90S preribosome

GO:0030686 · Ribonucleoprotein · Ribonucleoprotein complex · Proposed

A large ribonucleoprotein complex considered to be the earliest preribosomal complex. In S. cerevisiae, it has a size of 90S and consists of the 35S pre-rRNA, early-associating ribosomal proteins most of which are part of the small ribosomal subunit, the U3 snoRNA and associated proteins. [GO:0030686]

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

Components

Component	Type	Part of / acts on	Grounding	Role
35S pre-rRNA	Rna	part of	Reviewed label only (reviewed name; no accession asserted)	Precursor ribosomal RNA constituent of budding-yeast 90S preribosomes. `GO:0030686` GO:0030686 defines the budding-yeast 90S preribosome as containing 35S pre-rRNA. `DOI:10.1016/s1097-2765(02)00579-8` Grandi et al. 2002 characterized early 90S pre-ribosomal particles that coprecipitated 35S pre-rRNA.
U3 snoRNA	Rna	part of	Reviewed label only (reviewed name; no accession asserted)	Small nucleolar RNA constituent associated with the budding-yeast 90S preribosome through the U3 snoRNP. `GO:0030686` GO:0030686 defines the budding-yeast 90S preribosome as containing U3 snoRNA. `DOI:10.1016/s1097-2765(02)00579-8` Grandi et al. 2002 characterized 90S pre-ribosomal particles that coprecipitated U3 snoRNA and included the U3 snoRNP.
90S preribosome protein cohort	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	Early-associating mostly small-subunit ribosomal proteins and associated 40S subunit processing factors in the 90S preribosome. `GO:0030686` GO:0030686 describes early-associating ribosomal proteins, most of which are part of the small ribosomal subunit, and associated proteins in the budding-yeast 90S preribosome. `DOI:10.1016/s1097-2765(02)00579-8` Grandi et al. 2002 identified non-ribosomal proteins, including U3-associated proteins and other 18S-rRNA synthesis factors, in 90S pre-ribosomal particles.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: GO:0030686 defines the 90S preribosome in the budding-yeast assembly context; broader eukaryotic distribution is left for a follow-up curation pass. [GO:0030686]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Budding yeast is the model in which Grandi et al. 2002 characterized early 90S pre-ribosomes containing 35S pre-rRNA, U3 snoRNA and 40S processing factors. [DOI:10.1016/s1097-2765(02)00579-8]

Functions

ribosome biogenesis GO:0042254 — As an early preribosomal ribonucleoprotein, the 90S preribosome contributes to assembly of ribosomal subunits.
- 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.
- DOI:10.1016/s1097-2765(02)00579-8 Grandi et al. 2002 characterized early pre-ribosomal particles and their association with 40S subunit assembly factors.

Mechanism graphs

35S pre-rRNA, U3 snoRNA and proteins form 90S preribosomes (ASSEMBLY)

GO defines the 90S preribosome as an early budding-yeast preribosomal ribonucleoprotein containing 35S pre-rRNA, U3 snoRNA, early-associating mostly small-subunit ribosomal proteins and associated proteins.

Subject	Predicate	Object	Evidence
35S pre-rRNA	contributes constituents to	90S preribosome	`GO:0030686` GO:0030686 defines the 90S preribosome as containing 35S pre-rRNA.
U3 snoRNA	contributes constituents to	90S preribosome	`GO:0030686` GO:0030686 defines the 90S preribosome as containing U3 snoRNA. `DOI:10.1016/s1097-2765(02)00579-8` Grandi et al. 2002 characterized 90S particles that coprecipitated U3 snoRNA.
90S preribosome protein cohort	contributes constituents to	90S preribosome	`GO:0030686` GO:0030686 defines the 90S preribosome as containing early-associating ribosomal proteins and associated proteins. `DOI:10.1016/s1097-2765(02)00579-8` Grandi et al. 2002 identified 40S subunit processing factors in early 90S pre-ribosomes.
90S preribosome	participates in	ribosome biogenesis	`GO:0030684` GO:0030684 defines preribosomal complexes as being formed during ribosome biogenesis. `GO:0042254` GO:0042254 is the biological-process term for ribosome biogenesis.

Discussions

CURATION_TODO (OPEN): Resolve exact 90S preribosome RNA, ribosomal-protein, U3-associated-protein, 40S-processing-factor and SSU-processome boundaries. GO:0030686 defines a budding-yeast 90S preribosome with 35S pre-rRNA, U3 snoRNA, early-associating ribosomal proteins and associated proteins. The exact source-neutral RNA and protein-family groundings, plus the distinction between the GO:0030686 90S preribosome and the related GO:0032040 small-subunit processome sibling, need a narrower literature-backed curation pass.

Evidence

GO:0030686 Gene Ontology cellular-component term for the 90S preribosome.
GO:0030684 Gene Ontology cellular-component parent term for preribosomal complexes.
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 35S pre-rRNA.
PMID:12150911 PubMed identifier for Grandi et al. 2002, '90S pre-ribosomes include the 35S pre-rRNA, the U3 snoRNP, and 40S subunit processing factors but predominantly lack 60S synthesis factors'.
DOI:10.1016/s1097-2765(02)00579-8 DOI for Grandi et al. 2002, Molecular Cell, verified through NCBI E-utilities.
PMID:12957375 Fromont-Racine et al. 2003 review publication cited in the GO:0030686 definition xrefs.
DOI:10.1016/s0378-1119(03)00629-2 DOI for Fromont-Racine et al. 2003, 'Ribosome assembly in eukaryotes', verified through NCBI E-utilities.
PMID:15120992 Granneman and Baserga 2004 review publication cited in the GO:0030686 definition xrefs.
DOI:10.1016/j.yexcr.2004.03.016 DOI for Granneman and Baserga 2004, 'Ribosome biogenesis: of knobs and RNA processing', verified through NCBI E-utilities.

Curation history

2026-09-25T18:59:10Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-25T19:00:45Z codex · EXPANDED_RECORD — Added preribosome parentage, 35S pre-rRNA, U3 snoRNA and 90S-protein-cohort components, a conservative budding-yeast example, ribosome-biogenesis function, GO/PubMed evidence, a nonmechanistic constituent graph and a TODO for exact 90S component boundaries.
2026-09-25T19:12:02Z codex · ADDRESS_REVIEW — Resolved PR #1595 review issue #1596 by citing SO:0002393 in the 90S preribosome evidence and component-boundary discussion and by making the 35S pre-rRNA grounding rationale self-contained.

Source: data/structures/ribonucleoprotein/90s_preribosome.yaml