ubl-1

Gene Description

ubl-1 encodes a bifunctional ubiquitin-like protein 1-ribosomal protein eS31 fusion protein (the Caenorhabditis briggsae ortholog of the RPS27A/UBA80-type fusion). It is synthesized as a single precursor in which an N-terminal ubiquitin-like domain (residues 1-70) is fused to the C-terminal small ribosomal subunit protein eS31 (40S ribosomal protein S27a; residues 71-163). The precursor is co-translationally cleaved by deubiquitinating enzymes to release two products with distinct functions. The N-terminal moiety is a ubiquitin-like protein that, once liberated, contributes to the cellular pool of free ubiquitin used to covalently tag substrate proteins, marking them for modification-dependent fates including proteasomal degradation. The C-terminal moiety is a zinc-finger-containing structural protein of the small (40S) ribosomal subunit that is required for translation; fusion to the ubiquitin-like domain is thought to aid its folding, stability, and incorporation into the ribosome. The mature ribosomal protein localizes to the cytosolic ribosome, and the released ubiquitin moiety acts in protein ubiquitination throughout the cell.

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0005634 nucleus	IBA GO_REF:0000033	KEEP AS NON CORE	Summary: Phylogenetic (IBA) localization to the nucleus, propagated across the ribosomal protein eS31/ubiquitin fusion family. Ribosomal protein assembly begins in the nucleolus/nucleus and free ubiquitin acts throughout the cell including the nucleus, so a nuclear location is biologically plausible but is not a core, defining localization of this gene product. Kept as a non-core localization.
GO:0003735 structural constituent of ribosome	IBA GO_REF:0000033	ACCEPT	Summary: Core molecular function of the C-terminal eS31 (RPS27a) moiety. After cleavage of the ubiquitin-like domain, the mature ribosomal protein is a structural constituent of the small (40S) ribosomal subunit. Strongly supported by family-wide phylogenetic evidence and by the conserved eS31 domain architecture (zinc-finger ribosomal fold). Accepted as a core function.
GO:0022626 cytosolic ribosome	IBA GO_REF:0000033	ACCEPT	Summary: Correct cellular location for the mature eS31 ribosomal protein, which functions as part of the cytosolic 40S ribosomal subunit during translation. Consistent with the structural constituent of ribosome function and the eS31 family. Accepted.
GO:0031386 protein tag activity	IBA GO_REF:0000033	ACCEPT	Summary: Captures the core molecular function of the N-terminal ubiquitin-like moiety. After cleavage, the released ubiquitin-like protein is covalently conjugated to substrate lysines (an isopeptide crosslink is annotated at Gly70) and serves as a tag marking proteins for downstream fates. This is the canonical ubiquitin/ubiquitin-like function and a defining role of the gene's bifunctional product. Accepted as a core function.
GO:0019941 modification-dependent protein catabolic process	IBA GO_REF:0000033	KEEP AS NON CORE	Summary: The free ubiquitin released from the fusion contributes to the cellular ubiquitin pool used to target substrates for proteasomal (modification-dependent) degradation. This is a downstream process role of the ubiquitin moiety rather than the gene product's own defining molecular function, but it is a genuine and well-supported aspect of ubiquitin biology. Retained as a non-core process annotation.
GO:0016567 protein ubiquitination	IBA GO_REF:0000033	KEEP AS NON CORE	Summary: The cleaved ubiquitin-like moiety supplies free ubiquitin for conjugation onto target proteins, so involvement in protein ubiquitination is correct. This is the biological-process counterpart of the protein tag activity function. Retained as a non-core process annotation reflecting the ubiquitin side of this bifunctional product.
GO:0003735 structural constituent of ribosome	IEA GO_REF:0000002	ACCEPT	Summary: InterPro-based electronic annotation (IPR002906, ribosomal eS31) corroborating the IBA structural constituent of ribosome call. Consistent with the C-terminal eS31 domain and the core ribosomal function. Accepted.
GO:0005840 ribosome	IEA GO_REF:0000002	MODIFY	Summary: InterPro-derived (IPR002906) localization to the ribosome. Correct but more general than the cytosolic ribosome (GO:0022626) term already annotated by IBA. The mature eS31 protein is a cytosolic 40S subunit component, so the more specific term better reflects the location. Proposed replacements: cytosolic ribosome
GO:0006412 translation	IEA GO_REF:0000120	KEEP AS NON CORE	Summary: Automated multi-method (ARBA/InterPro) annotation to translation, the biological process in which the eS31 ribosomal protein participates as a 40S subunit constituent. Correct and consistent with the structural constituent of ribosome function, though it is a broad process term rather than the gene's defining molecular function. Retained as a non-core process.

Gene Description

Existing Annotations Review

Core Functions

Structural constituent of the small (40S) cytosolic ribosomal subunit. The mature C-terminal eS31 (RPS27a) moiety, released after cleavage of the ubiquitin-like domain, is a zinc-finger ribosomal protein that assembles into the 40S subunit and is required for translation.

Ubiquitin-like protein tag. The N-terminal ubiquitin-like moiety, after proteolytic release from the fusion, contributes free ubiquitin that is covalently conjugated to substrate proteins (isopeptide-linked via Gly70), tagging them for modification-dependent fates including proteasomal degradation.

References

📄 View Raw YAML