Pwp2p-containing subcomplex of 90S preribosome

GO:0034388 · Other · Multiprotein complex · Proposed

A protein complex that forms a subcomplex of the 90S preribosome and can interact directly with the 5' External Transcribed Spacer (ETS) of the full length pre-rRNA transcript. In S. cerevisiae, it sediments at 25-30 S and is composed of Pwp2p, Dip2p, Utp21p, Utp13p, Utp18p, and Utp6p. [GO:0034388]

Synonyms: 25-30 S subcomplex of 90S preribosome; UTP-B complex

Part of: nucleolus (GO:0005730); 90S preribosome (GO:0030686)

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

Components

Component	Type	Part of / acts on	Grounding	Genes	Essential	Role
Pwp2 UTP-B subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	PWP2	UNKNOWN	Protein constituent of the budding-yeast Pwp2p-containing subcomplex of 90S preribosome / UTP-B complex. `GO:0034388` GO:0034388 defines the Pwp2p-containing subcomplex as containing Pwp2p. `DOI:10.1074/jbc.M404909200` Dosil and Bustelo 2004 identified Pwp2p among the proteins associated with the Pwp2 small subcomplex.
Dip2 UTP-B subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	DIP2	UNKNOWN	Protein constituent of the budding-yeast Pwp2p-containing subcomplex of 90S preribosome / UTP-B complex. `GO:0034388` GO:0034388 defines the Pwp2p-containing subcomplex as containing Dip2p. `DOI:10.1074/jbc.M404909200` Dosil and Bustelo 2004 identified Dip2p among the proteins associated with the Pwp2 small subcomplex.
Utp21 UTP-B subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	UTP21	UNKNOWN	Protein constituent of the budding-yeast Pwp2p-containing subcomplex of 90S preribosome / UTP-B complex. `GO:0034388` GO:0034388 defines the Pwp2p-containing subcomplex as containing Utp21p. `DOI:10.1074/jbc.M404909200` Dosil and Bustelo 2004 identified Utp21p among the proteins associated with the Pwp2 small subcomplex.
Utp13 UTP-B subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	UTP13	UNKNOWN	Protein constituent of the budding-yeast Pwp2p-containing subcomplex of 90S preribosome / UTP-B complex. `GO:0034388` GO:0034388 defines the Pwp2p-containing subcomplex as containing Utp13p. `DOI:10.1074/jbc.M404909200` Dosil and Bustelo 2004 identified Utp13p among the proteins associated with the Pwp2 small subcomplex.
Utp18 UTP-B subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	UTP18	UNKNOWN	Protein constituent of the budding-yeast Pwp2p-containing subcomplex of 90S preribosome / UTP-B complex. `GO:0034388` GO:0034388 defines the Pwp2p-containing subcomplex as containing Utp18p. `DOI:10.1074/jbc.M404909200` Dosil and Bustelo 2004 identified Utp18p among the proteins associated with the Pwp2 small subcomplex.
Utp6 UTP-B subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	UTP6	UNKNOWN	Protein constituent of the budding-yeast Pwp2p-containing subcomplex of 90S preribosome / UTP-B complex. `GO:0034388` GO:0034388 defines the Pwp2p-containing subcomplex as containing Utp6p. `DOI:10.1074/jbc.M404909200` Dosil and Bustelo 2004 identified Utp6p among the proteins associated with the Pwp2 small subcomplex.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Budding yeast is the organism in which the Pwp2p-containing UTP-B subcomplex was defined as a 25-30 S six-protein particle of the 90S preribosome. [GO:0034388]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Dosil and Bustelo 2004 characterized budding-yeast Pwp2 as part of a stable small subcomplex with Dip2, Utp6, Utp13, Utp18 and Utp21. [DOI:10.1074/jbc.M404909200]

Functions

90S preribosome assembly GO:0034463 — The Pwp2p-containing UTP-B subcomplex supports early assembly of 90S preribosomes and can interact directly with the 5' External Transcribed Spacer of 35S pre-rRNA.
- GO:0034388 GO:0034388 defines the Pwp2p-containing complex as a subcomplex of the 90S preribosome.
- GO:0034463 GO:0034463 is the Gene Ontology biological-process term for 90S preribosome assembly.
- DOI:10.1074/jbc.M404909200 Dosil and Bustelo 2004 found that Pwp2 depletion blocks formation of 90S preribosomes and prevents U3 snoRNP and other 90S particle components from associating with 35S pre-rRNA.

Mechanism graphs

UTP-B subunits form a 90S preribosome subcomplex (ASSEMBLY)

In Saccharomyces cerevisiae, Pwp2, Dip2, Utp21, Utp13, Utp18 and Utp6 form a Pwp2p-containing UTP-B subcomplex that is part of the 90S preribosome.

Subject	Predicate	Object	Evidence
Pwp2 UTP-B subunit	contributes to	Pwp2p-containing subcomplex of 90S preribosome	`GO:0034388` GO:0034388 defines Pwp2p as a component of the Pwp2p-containing subcomplex. `DOI:10.1074/jbc.M404909200` Dosil and Bustelo 2004 identified Pwp2p with the Pwp2 small subcomplex.
Dip2 UTP-B subunit	contributes to	Pwp2p-containing subcomplex of 90S preribosome	`GO:0034388` GO:0034388 defines Dip2p as a component of the Pwp2p-containing subcomplex. `DOI:10.1074/jbc.M404909200` Dosil and Bustelo 2004 identified Dip2p with the Pwp2 small subcomplex.
Utp21 UTP-B subunit	contributes to	Pwp2p-containing subcomplex of 90S preribosome	`GO:0034388` GO:0034388 defines Utp21p as a component of the Pwp2p-containing subcomplex. `DOI:10.1074/jbc.M404909200` Dosil and Bustelo 2004 identified Utp21p with the Pwp2 small subcomplex.
Utp13 UTP-B subunit	contributes to	Pwp2p-containing subcomplex of 90S preribosome	`GO:0034388` GO:0034388 defines Utp13p as a component of the Pwp2p-containing subcomplex. `DOI:10.1074/jbc.M404909200` Dosil and Bustelo 2004 identified Utp13p with the Pwp2 small subcomplex.
Utp18 UTP-B subunit	contributes to	Pwp2p-containing subcomplex of 90S preribosome	`GO:0034388` GO:0034388 defines Utp18p as a component of the Pwp2p-containing subcomplex. `DOI:10.1074/jbc.M404909200` Dosil and Bustelo 2004 identified Utp18p with the Pwp2 small subcomplex.
Utp6 UTP-B subunit	contributes to	Pwp2p-containing subcomplex of 90S preribosome	`GO:0034388` GO:0034388 defines Utp6p as a component of the Pwp2p-containing subcomplex. `DOI:10.1074/jbc.M404909200` Dosil and Bustelo 2004 identified Utp6p with the Pwp2 small subcomplex.
Pwp2p-containing subcomplex of 90S preribosome	associates with	35S pre-rRNA 5' External Transcribed Spacer	`GO:0034388` GO:0034388 defines the complex by its direct interaction with the 5' External Transcribed Spacer of the full-length pre-rRNA transcript. `DOI:10.1074/jbc.M404909200` Dosil and Bustelo 2004 reported that the Pwp2 small subcomplex can interact directly with the 5' end of 35S pre-rRNA.
Pwp2p-containing subcomplex of 90S preribosome	part of	90S preribosome	`GO:0034388` GO:0034388 carries a part_of relationship to GO:0030686, the 90S preribosome.
Pwp2p-containing subcomplex of 90S preribosome	supports	90S preribosome assembly	`GO:0034463` GO:0034463 is the process term for 90S preribosome assembly. `DOI:10.1074/jbc.M404909200` Dosil and Bustelo 2004 found that Pwp2 depletion blocks 90S preribosome formation.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral family groundings for the Pwp2, Dip2, Utp21, Utp13, Utp18 and Utp6 constituents of the Pwp2p-containing UTP-B complex. GO:0034388 uses Saccharomyces gene-product names while noting that analogous complexes in other eukaryotes can use the term. Exact cross-eukaryotic InterPro, Pfam, NCBIfam or UniProt family boundaries for the six UTP-B proteins need narrower follow-up curation before these component labels can be grounded.

Evidence

GO:0034388 Gene Ontology cellular-component term for the Pwp2p-containing subcomplex of the 90S preribosome and its exact UTP-B synonyms.
GO:0140513 Gene Ontology cellular-component parent term for nuclear protein-containing complexes.
GO:0005730 Gene Ontology cellular-component term for the nucleolus.
GO:0030686 Gene Ontology cellular-component term for the 90S preribosome.
GO:0034463 Gene Ontology biological-process term for 90S preribosome assembly.
PMID:15231838 PubMed identifier for Dosil and Bustelo 2004, the Journal of Biological Chemistry paper cited by GO:0034388.
DOI:10.1074/jbc.M404909200 DOI for Dosil and Bustelo 2004, 'Functional characterization of Pwp2, a WD family protein essential for the assembly of the 90 S pre-ribosomal particle', verified through NCBI E-utilities.

Curation history

2026-09-25T21:30:04Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-25T21:31:06Z codex · EXPANDED_RECORD — Added UTP-B synonymy, nuclear protein-containing complex parentage, nucleolar and 90S preribosome parthood, six reviewed-label-only UTP-B constituent rows, budding-yeast scope, a 90S-preribosome-assembly function, GO/PubMed/DOI evidence, a nonmechanistic assembly graph, and a UTP-B subunit-grounding TODO.

Source: data/structures/other/pwp2p_containing_subcomplex_of_90s_preribosome.yaml