U1 snRNP

GO:0005685 · Ribonucleoprotein · Ribonucleoprotein complex · Proposed

A ribonucleoprotein complex that contains small nuclear RNA U1, a heptameric ring of Sm proteins, as well as several proteins that are unique to the U1 snRNP, most of which remain associated with the U1 snRNA both while the U1 snRNP is free or assembled into a series of spliceosomal complexes. [GO:0005685]

Synonyms: snRNP U1

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
U1 snRNA	Rna	part of	`SO:0000391`				U1 small nuclear RNA constituent named in the U1 snRNP definition and grounded to the U1 snRNA Sequence Ontology term. `GO:0005685` GO:0005685 defines the U1 snRNP as containing small nuclear RNA U1. `SO:0000391` SO:0000391 is the Sequence Ontology term for U1 snRNA.
Sm protein ring	Protein complex	part of	Reviewed label only (reviewed name; no accession asserted)				Heptameric Sm protein-ring constituent named in the U1 snRNP definition. `GO:0005685` GO:0005685 defines the U1 snRNP as containing a heptameric ring of Sm proteins.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: A Saccharomyces cerevisiae U1 snRNP cryo-EM structure was reported by Li, Liu, Jiang and colleagues; broader eukaryotic distribution is left for follow-up curation. [DOI:10.1038/s41467-017-01241-9]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Budding-yeast model represented in the Li, Liu, Jiang and colleagues U1 snRNP cryo-EM structure. [DOI:10.1038/s41467-017-01241-9]

Mechanism graphs

U1 snRNA and the Sm ring are U1 snRNP constituents (ASSEMBLY)

The U1 snRNP contains U1 small nuclear RNA and a heptameric Sm protein ring; GO:0005685 also states that additional U1-specific proteins are present, with exact family boundaries still to be resolved.

Subject	Predicate	Object	Evidence
U1 snRNA	contributes constituents to	U1 snRNP	`GO:0005685` GO:0005685 defines the U1 snRNP as containing small nuclear RNA U1.
Sm protein ring	contributes constituents to	U1 snRNP	`GO:0005685` GO:0005685 defines the U1 snRNP as containing a heptameric ring of Sm proteins.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral groundings for the Sm ring and U1-specific protein families that form the U1 snRNP. The first GO:0005685 record captures U1 snRNA and the GO-defined Sm ring at coarse granularity. Individual spliceosomal Sm proteins and U1-specific protein-family boundaries should be resolved before splitting this inventory.

Evidence

GO:0005685 Gene Ontology cellular-component term for the U1 snRNP and its exact synonym.
GO:0097525 Gene Ontology cellular-component parent term for spliceosomal snRNP complex.
SO:0000391 Sequence Ontology term for U1 snRNA.
DOI:10.1038/s41467-017-01241-9 Li, Liu, Jiang and colleagues 2017, CryoEM structure of Saccharomyces cerevisiae U1 snRNP offers insight into alternative splicing, Nature Communications.
PMID:29051543 PubMed identifier for Li, Liu, Jiang and colleagues 2017 as reported by PubMed.

Curation history

2026-09-24T15:43:53Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-24T15:44:31Z codex · EXPANDED_RECORD — Added the GO exact synonym, spliceosomal snRNP parentage, U1 snRNA and Sm-ring components, budding-yeast distribution, Li/Liu/Jiang yeast U1 snRNP cryo-EM evidence, a minimal U1 snRNP constituent graph and a protein-component grounding TODO.
2026-09-24T15:56:00Z codex · ADDRESS_REVIEW — #1504: reworded the U1 graph so GO:0005685 supports the presence, not the identities, of additional U1-specific proteins; #1505: narrowed the yeast U1 cryo-EM notes to avoid implying complete protein-boundary resolution.

Source: data/structures/ribonucleoprotein/u1_snrnp.yaml