id: PMID:15623581
review:
summary: 'unfolded protein binding reviewed for CHS7: MODIFY.'
action: MODIFY
reason: The generic unfolded-protein binding term is less informative than the supported Chs3-specific
chaperone/escort role; replace with protein folding chaperone.
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: describe Chs7 as a **specific ER chaperone** that prevents Chs3 aggregation and promotes ER exit via
**COPII loading**
proposed_replacement_terms:
- id: GO:0044183
label: protein folding chaperone
references:
- id: GO_REF:0000033
title: Annotation inferences using phylogenetic trees
findings: []
- id: GO_REF:0000043
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
findings: []
- id: GO_REF:0000044
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by
conservative changes to GO terms applied by UniProt
findings: []
- id: PMID:10366589
title: Chs7p, a new protein involved in the control of protein export from the endoplasmic reticulum that is
specifically engaged in the regulation of chitin synthesis in Saccharomyces cerevisiae.
findings: []
- id: PMID:15623581
title: Specialized membrane-localized chaperones prevent aggregation of polytopic proteins in the ER.
findings: []
- id: PMID:18467557
title: An in vivo map of the yeast protein interactome.
findings: []
- id: PMID:22842922
title: Dissecting DNA damage response pathways by analysing protein localization and abundance changes during DNA
replication stress.
findings: []
- id: PMID:24390141
title: A visual screen of protein localization during sporulation identifies new components of prospore
membrane-associated complexes in budding yeast.
findings: []
- id: PMID:26928762
title: 'One library to make them all: streamlining the creation of yeast libraries via a SWAp-Tag strategy.'
findings: []
- id: PMID:29405545
title: The chaperone Chs7 forms a stable complex with Chs3 and promotes its activity at the cell surface.
findings: []
- id: PMID:37968396
title: The social and structural architecture of the yeast protein interactome.
findings: []
- id: file:yeast/CHS7/CHS7-deep-research-falcon.md
title: Falcon deep research report for yeast CHS7
findings: []
- id: file:interpro/panther/PTHR35329/PTHR35329-metadata.yaml
title: PANTHER family PTHR35329, Chitin synthase export chaperone
findings: []
core_functions:
- description: Chs7 acts as a client-specific ER membrane chaperone/escort for Chs3, licensing productive Chs3
biogenesis and export rather than acting as the chitin synthase enzyme itself.
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: Chs7 acts at the earliest licensing step for the Chs3 trafficking itinerary
molecular_function:
id: GO:0044183
label: protein folding chaperone
directly_involved_in:
- id: GO:0006888
label: endoplasmic reticulum to Golgi vesicle-mediated transport
- id: GO:0006031
label: chitin biosynthetic process
locations:
- id: GO:0005789
label: endoplasmic reticulum membrane
proposed_new_terms:
- proposed_name: chitin synthase export chaperone activity
proposed_definition: A protein folding chaperone activity that binds or escorts a chitin synthase client in the
endoplasmic reticulum to promote its productive folding, ER quality-control evasion, and export toward the Golgi.
justification: Chs7 is not a generic unfolded-protein binder; the yeast evidence supports a dedicated export-chaperone
activity for Chs3/chitin synthase III that is more specific than existing chaperone terms. The 2023 Sanchez et al.
MBoC study strengthens this by showing that Chs7 also functions as a degron shield, masking Chs3 cytosolic degrons
to prevent ERAD-C targeting.
proposed_parent:
id: GO:0044183
label: protein folding chaperone
supported_by:
- reference_id: file:yeast/CHS7/CHS7-deep-research-falcon.md
supporting_text: dedicated chaperones like Chs7 can simultaneously function as **folding/escort factors and degron
shields**
suggested_questions:
- question: Does Chs7 have physiologically important clients other than Chs3, or is its conserved role essentially
dedicated to chitin synthase export?
experts: []
- question: Which Chs3 surfaces are shielded by Chs7 during ER quality control and ERAD avoidance?
experts: []
suggested_experiments:
- hypothesis: Chs7 promotes Chs3 ER export by masking Chs3 degrons while maintaining an export-competent conformation.
description: Map Chs3 regions that require Chs7 using endogenous tagged Chs3 truncation or degron mutants, ER export
assays, co-immunoprecipitation, and ERAD/INMAD pathway perturbations.
experiment_type: client-mapping and trafficking assay