U2 snRNP

GO:0005686 · Ribonucleoprotein · Ribonucleoprotein complex · Proposed

A ribonucleoprotein complex that contains small nuclear RNA U2, a heptameric ring of Sm proteins, as well as several proteins that are unique to the U2 snRNP, most of which remain associated with the U2 snRNA both while the U2 snRNP is free or assembled into a series of spliceosomal complexes. [GO:0005686]

Synonyms: snRNP U2; 17S U2 snRNP

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
U2 snRNA	Rna	part of	`SO:0000392`				U2 small nuclear RNA constituent named in the U2 snRNP definition and grounded to the U2 snRNA Sequence Ontology term. `GO:0005686` GO:0005686 defines the U2 snRNP as containing small nuclear RNA U2. `SO:0000392` SO:0000392 is the Sequence Ontology term for U2 snRNA.
Sm protein ring	Protein complex	part of	Reviewed label only (reviewed name; no accession asserted)				Heptameric Sm protein-ring constituent named in the U2 snRNP definition. `GO:0005686` GO:0005686 defines the U2 snRNP as containing a heptameric ring of Sm proteins.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: The U2 snRNP subcomplex is represented in a budding-yeast pre-catalytic B-complex spliceosome cryo-EM structure; broader eukaryotic distribution is left for follow-up curation. [DOI:10.1038/nature22799]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Budding-yeast model whose U2 snRNP subcomplex is represented inside a pre-catalytic B-complex spliceosome cryo-EM structure. [DOI:10.1038/nature22799]

Mechanism graphs

U2 snRNA and the Sm ring are U2 snRNP constituents (ASSEMBLY)

The U2 snRNP contains U2 small nuclear RNA and a heptameric Sm protein ring; GO:0005686 also names additional U2-specific proteins whose exact family boundaries remain to be resolved.

Subject	Predicate	Object	Evidence
U2 snRNA	contributes constituents to	U2 snRNP	`GO:0005686` GO:0005686 defines the U2 snRNP as containing small nuclear RNA U2.
Sm protein ring	contributes constituents to	U2 snRNP	`GO:0005686` GO:0005686 defines the U2 snRNP as containing a heptameric ring of Sm proteins.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral groundings for the Sm ring, SF3a, SF3b and U2-specific protein families that form the U2 snRNP. The first GO:0005686 record captures U2 snRNA and the GO-defined Sm ring at coarse granularity. Individual spliceosomal Sm proteins, SF3a, SF3b and U2-specific protein-family boundaries should be resolved before splitting this inventory.

Evidence

GO:0005686 Gene Ontology cellular-component term for the U2 snRNP and its synonyms.
GO:0097525 Gene Ontology cellular-component parent term for spliceosomal snRNP complex.
SO:0000392 Sequence Ontology term for U2 snRNA.
DOI:10.1038/nature22799 Plaschka, Lin and Nagai 2017, Structure of a pre-catalytic spliceosome, Nature.
PMID:28530653 PubMed identifier for Plaschka, Lin and Nagai 2017 as reported by PubMed.

Curation history

2026-09-24T16:53:28Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-24T16:54:32Z codex · EXPANDED_RECORD — Added the GO exact synonym, spliceosomal snRNP parentage, U2 snRNA and Sm-ring components, budding-yeast B-complex evidence, a minimal U2 snRNP constituent graph and a protein-component grounding TODO.
2026-09-24T17:04:27Z codex · ADDRESS_REVIEW — #1509: added the 17S U2 snRNP narrow synonym exposed by GO:0005686 and broadened the GO evidence note to cover exact and narrow GO synonymy.

Source: data/structures/ribonucleoprotein/u2_snrnp.yaml