Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0005515 protein binding	IPI PMID:16429126 Proteome survey reveals modularity of the yeast cell machine...	MARK AS OVER ANNOTATED	Summary: Protein binding is true but too generic for Sqt1. The biologically informative interaction is client-specific binding to Rpl10 as a dedicated ribosomal-protein carrier chaperone. Reason: GO:0005515 does not capture the direction, specificity, or functional consequence of Sqt1-Rpl10 binding. The core molecular function is better represented by GO:0140597 protein carrier chaperone, supported directly by PMID:26112308. Supporting Evidence: PMID:26112308 Affinity purification of four chaperones (Rrb1, Syo1, Sqt1 and Yar1) selectively enriched the mRNAs encoding their specific ribosomal protein clients (Rpl3, Rpl5, Rpl10 and Rps3).
GO:0005515 protein binding	IPI PMID:16554755 Global landscape of protein complexes in the yeast Saccharom...	MARK AS OVER ANNOTATED	Summary: High-throughput complex data support physical association, but GO:0005515 is a vague annotation that does not express Sqt1's specific Rpl10 carrier chaperone function. Reason: Retaining generic protein binding would obscure the curated function: Sqt1 binds Rpl10 as a dedicated ribosomal-protein chaperone during 60S subunit maturation. Supporting Evidence: PMID:26112308 X-ray crystallography reveals how the N-terminal, rRNA-binding residues of Rpl10 are shielded by Sqt1's WD-repeat beta-propeller, providing mechanistic insight into the incorporation of Rpl10 into pre-60S subunits.
GO:0005515 protein binding	IPI PMID:27107014 An inter-species protein-protein interaction network across ...	MARK AS OVER ANNOTATED	Summary: Inter-species high-throughput protein binding observations are not a good basis for a yeast SQT1 core function annotation. Reason: The reported cross-species interactors do not define Sqt1's yeast cellular role. SQT1 should be curated around experimentally supported Rpl10 carrier chaperone activity and 60S subunit assembly rather than generic protein binding. Supporting Evidence: file:yeast/SQT1/SQT1-deep-research-falcon.md Sqt1 is not an enzyme catalyzing a chemical transformation; instead, it is best described as a protein-folding/handling factor that binds Rpl10 and supports its productive assembly into late pre-60S particles.
GO:0005515 protein binding	IPI PMID:37968396 The social and structural architecture of the yeast protein ...	MARK AS OVER ANNOTATED	Summary: A large-scale interactome protein binding annotation is less informative than the mechanistic Sqt1-Rpl10 chaperone model. Reason: Generic protein binding should not be accepted as a core molecular function when a specific carrier chaperone activity for Rpl10 is supported by biochemical and structural evidence. Supporting Evidence: PMID:26112308 Co-translational capturing of nascent ribosomal proteins by dedicated chaperones constitutes an elegant mechanism to prevent unspecific interactions and aggregation of ribosomal proteins on their road to incorporation.
GO:0051082 unfolded protein binding	IDA PMID:26112308 Co-translational capturing of nascent ribosomal proteins by ...	MODIFY	Summary: The evidence from PMID:26112308 supports a dedicated Rpl10 carrier chaperone activity, not generic binding to unfolded proteins. Reason: Sqt1 binds the Rpl10 N-terminus with client specificity and shields aggregation-prone rRNA-binding residues before Rpl10 incorporation into pre-60S subunits. GO:0140597 protein carrier chaperone is the appropriate replacement. Proposed replacements: protein carrier chaperone Supporting Evidence: PMID:26112308 X-ray crystallography reveals how the N-terminal, rRNA-binding residues of Rpl10 are shielded by Sqt1's WD-repeat beta-propeller, providing mechanistic insight into the incorporation of Rpl10 into pre-60S subunits.
GO:0005737 cytoplasm	HDA PMID:11914276 Subcellular localization of the yeast proteome	ACCEPT	Summary: Cytoplasmic localization is consistent with Sqt1's role in co-translational Rpl10 capture and late cytoplasmic 60S maturation. Reason: The high-throughput cytoplasm annotation agrees with the mechanistic model and with the more specific cytosol annotation. Supporting Evidence: file:yeast/SQT1/SQT1-deep-research-falcon.md The combined evidence supports Sqt1 acting primarily in the cytoplasm, where late 60S maturation steps occur, including Rpl10 loading and Nmd3 release coordinated with Lsg1.
GO:0042273 ribosomal large subunit biogenesis	IMP PMID:26112308 Co-translational capturing of nascent ribosomal proteins by ...	ACCEPT	Summary: Sqt1 is a dedicated Rpl10 chaperone required for proper late 60S ribosomal subunit maturation. Reason: This process annotation accurately captures Sqt1's role in ribosomal large subunit biogenesis through client-specific Rpl10 handling. Supporting Evidence: PMID:26112308 X-ray crystallography reveals how the N-terminal, rRNA-binding residues of Rpl10 are shielded by Sqt1's WD-repeat β-propeller, providing mechanistic insight into the incorporation of Rpl10 into pre-60S subunits.
GO:0000027 ribosomal large subunit assembly	IMP PMID:9271392 SQT1, which encodes an essential WD domain protein of Saccha...	ACCEPT	Summary: The original SQT1 study showed half-mer polysome defects and reduced Qsr1 levels on free 60S subunits when SQT1 function was reduced, supporting a late 60S assembly function. Reason: This annotation remains correct and is strengthened by later evidence that Sqt1 chaperones Rpl10 for late pre-60S incorporation. Supporting Evidence: PMID:9271392 Loss of SQT1 function by down regulation from an inducible promoter results in formation of half-mer polyribosomes and decreased Qsr1p levels on free 60S subunits. Sqt1p thus appears to be involved in a late step of 60S subunit assembly or modification in the cytoplasm.
GO:0005829 cytosol	IDA PMID:9271392 SQT1, which encodes an essential WD domain protein of Saccha...	ACCEPT	Summary: Cytosolic localization is consistent with the original biochemical fractionation and with Sqt1's role in co-translational Rpl10 capture and late cytoplasmic 60S maturation. Reason: Cytosol is the best-supported core cellular location for Sqt1 function. Supporting Evidence: PMID:9271392 Sqt1p thus appears to be involved in a late step of 60S subunit assembly or modification in the cytoplasm.

Core Functions

Sqt1 is a dedicated cytosolic carrier chaperone for ribosomal protein Rpl10/uL16. It co-translationally recognizes the Rpl10 N-terminus, shields aggregation-prone rRNA-binding residues, and promotes Rpl10 incorporation during late cytoplasmic 60S ribosomal subunit maturation.

Molecular Function:

protein carrier chaperone

Directly Involved In:

ribosomal large subunit biogenesis ribosomal large subunit assembly

Cellular Locations:

cytosol

Supporting Evidence:

PMID:26112308
X-ray crystallography reveals how the N-terminal, rRNA-binding residues of Rpl10 are shielded by Sqt1's WD-repeat beta-propeller, providing mechanistic insight into the incorporation of Rpl10 into pre-60S subunits.
PMID:9271392
Sqt1p thus appears to be involved in a late step of 60S subunit assembly or modification in the cytoplasm.

References

PMID:11914276

Subcellular localization of the yeast proteome

PMID:16429126

Proteome survey reveals modularity of the yeast cell machinery

PMID:16554755

Global landscape of protein complexes in the yeast Saccharomyces cerevisiae

PMID:26112308

Co-translational capturing of nascent ribosomal proteins by their dedicated chaperones

Sqt1 is a dedicated chaperone for Rpl10 and shields Rpl10's N-terminal rRNA-binding residues during incorporation into pre-60S subunits.

"Affinity purification of four chaperones (Rrb1, Syo1, Sqt1 and Yar1) selectively enriched the mRNAs encoding their specific ribosomal protein clients (Rpl3, Rpl5, Rpl10 and Rps3). X-ray crystallography reveals how the N-terminal, rRNA-binding residues of Rpl10 are shielded by Sqt1's WD-repeat beta-propeller."

PMID:27107014

An inter-species protein-protein interaction network across vast evolutionary distance

PMID:37968396

The social and structural architecture of the yeast protein interactome

PMID:9271392

SQT1, which encodes an essential WD domain protein of Saccharomyces cerevisiae, suppresses dominant-negative mutations of the ribosomal protein gene QSR1

Sqt1 is required for late 60S subunit assembly or modification in the cytoplasm.

"Loss of SQT1 function by down regulation from an inducible promoter results in formation of half-mer polyribosomes and decreased Qsr1p levels on free 60S subunits."

file:yeast/SQT1/SQT1-deep-research-falcon.md

Falcon deep research report for SQT1

Falcon supports SQT1 as a cytosolic Rpl10 carrier chaperone required for late 60S maturation and ribosome homeostasis.

"Sqt1 is an essential cytoplasmic WD40-repeat beta-propeller protein that functions as a dedicated chaperone/escortin for ribosomal protein Rpl10/uL16."

Suggested Experiments

Experiment: Use separation-of-function SQT1 interface mutants to compare Rpl10 binding, Rpl10 solubility, 60S subunit maturation, and oxidative-stress repair in the same strain background.

Type: genetics

Experiment: Reconstitute Sqt1-mediated Rpl10 handoff to pre-60S particles with purified late maturation factors and measure dependence on Lsg1 and Nmd3 remodeling.

Type: biochemistry

Experiment: Validate high-throughput Sqt1 protein-binding partners by reciprocal co-immunoprecipitation and test whether any interactions change under ribosome assembly stress or oxidative stress.

Type: proteomics

📚 Additional Documentation

Deep Research Falcon

(SQT1-deep-research-falcon.md)

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organism_full: Saccharomyces cerevisiae (strain ATCC 204508 / S288c) (Baker's yeast).
protein_family: Not specified in UniProt
protein_domains: WD40/YVTN_repeat-like_dom_sf. (IPR015943); WD40_repeat_dom_sf.
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Question

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

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.

Target Gene/Protein Identity (from UniProt):

UniProt Accession: P35184
Protein Description: RecName: Full=Ribosome assembly protein SQT1;
Gene Information: Name=SQT1; OrderedLocusNames=YIR012W; ORFNames=YIB12W;
Organism (full): Saccharomyces cerevisiae (strain ATCC 204508 / S288c) (Baker's yeast).
Protein Family: Not specified in UniProt
Key Domains: WD40/YVTN_repeat-like_dom_sf. (IPR015943); WD40_repeat_dom_sf. (IPR036322); WD40_rpt. (IPR001680); WD_repeat_multifunction. (IPR051179); WD40 (PF00400)

MANDATORY VERIFICATION STEPS:

Check if the gene symbol "SQT1" matches the protein description above
Verify the organism is correct: Saccharomyces cerevisiae (strain ATCC 204508 / S288c) (Baker's yeast).
Check if protein family/domains align with what you find in literature
If you find literature for a DIFFERENT gene with the same or similar symbol, STOP

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'SQT1' 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

Research Target:

Please provide a comprehensive research report on the gene SQT1 (gene ID: SQT1, UniProt: P35184) 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.

Output

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.

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

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.

Target Gene/Protein Identity (from UniProt):

UniProt Accession: P35184
Protein Description: RecName: Full=Ribosome assembly protein SQT1;
Gene Information: Name=SQT1; OrderedLocusNames=YIR012W; ORFNames=YIB12W;
Organism (full): Saccharomyces cerevisiae (strain ATCC 204508 / S288c) (Baker's yeast).
Protein Family: Not specified in UniProt
Key Domains: WD40/YVTN_repeat-like_dom_sf. (IPR015943); WD40_repeat_dom_sf. (IPR036322); WD40_rpt. (IPR001680); WD_repeat_multifunction. (IPR051179); WD40 (PF00400)

MANDATORY VERIFICATION STEPS:

Check if the gene symbol "SQT1" matches the protein description above
Verify the organism is correct: Saccharomyces cerevisiae (strain ATCC 204508 / S288c) (Baker's yeast).
Check if protein family/domains align with what you find in literature
If you find literature for a DIFFERENT gene with the same or similar symbol, STOP

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'SQT1' 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

Research Target:

Please provide a comprehensive research report on the gene SQT1 (gene ID: SQT1, UniProt: P35184) 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.

Research Report: Functional Annotation of Saccharomyces cerevisiae SQT1 (UniProt P35184; YIR012W)

0) Target verification (mandatory)

The sources reviewed explicitly study Sqt1/SQT1/YIR012W in Saccharomyces cerevisiae as an essential ribosome assembly protein with an 8-bladed WD40 β-propeller that acts as a dedicated chaperone for ribosomal protein Rpl10 (uL16); this matches the UniProt description for accession P35184 and its WD40-repeat domain architecture. (pausch2015cotranslationalcapturingof pages 9-10, pillet2017holdonto pages 2-3, pausch2015cotranslationalcapturingof pages 4-5)

1) Key concepts and definitions (current understanding)

1.1 Dedicated ribosomal-protein (r-protein) chaperones

Yeast ribosome assembly requires safe handling of highly basic, aggregation-prone r-proteins before they are incorporated into pre-ribosomal particles. In addition to general ribosome-associated chaperones and importins, a subset of r-proteins rely on “dedicated chaperones” that bind specific r-protein clients to maintain solubility, prevent non-specific interactions, and coordinate delivery to assembly sites. (pillet2017holdonto pages 1-2, pillet2017holdonto pages 2-3)

Sqt1 is a canonical example: it is a dedicated chaperone whose client is Rpl10/uL16, a late-incorporating large-subunit r-protein. (pillet2017holdonto pages 2-3)

1.2 What Sqt1 is (and is not)

Sqt1 is not an enzyme catalyzing a chemical transformation; instead, it is best described as a protein-folding/handling factor (chaperone/escortin) that binds Rpl10 and supports its productive assembly into late pre-60S particles. (espinarmarchena2017placeholderfactorsin pages 12-13, pillet2017holdonto pages 2-3)

2) Molecular function of Sqt1: primary role and mechanism

2.1 Primary function: chaperoning and delivery of Rpl10/uL16 for late cytoplasmic 60S maturation

Multiple lines of genetic, biochemical, and structural evidence converge on the model that Sqt1’s essential role is to bind and chaperone Rpl10/uL16 and support its incorporation into maturing 60S subunits during late steps of ribosome biogenesis. (west2005definingtheorder pages 8-9, pausch2015cotranslationalcapturingof pages 9-10)

A key mechanistic framework from classic yeast genetics and biochemistry is:
- Nmd3 can associate with 60S subunits even when Rpl10 is substoichiometric, consistent with a maturation order where Rpl10 loads after Nmd3. (west2005definingtheorder pages 7-8)
- Sqt1 binds Rpl10 and can be trapped on 60S particles when the cytoplasmic GTPase Lsg1 is defective, supporting that Sqt1 participates in cytoplasmic loading of Rpl10 and that Lsg1’s GTPase activity is needed to release Sqt1 during/after loading. (west2005definingtheorder pages 8-9)

2.2 Co-translational capture: Sqt1 binds nascent Rpl10 during translation

A major advance was the demonstration that Sqt1 can be recruited to its r-protein client co-translationally (i.e., while Rpl10 is still being synthesized on ribosomes). (pausch2015cotranslationalcapturingof pages 11-12, pausch2015cotranslationalcapturingof pages 8-9)

Mechanistically, affinity purification of Sqt1 enriched RPL10 mRNA relative to other r-protein mRNAs, consistent with Sqt1 engaging translating ribosomes producing its client. (pausch2015cotranslationalcapturingof pages 8-9)

2.3 Structural basis: WD40 β-propeller binding to the extreme N-terminus of Rpl10

Sqt1’s chaperone function is explained by a high-affinity, structure-defined interaction between:
- the top, negatively charged surface of the 8-bladed WD-repeat β-propeller of Sqt1 and
- the extreme N-terminus of Rpl10, particularly residues 2–13, enriched in basic residues.
(pausch2015cotranslationalcapturingof pages 4-5, pausch2015cotranslationalcapturingof pages 8-9)

Specific ionic interactions are critical. For example, Rpl10 arginines (e.g., Arg3/Arg4/Arg7/Arg10) and conserved acidic Sqt1 residues (e.g., Glu110/Glu156/Glu315/Asp420) form key contacts; the Arg10–Glu315 interaction is highlighted as a principal determinant of binding. (pausch2015cotranslationalcapturingof pages 4-5)

3) Localization and cellular context

3.1 Steady-state localization

A synthesis review of dedicated r-protein chaperones reports Sqt1 steady-state localization as cytoplasmic, consistent with its co-translational engagement of nascent Rpl10 and its participation in late cytoplasmic maturation events. (pillet2017holdonto pages 2-3)

3.2 Site of action in biogenesis

The combined evidence supports Sqt1 acting primarily in the cytoplasm, where late 60S maturation steps occur, including Rpl10 loading and Nmd3 release coordinated with Lsg1. (pausch2015cotranslationalcapturingof pages 11-12, west2005definingtheorder pages 8-9)

4) Recent developments (prioritizing 2023–2024): Sqt1 in ribosome repair after oxidative damage

4.1 Concept: chaperone-directed ribosome repair (release-and-replace)

A key 2023 discovery is that certain dedicated r-protein chaperones do more than assist assembly—they can repair mature ribosomes by extracting damaged r-proteins from assembled ribosomes and enabling replacement with newly synthesized protein. (yang2023chaperonedirectedribosomerepair pages 1-3, yang2023chaperonedirectedribosomerepair pages 7-9)

For Sqt1 specifically, Yang et al. (2023) show that oxidized Rpl10 (Rpl10ox) can be released from mature ribosomes in an Sqt1-dependent manner, and that Sqt1 is recruited to ribosomes in vivo upon oxidative stress. (yang2023chaperonedirectedribosomerepair pages 7-9)

4.2 Quantitative/kinetic evidence for Sqt1-dependent turnover of oxidized Rpl10

Using a binding-defective Sqt1 mutant (Sqt1_E315A), Yang et al. provide kinetics supporting that Sqt1 activity is required for efficient Rpl10ox clearance:
- In wild-type yeast, more than half of Rpl10ox is degraded after 30 minutes.
- In the Sqt1_E315A background, Rpl10ox remains stable for >90 minutes.
(yang2023chaperonedirectedribosomerepair pages 7-9)

Functionally, the Sqt1_E315A mutant sensitizes yeast to oxidative stress in quantitative growth assays, linking Sqt1-dependent repair to oxidative stress resistance. (yang2023chaperonedirectedribosomerepair pages 7-9)

4.3 2024 expert synthesis (Annual Review)

A 2024 Annual Review frames these findings as a general, resource-sparing mechanism that conserves ribosome numbers and cellular resources by repairing damaged ribosomes within idle 80S ribosomes rather than degrading entire ribosomes and rebuilding them. In this model, Sqt1 releases damaged uL16/Rpl10, allowing turnover and replacement. (yang2024ribosomeassemblyand pages 9-11)

5) Binding partners and pathway placement

5.1 Direct client/binding partner: Rpl10/uL16

The central binding partner is Rpl10/uL16, bound through its N-terminus (aa 2–13). (pillet2017holdonto pages 2-3, pausch2015cotranslationalcapturingof pages 8-9)

Binding affinity is high: isothermal titration calorimetry reports Kd ≈ 21 nM and 43 nM for S. cerevisiae Sqt1 binding to Rpl10 N-terminal peptides depending on the presence/absence of Met1. (pausch2015cotranslationalcapturingof pages 4-5)

5.2 Functional coupling: Lsg1 and Nmd3 in late cytoplasmic 60S maturation

Genetic/biochemical evidence places Sqt1 in a late cytoplasmic maturation step with:
- Nmd3, an export adaptor that can bind 60S even when Rpl10 is not stoichiometric, and
- Lsg1, a cytoplasmic GTPase whose dominant-negative mutation traps Sqt1 on 60S particles and supports that Lsg1 GTPase activity is required for Sqt1 release during Rpl10 loading.
(west2005definingtheorder pages 7-8, west2005definingtheorder pages 8-9)

6) Statistics and data highlights from recent and key studies

Binding affinity: Sqt1–Rpl10 N-terminus binding Kd ~21–43 nM (ITC). (pausch2015cotranslationalcapturingof pages 4-5)
Co-translational association proxy: Sqt1 purifications show ~25-fold enrichment of RPL10 mRNA (relative enrichment described alongside other chaperone/client pairs). (pausch2015cotranslationalcapturingof pages 8-9)
Oxidative repair kinetics: >50% Rpl10ox degraded by 30 min in WT; stable >90 min with Sqt1_E315A. (yang2023chaperonedirectedribosomerepair pages 7-9)

7) Current applications and real-world implementations

7.1 Experimental leverage: a defined, high-affinity WD40–peptide interaction

Because Sqt1 recognizes a short, basic N-terminal segment of Rpl10 with nanomolar affinity, the Sqt1–Rpl10 system is widely used as a mechanistic model for how cells prevent aggregation of r-proteins and ensure correct handover into pre-ribosomes, including co-translational capture and late maturation checkpoints. (pausch2015cotranslationalcapturingof pages 4-5, pausch2015cotranslationalcapturingof pages 8-9)

7.2 Ribosome homeostasis under stress (oxidative stress resistance)

The 2023–2024 repair work positions Sqt1 as part of a concrete ribosome-homeostasis pathway that protects growth under oxidative stress by enabling targeted repair of ribosomes rather than global degradation/re-synthesis. This is relevant for understanding how eukaryotic cells maintain translation capacity during stress and may inform strategies to modulate stress tolerance in yeast-based systems. (yang2023chaperonedirectedribosomerepair pages 7-9, yang2024ribosomeassemblyand pages 9-11)

7.3 Broader relevance and conservation (expert perspective)

The Annual Review notes that oxidation targets and repair capacity may vary across species and speculates that chaperone-mediated repair may exist in other eukaryotic systems, depending on which r-proteins are oxidation-sensitive and whether corresponding personalized chaperones exist. (yang2024ribosomeassemblyand pages 9-11)

A ribosome-biogenesis-in-health/disease synthesis notes a proposed human ortholog relationship (yeast Sqt1 ↔ human AAMP), while emphasizing that functional conservation needs formal demonstration. (eastham2022regulationofribosome pages 154-156)

8) Visual evidence from key paper

Structural and functional evidence for the Sqt1–Rpl10 interaction and co-translational capture appears in the key figures of Pausch et al. 2015, including the interface mapping and the mRNA enrichment data supporting co-translational capture. (pausch2015cotranslationalcapturingof media a4d1fd57, pausch2015cotranslationalcapturingof media 6c1ecc99, pausch2015cotranslationalcapturingof media 5c28eee9)

9) Summary: functional annotation statement (for databases)

Sqt1 (YIR012W; UniProt P35184) is an essential cytoplasmic WD40-repeat β-propeller protein that functions as a dedicated chaperone/escortin for ribosomal protein Rpl10/uL16. It binds the Rpl10 N-terminus (aa 2–13) with nanomolar affinity, captures Rpl10 co-translationally, maintains its solubility, and promotes its late cytoplasmic loading into pre-60S subunits in coordination with Lsg1 and Nmd3. Recent work (2023–2024) shows Sqt1 also mediates ribosome repair by extracting oxidatively damaged Rpl10 from idle ribosomes and enabling replacement, thereby contributing to oxidative stress resistance and ribosome homeostasis. (pillet2017holdonto pages 2-3, pausch2015cotranslationalcapturingof pages 4-5, west2005definingtheorder pages 8-9, yang2023chaperonedirectedribosomerepair pages 7-9, yang2024ribosomeassemblyand pages 9-11)

Evidence map (condensed)

Aspect	Evidence summary	Key citations	Publication date & URL
Identity / domains	The literature matches the requested target: Sqt1/YIR012W from Saccharomyces cerevisiae is an essential WD-repeat ribosome assembly protein that forms an eight-bladed WD-repeat β-propeller, consistent with UniProt P35184 and InterPro/Pfam WD40 annotations.	(pausch2015cotranslationalcapturingof pages 9-10, pillet2017holdonto pages 2-3, pausch2015cotranslationalcapturingof pages 4-5)	2015-06, https://doi.org/10.1038/ncomms8494; 2017-01, https://doi.org/10.1002/bies.201600153
Primary function	Sqt1 is best understood as a dedicated chaperone/escortin for ribosomal protein Rpl10 (uL16) rather than an enzyme; its core role is to protect newly made Rpl10, maintain its solubility, and promote its productive incorporation into late pre-60S particles.	(pausch2015cotranslationalcapturingof pages 9-10, espinarmarchena2017placeholderfactorsin pages 12-13, pillet2017holdonto pages 2-3)	2015-06, https://doi.org/10.1038/ncomms8494; 2017-05, https://doi.org/10.15698/mic2017.05.572; 2017-01, https://doi.org/10.1002/bies.201600153
Client protein	The specific client is Rpl10/uL16. Multiple studies show direct Sqt1-Rpl10 interaction, and overexpression of RPL10 can suppress sqt1 mutant growth defects, supporting the view that Rpl10 binding is Sqt1’s essential cellular role.	(pausch2015cotranslationalcapturingof pages 9-10, pausch2015cotranslationalcapturingof pages 4-5, west2005definingtheorder pages 8-9)	2015-06, https://doi.org/10.1038/ncomms8494; 2005-05, https://doi.org/10.1128/mcb.25.9.3802-3813.2005
Mechanism in ribosome biogenesis	Sqt1 co-translationally captures nascent Rpl10 by binding its emerging N-terminus, then helps deliver Rpl10 to late cytoplasmic pre-60S particles. Genetic and biochemical evidence place Sqt1 in the pathway where Lsg1-dependent remodeling promotes Rpl10 loading and Nmd3 release during final 60S maturation.	(pausch2015cotranslationalcapturingof pages 11-12, west2005definingtheorder pages 8-9, pausch2015cotranslationalcapturingof pages 8-9, west2005definingtheorder pages 7-8)	2015-06, https://doi.org/10.1038/ncomms8494; 2005-05, https://doi.org/10.1128/mcb.25.9.3802-3813.2005
Mechanism in ribosome repair	Recent work extends Sqt1’s role beyond assembly: under oxidative stress, Sqt1 is recruited to ribosomes and extracts oxidized Rpl10 from idle 80S/60S particles, enabling degradation of damaged Rpl10 and replacement with newly synthesized protein. This defines a chaperone-directed ribosome repair pathway.	(yang2023chaperonedirectedribosomerepair pages 7-9, yang2023chaperonedirectedribosomerepair pages 1-3, yang2024ribosomeassemblyand pages 9-11, yang2023chaperonedirectedribosomerepair pages 18-21)	2023-05, https://doi.org/10.1016/j.molcel.2023.03.030; 2024-10, https://doi.org/10.1146/annurev-cellbio-111822-113326
Localization	Reviews list Sqt1 as primarily cytoplasmic at steady state, fitting its role in co-translational capture of cytosolic nascent Rpl10 and in cytoplasmic late 60S maturation. Repair studies further show recruitment to ribosomes/idle 80S particles during oxidative stress.	(pillet2017holdonto pages 2-3, pausch2015cotranslationalcapturingof pages 11-12, yang2023chaperonedirectedribosomerepair pages 7-9)	2017-01, https://doi.org/10.1002/bies.201600153; 2015-06, https://doi.org/10.1038/ncomms8494; 2023-05, https://doi.org/10.1016/j.molcel.2023.03.030
Key binding interface	Sqt1 binds the extreme N-terminus of Rpl10, especially residues 2–13. The interaction occurs on the negatively charged top surface of the Sqt1 β-propeller and depends strongly on ionic contacts involving Rpl10 basic residues (Arg3/Arg4/Arg7/Arg10) and Sqt1 acidic residues such as Glu110, Glu156, Glu315, Asp420; the Arg10-Glu315 contact is highlighted as a principal determinant.	(pausch2015cotranslationalcapturingof pages 9-10, pausch2015cotranslationalcapturingof pages 4-5, pausch2015cotranslationalcapturingof pages 8-9)	2015-06, https://doi.org/10.1038/ncomms8494
Key quantitative data	Reported quantitative values include Kd ~21 nM and ~43 nM for S. cerevisiae Sqt1 binding to Rpl10 N-terminal peptides, indicating high-affinity recognition. In co-translational capture assays, RPL10 mRNA was enriched ~25-fold in Sqt1 purifications. In oxidative repair, >50% of oxidized Rpl10 was degraded within 30 min in wild type, whereas it remained stable >90 min with the binding-defective Sqt1_E315A mutant.	(pausch2015cotranslationalcapturingof pages 4-5, pausch2015cotranslationalcapturingof pages 8-9, yang2023chaperonedirectedribosomerepair pages 7-9)	2015-06, https://doi.org/10.1038/ncomms8494; 2023-05, https://doi.org/10.1016/j.molcel.2023.03.030
Functional consequences of perturbation	SQT1 is essential/lethal when deleted in yeast. Binding-defective or temperature-sensitive sqt1 alleles impair growth, reduce Rpl10 solubility/delivery, sensitize cells to oxidative stress, and can be partially or strongly rescued by RPL10 overexpression, reinforcing that Sqt1’s central function is Rpl10 handling during assembly and repair.	(pillet2017holdonto pages 2-3, pausch2015cotranslationalcapturingof pages 4-5, yang2023chaperonedirectedribosomerepair pages 7-9)	2017-01, https://doi.org/10.1002/bies.201600153; 2015-06, https://doi.org/10.1038/ncomms8494; 2023-05, https://doi.org/10.1016/j.molcel.2023.03.030

Table: This table summarizes the main functional annotation points for yeast Sqt1/YIR012W, including its validated identity, molecular role, mechanism in ribosome biogenesis and repair, localization, interaction interface, and quantitative evidence. It is useful as a concise evidence map for interpreting UniProt P35184 in current literature.

References

(pausch2015cotranslationalcapturingof pages 9-10): Patrick Pausch, Ujjwala Singh, Yasar Luqman Ahmed, Benjamin Pillet, Guillaume Murat, Florian Altegoer, Gunter Stier, Matthias Thoms, Ed Hurt, Irmgard Sinning, Gert Bange, and Dieter Kressler. Co-translational capturing of nascent ribosomal proteins by their dedicated chaperones. Nature Communications, Jun 2015. URL: https://doi.org/10.1038/ncomms8494, doi:10.1038/ncomms8494. This article has 93 citations and is from a highest quality peer-reviewed journal.
(pillet2017holdonto pages 2-3): Benjamin Pillet, Valentin Mitterer, Dieter Kressler, and Brigitte Pertschy. Hold on to your friends: dedicated chaperones of ribosomal proteins. BioEssays, 39:1-12, Jan 2017. URL: https://doi.org/10.1002/bies.201600153, doi:10.1002/bies.201600153. This article has 93 citations and is from a peer-reviewed journal.
(pausch2015cotranslationalcapturingof pages 4-5): Patrick Pausch, Ujjwala Singh, Yasar Luqman Ahmed, Benjamin Pillet, Guillaume Murat, Florian Altegoer, Gunter Stier, Matthias Thoms, Ed Hurt, Irmgard Sinning, Gert Bange, and Dieter Kressler. Co-translational capturing of nascent ribosomal proteins by their dedicated chaperones. Nature Communications, Jun 2015. URL: https://doi.org/10.1038/ncomms8494, doi:10.1038/ncomms8494. This article has 93 citations and is from a highest quality peer-reviewed journal.
(pillet2017holdonto pages 1-2): Benjamin Pillet, Valentin Mitterer, Dieter Kressler, and Brigitte Pertschy. Hold on to your friends: dedicated chaperones of ribosomal proteins. BioEssays, 39:1-12, Jan 2017. URL: https://doi.org/10.1002/bies.201600153, doi:10.1002/bies.201600153. This article has 93 citations and is from a peer-reviewed journal.
(espinarmarchena2017placeholderfactorsin pages 12-13): Francisco J. Espinar-Marchena, Reyes Babiano, and Jesús de la Cruz. Placeholder factors in ribosome biogenesis: please, pave my way. Microbial Cell, 4:144-168, May 2017. URL: https://doi.org/10.15698/mic2017.05.572, doi:10.15698/mic2017.05.572. This article has 35 citations.
(west2005definingtheorder pages 8-9): Matthew West, John B. Hedges, Anthony Chen, and Arlen W. Johnson. Defining the order in which nmd3p and rpl10p load onto nascent 60s ribosomal subunits. Molecular and Cellular Biology, 25:3802-3813, May 2005. URL: https://doi.org/10.1128/mcb.25.9.3802-3813.2005, doi:10.1128/mcb.25.9.3802-3813.2005. This article has 160 citations and is from a domain leading peer-reviewed journal.
(west2005definingtheorder pages 7-8): Matthew West, John B. Hedges, Anthony Chen, and Arlen W. Johnson. Defining the order in which nmd3p and rpl10p load onto nascent 60s ribosomal subunits. Molecular and Cellular Biology, 25:3802-3813, May 2005. URL: https://doi.org/10.1128/mcb.25.9.3802-3813.2005, doi:10.1128/mcb.25.9.3802-3813.2005. This article has 160 citations and is from a domain leading peer-reviewed journal.
(pausch2015cotranslationalcapturingof pages 11-12): Patrick Pausch, Ujjwala Singh, Yasar Luqman Ahmed, Benjamin Pillet, Guillaume Murat, Florian Altegoer, Gunter Stier, Matthias Thoms, Ed Hurt, Irmgard Sinning, Gert Bange, and Dieter Kressler. Co-translational capturing of nascent ribosomal proteins by their dedicated chaperones. Nature Communications, Jun 2015. URL: https://doi.org/10.1038/ncomms8494, doi:10.1038/ncomms8494. This article has 93 citations and is from a highest quality peer-reviewed journal.
(pausch2015cotranslationalcapturingof pages 8-9): Patrick Pausch, Ujjwala Singh, Yasar Luqman Ahmed, Benjamin Pillet, Guillaume Murat, Florian Altegoer, Gunter Stier, Matthias Thoms, Ed Hurt, Irmgard Sinning, Gert Bange, and Dieter Kressler. Co-translational capturing of nascent ribosomal proteins by their dedicated chaperones. Nature Communications, Jun 2015. URL: https://doi.org/10.1038/ncomms8494, doi:10.1038/ncomms8494. This article has 93 citations and is from a highest quality peer-reviewed journal.
(yang2023chaperonedirectedribosomerepair pages 1-3): Yoon-Mo Yang, Youngeun Jung, Daniel Abegg, Alexander Adibekian, Kate S. Carroll, and Katrin Karbstein. Chaperone-directed ribosome repair after oxidative damage. Molecular Cell, 83:1527-1537.e5, May 2023. URL: https://doi.org/10.1016/j.molcel.2023.03.030, doi:10.1016/j.molcel.2023.03.030. This article has 70 citations and is from a highest quality peer-reviewed journal.
(yang2023chaperonedirectedribosomerepair pages 7-9): Yoon-Mo Yang, Youngeun Jung, Daniel Abegg, Alexander Adibekian, Kate S. Carroll, and Katrin Karbstein. Chaperone-directed ribosome repair after oxidative damage. Molecular Cell, 83:1527-1537.e5, May 2023. URL: https://doi.org/10.1016/j.molcel.2023.03.030, doi:10.1016/j.molcel.2023.03.030. This article has 70 citations and is from a highest quality peer-reviewed journal.
(yang2024ribosomeassemblyand pages 9-11): Yoon-Mo Yang and Katrin Karbstein. Ribosome assembly and repair. Annual Review of Cell and Developmental Biology, 40:241-264, Oct 2024. URL: https://doi.org/10.1146/annurev-cellbio-111822-113326, doi:10.1146/annurev-cellbio-111822-113326. This article has 18 citations and is from a domain leading peer-reviewed journal.
(eastham2022regulationofribosome pages 154-156): MJ Eastham. Regulation of ribosome biogenesis in health and disease. Unknown journal, 2022.
(pausch2015cotranslationalcapturingof media a4d1fd57): Patrick Pausch, Ujjwala Singh, Yasar Luqman Ahmed, Benjamin Pillet, Guillaume Murat, Florian Altegoer, Gunter Stier, Matthias Thoms, Ed Hurt, Irmgard Sinning, Gert Bange, and Dieter Kressler. Co-translational capturing of nascent ribosomal proteins by their dedicated chaperones. Nature Communications, Jun 2015. URL: https://doi.org/10.1038/ncomms8494, doi:10.1038/ncomms8494. This article has 93 citations and is from a highest quality peer-reviewed journal.
(pausch2015cotranslationalcapturingof media 6c1ecc99): Patrick Pausch, Ujjwala Singh, Yasar Luqman Ahmed, Benjamin Pillet, Guillaume Murat, Florian Altegoer, Gunter Stier, Matthias Thoms, Ed Hurt, Irmgard Sinning, Gert Bange, and Dieter Kressler. Co-translational capturing of nascent ribosomal proteins by their dedicated chaperones. Nature Communications, Jun 2015. URL: https://doi.org/10.1038/ncomms8494, doi:10.1038/ncomms8494. This article has 93 citations and is from a highest quality peer-reviewed journal.
(pausch2015cotranslationalcapturingof media 5c28eee9): Patrick Pausch, Ujjwala Singh, Yasar Luqman Ahmed, Benjamin Pillet, Guillaume Murat, Florian Altegoer, Gunter Stier, Matthias Thoms, Ed Hurt, Irmgard Sinning, Gert Bange, and Dieter Kressler. Co-translational capturing of nascent ribosomal proteins by their dedicated chaperones. Nature Communications, Jun 2015. URL: https://doi.org/10.1038/ncomms8494, doi:10.1038/ncomms8494. This article has 93 citations and is from a highest quality peer-reviewed journal.
(yang2023chaperonedirectedribosomerepair pages 18-21): Yoon-Mo Yang, Youngeun Jung, Daniel Abegg, Alexander Adibekian, Kate S. Carroll, and Katrin Karbstein. Chaperone-directed ribosome repair after oxidative damage. Molecular Cell, 83:1527-1537.e5, May 2023. URL: https://doi.org/10.1016/j.molcel.2023.03.030, doi:10.1016/j.molcel.2023.03.030. This article has 70 citations and is from a highest quality peer-reviewed journal.

Citations

pillet2017holdonto pages 2-3
west2005definingtheorder pages 7-8
west2005definingtheorder pages 8-9
pausch2015cotranslationalcapturingof pages 8-9
pausch2015cotranslationalcapturingof pages 4-5
yang2023chaperonedirectedribosomerepair pages 7-9
yang2024ribosomeassemblyand pages 9-11
eastham2022regulationofribosome pages 154-156
pausch2015cotranslationalcapturingof pages 9-10
pillet2017holdonto pages 1-2
espinarmarchena2017placeholderfactorsin pages 12-13
pausch2015cotranslationalcapturingof pages 11-12
yang2023chaperonedirectedribosomerepair pages 1-3
yang2023chaperonedirectedribosomerepair pages 18-21
https://doi.org/10.1038/ncomms8494;
https://doi.org/10.1002/bies.201600153
https://doi.org/10.15698/mic2017.05.572;
https://doi.org/10.1128/mcb.25.9.3802-3813.2005
https://doi.org/10.1016/j.molcel.2023.03.030;
https://doi.org/10.1146/annurev-cellbio-111822-113326
https://doi.org/10.1002/bies.201600153;
https://doi.org/10.1016/j.molcel.2023.03.030
https://doi.org/10.1038/ncomms8494
https://doi.org/10.1038/ncomms8494,
https://doi.org/10.1002/bies.201600153,
https://doi.org/10.15698/mic2017.05.572,
https://doi.org/10.1128/mcb.25.9.3802-3813.2005,
https://doi.org/10.1016/j.molcel.2023.03.030,
https://doi.org/10.1146/annurev-cellbio-111822-113326,

📄 View Raw YAML

id: P35184
gene_symbol: SQT1
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:559292
  label: Saccharomyces cerevisiae
description: >-
  SQT1 encodes an essential cytosolic WD40 beta-propeller protein that functions
  as the dedicated carrier chaperone for ribosomal protein Rpl10/uL16. Sqt1 binds
  the highly basic N-terminus of nascent Rpl10, shields the rRNA-binding surface,
  prevents nonspecific interactions or aggregation, and supports late cytoplasmic
  loading of Rpl10 into pre-60S ribosomal subunits. The older QSR1 suppression
  phenotype and half-mer polysome defects are therefore best interpreted through
  this late 60S assembly/Rpl10 handling function. Recent work also links Sqt1 to
  chaperone-directed repair of oxidatively damaged ribosomes, but the core GO
  annotations remain Rpl10 carrier chaperone activity, cytosolic localization,
  and large ribosomal subunit assembly/biogenesis.
existing_annotations:
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:16429126
  review:
    summary: >-
      Protein binding is true but too generic for Sqt1. The biologically
      informative interaction is client-specific binding to Rpl10 as a dedicated
      ribosomal-protein carrier chaperone.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      GO:0005515 does not capture the direction, specificity, or functional
      consequence of Sqt1-Rpl10 binding. The core molecular function is better
      represented by GO:0140597 protein carrier chaperone, supported directly by
      PMID:26112308.
    supported_by:
    - reference_id: PMID:26112308
      supporting_text: >-
        Affinity purification of four chaperones (Rrb1, Syo1, Sqt1 and Yar1)
        selectively enriched the mRNAs encoding their specific ribosomal protein
        clients (Rpl3, Rpl5, Rpl10 and Rps3).
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:16554755
  review:
    summary: >-
      High-throughput complex data support physical association, but GO:0005515
      is a vague annotation that does not express Sqt1's specific Rpl10 carrier
      chaperone function.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      Retaining generic protein binding would obscure the curated function:
      Sqt1 binds Rpl10 as a dedicated ribosomal-protein chaperone during 60S
      subunit maturation.
    supported_by:
    - reference_id: PMID:26112308
      supporting_text: >-
        X-ray crystallography reveals how the N-terminal, rRNA-binding residues
        of Rpl10 are shielded by Sqt1's WD-repeat beta-propeller, providing
        mechanistic insight into the incorporation of Rpl10 into pre-60S
        subunits.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:27107014
  review:
    summary: >-
      Inter-species high-throughput protein binding observations are not a good
      basis for a yeast SQT1 core function annotation.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      The reported cross-species interactors do not define Sqt1's yeast cellular
      role. SQT1 should be curated around experimentally supported Rpl10 carrier
      chaperone activity and 60S subunit assembly rather than generic protein
      binding.
    supported_by:
    - reference_id: file:yeast/SQT1/SQT1-deep-research-falcon.md
      supporting_text: >-
        Sqt1 is not an enzyme catalyzing a chemical transformation; instead, it
        is best described as a protein-folding/handling factor that binds Rpl10
        and supports its productive assembly into late pre-60S particles.
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:37968396
  review:
    summary: >-
      A large-scale interactome protein binding annotation is less informative
      than the mechanistic Sqt1-Rpl10 chaperone model.
    action: MARK_AS_OVER_ANNOTATED
    reason: >-
      Generic protein binding should not be accepted as a core molecular
      function when a specific carrier chaperone activity for Rpl10 is supported
      by biochemical and structural evidence.
    supported_by:
    - reference_id: PMID:26112308
      supporting_text: >-
        Co-translational capturing of nascent ribosomal proteins by dedicated
        chaperones constitutes an elegant mechanism to prevent unspecific
        interactions and aggregation of ribosomal proteins on their road to
        incorporation.
- term:
    id: GO:0051082
    label: unfolded protein binding
  evidence_type: IDA
  original_reference_id: PMID:26112308
  review:
    summary: >-
      The evidence from PMID:26112308 supports a dedicated Rpl10 carrier
      chaperone activity, not generic binding to unfolded proteins.
    action: MODIFY
    reason: >-
      Sqt1 binds the Rpl10 N-terminus with client specificity and shields
      aggregation-prone rRNA-binding residues before Rpl10 incorporation into
      pre-60S subunits. GO:0140597 protein carrier chaperone is the appropriate
      replacement.
    proposed_replacement_terms:
    - id: GO:0140597
      label: protein carrier chaperone
    supported_by:
    - reference_id: PMID:26112308
      supporting_text: >-
        X-ray crystallography reveals how the N-terminal, rRNA-binding residues
        of Rpl10 are shielded by Sqt1's WD-repeat beta-propeller, providing
        mechanistic insight into the incorporation of Rpl10 into pre-60S
        subunits.
- term:
    id: GO:0005737
    label: cytoplasm
  evidence_type: HDA
  original_reference_id: PMID:11914276
  review:
    summary: >-
      Cytoplasmic localization is consistent with Sqt1's role in co-translational
      Rpl10 capture and late cytoplasmic 60S maturation.
    action: ACCEPT
    reason: >-
      The high-throughput cytoplasm annotation agrees with the mechanistic model
      and with the more specific cytosol annotation.
    supported_by:
    - reference_id: file:yeast/SQT1/SQT1-deep-research-falcon.md
      supporting_text: >-
        The combined evidence supports Sqt1 acting primarily in the cytoplasm,
        where late 60S maturation steps occur, including Rpl10 loading and Nmd3
        release coordinated with Lsg1.
- term:
    id: GO:0042273
    label: ribosomal large subunit biogenesis
  evidence_type: IMP
  original_reference_id: PMID:26112308
  review:
    summary: >-
      Sqt1 is a dedicated Rpl10 chaperone required for proper late 60S ribosomal
      subunit maturation.
    action: ACCEPT
    reason: >-
      This process annotation accurately captures Sqt1's role in ribosomal large
      subunit biogenesis through client-specific Rpl10 handling.
    supported_by:
    - reference_id: PMID:26112308
      supporting_text: >-
        X-ray crystallography reveals how the N-terminal, rRNA-binding residues
        of Rpl10 are shielded by Sqt1's WD-repeat β-propeller, providing
        mechanistic insight into the incorporation of Rpl10 into pre-60S
        subunits.
- term:
    id: GO:0000027
    label: ribosomal large subunit assembly
  evidence_type: IMP
  original_reference_id: PMID:9271392
  review:
    summary: >-
      The original SQT1 study showed half-mer polysome defects and reduced Qsr1
      levels on free 60S subunits when SQT1 function was reduced, supporting a
      late 60S assembly function.
    action: ACCEPT
    reason: >-
      This annotation remains correct and is strengthened by later evidence that
      Sqt1 chaperones Rpl10 for late pre-60S incorporation.
    supported_by:
    - reference_id: PMID:9271392
      supporting_text: >-
        Loss of SQT1 function by down regulation from an inducible promoter
        results in formation of half-mer polyribosomes and decreased Qsr1p
        levels on free 60S subunits. Sqt1p thus appears to be involved in a late
        step of 60S subunit assembly or modification in the cytoplasm.
- term:
    id: GO:0005829
    label: cytosol
  evidence_type: IDA
  original_reference_id: PMID:9271392
  review:
    summary: >-
      Cytosolic localization is consistent with the original biochemical
      fractionation and with Sqt1's role in co-translational Rpl10 capture and
      late cytoplasmic 60S maturation.
    action: ACCEPT
    reason: >-
      Cytosol is the best-supported core cellular location for Sqt1 function.
    supported_by:
    - reference_id: PMID:9271392
      supporting_text: >-
        Sqt1p thus appears to be involved in a late step of 60S subunit assembly
        or modification in the cytoplasm.
references:
- id: PMID:11914276
  title: Subcellular localization of the yeast proteome
  findings: []
- id: PMID:16429126
  title: Proteome survey reveals modularity of the yeast cell machinery
  findings: []
- id: PMID:16554755
  title: Global landscape of protein complexes in the yeast Saccharomyces cerevisiae
  findings: []
- id: PMID:26112308
  title: Co-translational capturing of nascent ribosomal proteins by their dedicated chaperones
  findings:
  - statement: >-
      Sqt1 is a dedicated chaperone for Rpl10 and shields Rpl10's N-terminal
      rRNA-binding residues during incorporation into pre-60S subunits.
    supporting_text: >-
      Affinity purification of four chaperones (Rrb1, Syo1, Sqt1 and Yar1)
      selectively enriched the mRNAs encoding their specific ribosomal protein
      clients (Rpl3, Rpl5, Rpl10 and Rps3). X-ray crystallography reveals how
      the N-terminal, rRNA-binding residues of Rpl10 are shielded by Sqt1's
      WD-repeat beta-propeller.
- id: PMID:27107014
  title: An inter-species protein-protein interaction network across vast evolutionary distance
  findings: []
- id: PMID:37968396
  title: The social and structural architecture of the yeast protein interactome
  findings: []
- id: PMID:9271392
  title: >-
    SQT1, which encodes an essential WD domain protein of Saccharomyces
    cerevisiae, suppresses dominant-negative mutations of the ribosomal protein
    gene QSR1
  findings:
  - statement: >-
      Sqt1 is required for late 60S subunit assembly or modification in the
      cytoplasm.
    supporting_text: >-
      Loss of SQT1 function by down regulation from an inducible promoter
      results in formation of half-mer polyribosomes and decreased Qsr1p levels
      on free 60S subunits.
- id: file:yeast/SQT1/SQT1-deep-research-falcon.md
  title: Falcon deep research report for SQT1
  findings:
  - statement: >-
      Falcon supports SQT1 as a cytosolic Rpl10 carrier chaperone required for
      late 60S maturation and ribosome homeostasis.
    supporting_text: >-
      Sqt1 is an essential cytoplasmic WD40-repeat beta-propeller protein that
      functions as a dedicated chaperone/escortin for ribosomal protein
      Rpl10/uL16.
core_functions:
- description: >-
    Sqt1 is a dedicated cytosolic carrier chaperone for ribosomal protein
    Rpl10/uL16. It co-translationally recognizes the Rpl10 N-terminus, shields
    aggregation-prone rRNA-binding residues, and promotes Rpl10 incorporation
    during late cytoplasmic 60S ribosomal subunit maturation.
  molecular_function:
    id: GO:0140597
    label: protein carrier chaperone
  directly_involved_in:
  - id: GO:0042273
    label: ribosomal large subunit biogenesis
  - id: GO:0000027
    label: ribosomal large subunit assembly
  locations:
  - id: GO:0005829
    label: cytosol
  supported_by:
  - reference_id: PMID:26112308
    supporting_text: >-
      X-ray crystallography reveals how the N-terminal, rRNA-binding residues of
      Rpl10 are shielded by Sqt1's WD-repeat beta-propeller, providing
      mechanistic insight into the incorporation of Rpl10 into pre-60S subunits.
  - reference_id: PMID:9271392
    supporting_text: >-
      Sqt1p thus appears to be involved in a late step of 60S subunit assembly
      or modification in the cytoplasm.
proposed_new_terms: []
suggested_questions:
- question: >-
    Which handoff factors receive Rpl10 from Sqt1 during Lsg1- and Nmd3-linked
    late 60S maturation?
- question: >-
    How much of Sqt1's essential growth role reflects co-translational Rpl10
    capture versus later ribosome repair of damaged Rpl10?
- question: >-
    Are non-Rpl10 high-throughput Sqt1 interactors reproducible functional
    partners, contaminants, or context-specific stress interactions?
suggested_experiments:
- description: >-
    Use separation-of-function SQT1 interface mutants to compare Rpl10 binding,
    Rpl10 solubility, 60S subunit maturation, and oxidative-stress repair in the
    same strain background.
  experiment_type: genetics
- description: >-
    Reconstitute Sqt1-mediated Rpl10 handoff to pre-60S particles with purified
    late maturation factors and measure dependence on Lsg1 and Nmd3 remodeling.
  experiment_type: biochemistry
- description: >-
    Validate high-throughput Sqt1 protein-binding partners by reciprocal
    co-immunoprecipitation and test whether any interactions change under
    ribosome assembly stress or oxidative stress.
  experiment_type: proteomics

SQT1

Gene Description

Existing Annotations Review

Core Functions

Sqt1 is a dedicated cytosolic carrier chaperone for ribosomal protein Rpl10/uL16. It co-translationally recognizes the Rpl10 N-terminus, shields aggregation-prone rRNA-binding residues, and promotes Rpl10 incorporation during late cytoplasmic 60S ribosomal subunit maturation.

References

Suggested Questions for Experts

Suggested Experiments

📚 Additional Documentation

Deep Research Falcon

Question

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

Target Gene/Protein Identity (from UniProt):

MANDATORY VERIFICATION STEPS:

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

Research Target:

Output

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

Target Gene/Protein Identity (from UniProt):

MANDATORY VERIFICATION STEPS:

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

Research Target:

Research Report: Functional Annotation of Saccharomyces cerevisiae SQT1 (UniProt P35184; YIR012W)

0) Target verification (mandatory)

1) Key concepts and definitions (current understanding)

1.1 Dedicated ribosomal-protein (r-protein) chaperones

1.2 What Sqt1 is (and is not)

2) Molecular function of Sqt1: primary role and mechanism

2.1 Primary function: chaperoning and delivery of Rpl10/uL16 for late cytoplasmic 60S maturation

2.2 Co-translational capture: Sqt1 binds nascent Rpl10 during translation

2.3 Structural basis: WD40 β-propeller binding to the extreme N-terminus of Rpl10

3) Localization and cellular context

3.1 Steady-state localization

3.2 Site of action in biogenesis

4) Recent developments (prioritizing 2023–2024): Sqt1 in ribosome repair after oxidative damage

4.1 Concept: chaperone-directed ribosome repair (release-and-replace)

4.2 Quantitative/kinetic evidence for Sqt1-dependent turnover of oxidized Rpl10

4.3 2024 expert synthesis (Annual Review)

5) Binding partners and pathway placement

5.1 Direct client/binding partner: Rpl10/uL16

5.2 Functional coupling: Lsg1 and Nmd3 in late cytoplasmic 60S maturation

6) Statistics and data highlights from recent and key studies

7) Current applications and real-world implementations

7.1 Experimental leverage: a defined, high-affinity WD40–peptide interaction

7.2 Ribosome homeostasis under stress (oxidative stress resistance)

7.3 Broader relevance and conservation (expert perspective)

8) Visual evidence from key paper

9) Summary: functional annotation statement (for databases)

Evidence map (condensed)

Citations

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