preribosome, small subunit precursor

GO:0030688 · Ribonucleoprotein · Ribonucleoprotein complex · Proposed

A preribosomal complex consisting of 20S pre-rRNA, ribosomal proteins including late-associating small subunit proteins, and associated proteins; a precursor of the eukaryotic cytoplasmic small ribosomal subunit. [GO:0030688]

Synonyms: 43S preribosome

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
20S pre-rRNA	Rna	part of	Reviewed label only (reviewed name; no accession asserted)				20S precursor rRNA assembled into a eukaryotic cytoplasmic small-subunit preribosomal precursor. `GO:0030688` GO:0030688 defines the small-subunit precursor preribosome as containing 20S pre-rRNA. `SO:0002393` SO:0002393 denotes the broader precursor_RNA class, not the exact 20S precursor rRNA species.
small-subunit preribosome protein cohort	Protein	part of	Reviewed label only (reviewed name; no accession asserted)				Ribosomal proteins and associated assembly factors carried by eukaryotic small-subunit preribosome precursors. `GO:0030688` GO:0030688 defines the small-subunit precursor preribosome as containing ribosomal proteins, including late-associating small-subunit ribosomal proteins, and associated proteins.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: GO:0030688 notes that this small-subunit precursor preribosome is a 43S complex in Saccharomyces; broader eukaryotic distribution is left for a follow-up curation pass. [GO:0030688]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Budding yeast is the model for the 43S small-subunit preribosome precursor described in the GO:0030688 comment. [GO:0030688]

Functions

ribosomal small subunit biogenesis GO:0042274 — As a precursor of the eukaryotic cytoplasmic small ribosomal subunit, the small-subunit preribosome participates in small-subunit biogenesis.
- GO:0042274 GO:0042274 is the Gene Ontology biological-process term for ribosomal small subunit biogenesis.
- GO:0030688 GO:0030688 defines this preribosome as a precursor of the eukaryotic cytoplasmic small ribosomal subunit.
ribosome biogenesis GO:0042254 — The small-subunit preribosome is a preribosomal complex formed as part of the broader ribosome-biogenesis program.
- GO:0042254 GO:0042254 is the Gene Ontology biological-process term for ribosome biogenesis.
- GO:0030684 GO:0030684 defines preribosomal complexes as being formed during ribosome biogenesis.

Mechanism graphs

20S pre-rRNA and proteins form small-subunit preribosome precursors (ASSEMBLY)

GO defines the small-subunit precursor preribosome as a preribosomal complex containing 20S pre-rRNA, ribosomal proteins including late-associating small-subunit proteins, and associated proteins.

Subject	Predicate	Object	Evidence
20S pre-rRNA	contributes constituents to	preribosome, small subunit precursor	`GO:0030688` GO:0030688 defines the complex as containing 20S pre-rRNA.
small-subunit preribosome protein cohort	contributes constituents to	preribosome, small subunit precursor	`GO:0030688` GO:0030688 defines the complex as containing ribosomal proteins and associated proteins.
preribosome, small subunit precursor	participates in	ribosomal small subunit biogenesis	`GO:0030688` GO:0030688 defines this preribosome as a precursor of the eukaryotic cytoplasmic small ribosomal subunit. `GO:0042274` GO:0042274 is the process term for ribosomal small subunit biogenesis.

Discussions

CURATION_TODO (OPEN): Resolve exact small-subunit preribosome precursor RNA, ribosomal-protein and associated assembly-factor boundaries. GO:0030688 defines a eukaryotic cytoplasmic small-subunit preribosome precursor with 20S pre-rRNA, ribosomal proteins including late-associating small-subunit proteins, and associated proteins. Exact source-neutral boundaries for the 20S precursor rRNA and protein cohorts need narrower literature-backed curation.

Evidence

GO:0030688 Gene Ontology cellular-component term for the preribosome, small subunit precursor and its 43S preribosome narrow synonym.
GO:0030684 Gene Ontology cellular-component parent term for preribosomal complexes.
GO:0042274 Gene Ontology biological-process term for ribosomal small subunit biogenesis.
GO:0042254 Gene Ontology biological-process term for ribosome biogenesis.
SO:0002393 Sequence Ontology term for the broader precursor_RNA class, which is not specific to 20S pre-rRNA.
PMID:10567516 PubMed identifier for Kressler, Linder and de la Cruz 1999, the review publication cited in the GO:0030688 definition.
DOI:10.1128/MCB.19.12.7897 DOI for Kressler, Linder and de la Cruz 1999, 'Protein trans-Acting Factors Involved in Ribosome Biogenesis in Saccharomyces cerevisiae', verified through NCBI E-utilities.

Curation history

2026-09-25T20:04:57Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-25T20:05:32Z codex · EXPANDED_RECORD — Added 43S preribosome synonymy, preribosome parentage, reviewed-label-only 20S pre-rRNA and protein-cohort components, a conservative budding-yeast example, ribosomal small-subunit biogenesis functions, GO/SO/PubMed evidence, a nonmechanistic constituent graph and a TODO for exact component boundaries.

Source: data/structures/ribonucleoprotein/preribosome_small_subunit_precursor.yaml