SYO1 encodes Syo1/symportin 1, a conserved ARM/HEAT-repeat nuclear import adaptor and dedicated ribosomal-protein carrier chaperone. Syo1 binds the 5S-rRNA-associated ribosomal proteins Rpl5/uL18 and Rpl11/uL5, recruits the import receptor Kap104, and coordinates their cytoplasm-to-nucleus co-import. After RanGTP-dependent release from Kap104, the Syo1-Rpl5-Rpl11 cargo complex can be handed to 5S rRNA, linking ribosomal-protein import with early 5S RNP assembly and 60S ribosomal large subunit biogenesis. Recent structural work places Syo1 in a conserved hexameric nascent 5S RNP precursor with 5S rRNA, Rpl5/uL18, Rpl11/uL5, Rpf2 and Rrs1 (PMID:37291423). Syo1 is therefore best curated as a specific protein carrier chaperone/import adaptor, not as a generic unfolded-protein binding factor.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0006606 protein import into nucleus | IBA GO_REF:0000033 | ACCEPT | Summary: The PANTHER/IBA annotation is consistent with direct yeast evidence and UniProt family context. Syo1 is a specialized import adaptor that brings Rpl5 and Rpl11 into the nucleus through Kap104. Reason: Nuclear import of the Rpl5-Rpl11 cargo pair is a core Syo1 biological process and is well supported by the experimental IGI annotation and the Falcon synthesis. Supporting Evidence: PMID:23118189 Syo1 concomitantly binds Rpl5-Rpl11 and furthermore recruits the import receptor Kap104. file:yeast/SYO1/SYO1-deep-research-falcon.md Falcon identifies Syo1 as a shuttling nuclear import adaptor for Rpl5 and Rpl11. |
| GO:0042273 ribosomal large subunit biogenesis | IBA GO_REF:0000033 | ACCEPT | Summary: Syo1-mediated co-import of Rpl5 and Rpl11 is coupled to 5S RNP formation and 60S ribosomal large subunit assembly. The IBA annotation transfers a conserved, experimentally supported ribosome-biogenesis role. Reason: Ribosomal large subunit biogenesis is a core biological process for Syo1 and is supported by mutant ribosome-biogenesis phenotypes and mechanistic studies of 5S RNP assembly. Supporting Evidence: PMID:19806183 we associate the new genes with specific aspects of ribosomal subunit maturation, ribosomal particle association, and ribosomal subunit nuclear export file:yeast/SYO1/SYO1-deep-research-falcon.md Falcon describes Syo1 as an import adaptor and assembly chaperone that supports 5S RNP and 60S biogenesis. |
| GO:0051082 unfolded protein binding | IBA GO_REF:0000033 | MODIFY | Summary: Syo1 does protect ribosomal-protein cargo from inappropriate interactions, but the biology is not generic unfolded-protein binding. It is a dedicated carrier chaperone/import adaptor for Rpl5 and Rpl11. Reason: GO:0051082 is too broad for Syo1. The more informative molecular-function term is protein carrier chaperone, reflecting cargo binding and escort between cytoplasm and nucleus. Proposed replacements: protein carrier chaperone Supporting Evidence: PMID:26112308 Co-translational capturing of nascent ribosomal proteins by dedicated chaperones file:yeast/SYO1/SYO1-deep-research-falcon.md Falcon frames Syo1 as a dedicated transport adaptor/chaperone rather than a general unfolded-protein binding factor. |
| GO:0005634 nucleus | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular-location mapping to nucleus is consistent with Syo1's import-adaptor role and with direct localization evidence. Reason: Syo1 acts in the nucleus after Kap104-mediated import of the Syo1-Rpl5-Rpl11 complex and is directly observed in nuclear localization datasets. Supporting Evidence: PMID:23118189 The Syo1-Rpl5-Rpl11 import complex is released from Kap104 by RanGTP |
| GO:0005737 cytoplasm | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular-location mapping to cytoplasm is consistent with Syo1 capturing newly synthesized ribosomal-protein cargo before nuclear import. Reason: Syo1 functions as a shuttling factor: it binds Rpl5/Rpl11 in the cytoplasm and carries them to the nucleus. Cytoplasm is therefore a relevant localization, although the steady-state signal can be mainly nuclear. Supporting Evidence: PMID:23118189 Syo1 can shuttle back to the cytoplasm |
| GO:0015031 protein transport | IEA GO_REF:0000043 | MODIFY | Summary: The UniProt keyword-derived protein transport annotation captures the general concept, but Syo1's transport function is specifically nuclear import of ribosomal proteins. Reason: Replace the broad GO:0015031 term with GO:0006606 protein import into nucleus, which matches the experimentally demonstrated Syo1-Kap104 mechanism. Proposed replacements: protein import into nucleus Supporting Evidence: PMID:23118189 facilitates synchronized coimport of the two 5S-rRNA binding proteins Rpl5 and Rpl11 |
| GO:0042254 ribosome biogenesis | IEA GO_REF:0000043 | MODIFY | Summary: The broad ribosome biogenesis annotation is correct in direction, but Syo1 is specifically tied to 5S RNP/60S large subunit biogenesis. Reason: GO:0042273 ribosomal large subunit biogenesis is the better replacement because Syo1 escorts Rpl5/Rpl11 for 5S RNP formation during 60S assembly. Proposed replacements: ribosomal large subunit biogenesis Supporting Evidence: PMID:19806183 new genes with specific aspects of ribosomal subunit maturation, ribosomal particle association, and ribosomal subunit nuclear export |
| GO:0051082 unfolded protein binding | IDA PMID:26112308 Co-translational capturing of nascent ribosomal proteins by ... | MODIFY | Summary: The IDA evidence shows dedicated co-translational capture of ribosomal protein clients by Syo1, not general binding to unfolded proteins. Reason: Syo1 is best represented as a protein carrier chaperone: it captures and escorts a defined ribosomal-protein cargo pair rather than acting as a broad unfolded-protein binding chaperone. Proposed replacements: protein carrier chaperone Supporting Evidence: PMID:26112308 Affinity purification of four chaperones (Rrb1, Syo1, Sqt1 and Yar1) selectively enriched the mRNAs encoding their specific ribosomal protein clients file:yeast/SYO1/SYO1-deep-research-falcon.md Falcon supports replacing generic unfolded-protein binding with a dedicated carrier-chaperone interpretation. |
| GO:0005634 nucleus | HDA PMID:14562095 Global analysis of protein localization in budding yeast. | ACCEPT | Summary: High-throughput GFP localization placed Syo1 in the nucleus, matching its biological role in nuclear delivery and 5S RNP assembly. Reason: Nuclear localization is biologically meaningful for Syo1 and is also supported by UniProt and the mechanistic nuclear import literature. Supporting Evidence: PMID:14562095 Global analysis of protein localization in budding yeast. |
| GO:0005737 cytoplasm | HDA PMID:14562095 Global analysis of protein localization in budding yeast. | ACCEPT | Summary: High-throughput GFP localization also detected Syo1 in the cytoplasm, consistent with cargo capture before nuclear import and shuttling back from the nucleus. Reason: Cytoplasmic localization is part of the Syo1 transport cycle and should be retained, even though its steady-state enrichment may be nuclear. Supporting Evidence: PMID:14562095 Global analysis of protein localization in budding yeast. |
| GO:0006606 protein import into nucleus | IGI PMID:23118189 Synchronizing nuclear import of ribosomal proteins with ribo... | ACCEPT | Summary: The genetic interaction annotation directly reflects the Science 2012 work showing that Syo1 mediates Kap104-dependent nuclear co-import of Rpl5 and Rpl11. Reason: This is one of the central experimentally supported Syo1 annotations and captures the import component of its core function. Supporting Evidence: PMID:23118189 facilitates synchronized coimport of the two 5S-rRNA binding proteins Rpl5 and Rpl11 PMID:23118189 The Syo1-Rpl5-Rpl11 import complex is released from Kap104 by RanGTP |
| GO:0042273 ribosomal large subunit biogenesis | IMP PMID:19806183 Rational extension of the ribosome biogenesis pathway using ... | ACCEPT | Summary: Mutant phenotyping and the later mechanistic literature support Syo1's role in 60S large subunit biogenesis through coordinated import and assembly of the 5S RNP protein module. Reason: GO:0042273 is the appropriate specific biological-process term for the ribosome-biogenesis effect of SYO1. Supporting Evidence: PMID:19806183 confirming involvement of at least 15 new genes file:yeast/SYO1/SYO1-deep-research-falcon.md Falcon summarizes reduced free 60S, half-mer polysome, and 5S RNP assembly evidence for Syo1. |
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Download this section (compressed HTML)Q: Should Syo1 receive a direct curated GO:0140597 protein carrier chaperone annotation, replacing the older unfolded protein binding annotations?
Suggested experts: Kressler D, Hurt E, Bange G
Experiment: Combine structure-guided SYO1 interface mutants with Rpl5/Rpl11 co-import assays, 5S RNP co-purification, and polysome profiling to distinguish defects in cargo capture, nuclear import, and downstream 60S assembly.
Hypothesis: Syo1's carrier-chaperone function depends on separable cargo-binding, Kap104-binding, and 5S-rRNA-contact surfaces.
Type: structure-guided ribosome biogenesis assay
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