U4 snRNP

GO:0005687 · Ribonucleoprotein · Ribonucleoprotein complex · Proposed

A ribonucleoprotein complex that contains small nuclear RNA U4, a heptameric ring of Sm proteins, as well as several proteins that are unique to the U4 snRNP, most of which remain associated with the U4 snRNA both while the U4 snRNP is free or assembled into the U4/U6 snRNP or into a series of spliceosomal complexes. [GO:0005687]

Synonyms: snRNP U4

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
U4 snRNA	Rna	part of	`SO:0000393`				U4 small nuclear RNA constituent named in the U4 snRNP definition and grounded to the U4 snRNA Sequence Ontology term. `GO:0005687` GO:0005687 defines the U4 snRNP as containing small nuclear RNA U4. `SO:0000393` SO:0000393 is the Sequence Ontology term for U4 snRNA.
Sm protein ring	Protein complex	part of	Reviewed label only (reviewed name; no accession asserted)				Heptameric Sm protein-ring constituent named in the U4 snRNP definition. `GO:0005687` GO:0005687 defines the U4 snRNP as containing a heptameric ring of Sm proteins.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: The U4 snRNP subcomplex is represented in budding-yeast U4/U6.U5 tri-snRNP cryo-EM structures; broader eukaryotic distribution is left for follow-up curation. [DOI:10.1038/nature16940]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Budding-yeast model whose U4 snRNP subcomplex is represented inside U4/U6.U5 tri-snRNP cryo-EM structures. [DOI:10.1038/nature16940]

Mechanism graphs

U4 snRNA and the Sm ring are U4 snRNP constituents (ASSEMBLY)

The U4 snRNP contains U4 small nuclear RNA and a heptameric Sm protein ring; GO:0005687 also names additional U4-specific proteins whose exact family boundaries remain to be resolved.

Subject	Predicate	Object	Evidence
U4 snRNA	contributes constituents to	U4 snRNP	`GO:0005687` GO:0005687 defines the U4 snRNP as containing small nuclear RNA U4.
Sm protein ring	contributes constituents to	U4 snRNP	`GO:0005687` GO:0005687 defines the U4 snRNP as containing a heptameric ring of Sm proteins.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral groundings for the Sm ring, Prp3, Prp4, Prp31 and other U4-specific protein families that form the U4 snRNP. The first GO:0005687 record captures U4 snRNA and the GO-defined Sm ring at coarse granularity. Individual spliceosomal Sm proteins and U4-specific protein-family boundaries should be resolved before splitting this inventory.

Evidence

GO:0005687 Gene Ontology cellular-component term for the U4 snRNP and its exact synonym.
GO:0097525 Gene Ontology cellular-component parent term for spliceosomal snRNP complex.
SO:0000393 Sequence Ontology term for U4 snRNA.
DOI:10.1038/nature14548 Nguyen, Galej, Bai and colleagues 2015, The architecture of the spliceosomal U4/U6.U5 tri-snRNP, Nature.
PMID:26106855 PubMed identifier for Nguyen, Galej, Bai and colleagues 2015 as reported by PubMed.
DOI:10.1038/nature16940 Nguyen, Galej, Bai and colleagues 2016, Cryo-EM structure of the yeast U4/U6.U5 tri-snRNP at 3.7 Angstrom resolution, Nature.
PMID:26829225 PubMed identifier for Nguyen, Galej, Bai and colleagues 2016 as reported by PubMed.

Curation history

2026-09-24T15:11:45Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-24T15:12:31Z codex · EXPANDED_RECORD — Added the GO exact synonym, spliceosomal snRNP parentage, U4 snRNA and Sm-ring components, budding-yeast distribution, Nguyen/Galej/Nagai yeast U4/U6.U5 tri-snRNP cryo-EM evidence, a minimal U4 snRNP constituent graph and a protein-component grounding TODO.
2026-09-24T15:24:10Z codex · ADDRESS_REVIEW — #1501: narrowed the Sm-ring component role to the GO-supported heptameric ring constituent; #1502: reworded the canonical example to make the yeast evidence explicitly tri-snRNP-derived.

Source: data/structures/ribonucleoprotein/u4_snrnp.yaml