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. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN001410872 · PTN001410872 SUPPORTS TRANSFER Current PTHR13347 PAINT places protein import into nucleus on the conserved fungal/metazoan Syo1/HEATR3 node, supported by direct S. cerevisiae and human evidence for Rpl5/Rpl11 co-import. 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. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN001410872 · PTN001410872 SUPPORTS TRANSFER Current PTHR13347 PAINT places ribosomal large subunit biogenesis on the conserved fungal/metazoan Syo1/HEATR3 node, matching Syo1's experimentally established 5S RNP import and assembly role. 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 obsolete and is too broad for Syo1. The more informative molecular-function term is protein carrier chaperone, reflecting cargo binding and escort between cytoplasm and nucleus. Propagation Review Root cause: SOURCE STALE OR MISSING Sources checked: PANTHER:PTN001410872 · PTN001410872 SOURCE STALE OR MISSING GO:0051082 was formally obsoleted; the legacy 2017 GOA IBA row persists after the obsolete assertion stopped serializing from the current PTHR13347 PAINT node, which carries only protein import into nucleus and ribosomal large subunit biogenesis. 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: GO:0051082 is obsolete and 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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Download this section (compressed HTML)Transport adaptor or symportin; assembly chaperone that co-translationally associates with nascent Rpl5p, preventing aggregation; facilitates synchronized nuclear coimport of two 5S-rRNA binding proteins, Rpl5p and Rpl11p, mediated by import receptor Kap104p; required for biogenesis of the large ribosomal subunit; green fluorescent protein (GFP)-fusion protein localizes to the cytoplasm and nucleus
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