Lsm2-8 complex

GO:0120115 · Ribonucleoprotein · Multiprotein complex · Proposed

Heteroheptameric Sm-like protein ring complex composed of Lsm2, Lsm3, Lsm4, Lsm5, Lsm6, Lsm7 and Lsm8 or their orthologs that associates with U6-family spliceosomal snRNAs. [GO:0120115]

Part of: U6 snRNP (GO:0005688); U6atac snRNP (GO:0005691)

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
Lsm2-8 proteins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)			UNKNOWN	Sm-like protein constituents that form the Lsm2-8 heteroheptameric ring in U6-family spliceosomal snRNPs. `GO:0120115` GO:0120115 defines the Lsm2-8 complex as the heteroheptameric complex composed of Lsm2, Lsm3, Lsm4, Lsm5, Lsm6, Lsm7 and Lsm8 or their orthologs. `DOI:10.1038/nature16940` Nguyen, Galej, Bai and colleagues 2016 resolved budding-yeast U4/U6.U5 tri-snRNP particles containing the U6-associated Lsm2-8 ring.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Budding-yeast U6 snRNPs carry an Lsm2-8 ring that is represented inside U4/U6.U5 tri-snRNP cryo-EM structures. [DOI:10.1038/nature16940]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Budding-yeast spliceosomal model in which the Lsm2-8 ring is captured as part of cryo-EM U4/U6.U5 tri-snRNP structures. [DOI:10.1038/nature16940]

Functions

U6-family snRNP association — The Lsm2-8 protein ring associates with U6-family spliceosomal snRNAs as a defining protein-ring constituent of U6 and U6atac snRNPs.
- GO:0005688 GO:0005688 names the Lsm2-8 ring as a U6 snRNP constituent.
- GO:0005691 GO:0005691 names the Lsm2-8 ring as a U6atac snRNP constituent.

Mechanism graphs

Lsm2-8 proteins form a U6-family snRNP ring (ASSEMBLY)

Seven Sm-like Lsm proteins form the GO-defined Lsm2-8 complex, which is a protein-ring constituent of U6 and U6atac snRNPs.

Subject	Predicate	Object	Evidence
Lsm2-8 proteins	assemble into	Lsm2-8 complex	`GO:0120115` GO:0120115 defines the subunit scope of the Lsm2-8 complex.
Lsm2-8 complex	contributes constituents to	U6 snRNP	`GO:0005688` GO:0005688 defines the U6 snRNP as containing the Lsm2-8 heptameric ring complex. `GO:0120115` GO:0120115 is the Gene Ontology cellular-component term for the Lsm2-8 complex.
Lsm2-8 complex	contributes constituents to	U6atac snRNP	`GO:0005691` GO:0005691 defines the U6atac snRNP as containing the Lsm2-8 heptameric ring complex. `GO:0120115` GO:0120115 is the Gene Ontology cellular-component term for the Lsm2-8 complex.

Discussions

INTERPRETATION (RESOLVED): Keep the Lsm2-8 protein ring distinct from complete U6-family snRNPs and from individual Lsm proteins. GO:0120115 denotes the heteroheptameric Lsm2-8 protein complex, whereas GO:0005688 and GO:0005691 denote complete U6 and U6atac small nuclear ribonucleoprotein complexes that contain snRNA and additional proteins.
CURATION_TODO (OPEN): Resolve exact source-neutral groundings for the individual Lsm2, Lsm3, Lsm4, Lsm5, Lsm6, Lsm7 and Lsm8 protein families. GO:0120115 establishes the seven named Sm-like subunits of the Lsm2-8 complex, but this first child-complex record keeps them as a reviewed-label-only aggregate instead of guessing exact InterPro, Pfam, NCBIfam or UniProtKB groundings for individual Lsm proteins.

Evidence

GO:0120115 Gene Ontology cellular-component term for the Lsm2-8 complex.
GO:0032991 Gene Ontology cellular-component term for protein-containing complex.
GO:0005688 Gene Ontology cellular-component term for the U6 snRNP.
GO:0005691 Gene Ontology cellular-component term for the U6atac snRNP.
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.

Curation history

2026-09-30T03:43:31Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-30T03:44:48Z codex · EXPANDED_RECORD — Added protein-complex parentage, U6/U6atac snRNP parthood, a reviewed-label-only Lsm2-8 protein constituent, budding-yeast distribution and canonical example, a U6-family snRNP association function, GO/DOI evidence, a nonmechanistic assembly graph, and boundary and component-grounding discussions.

Source: data/structures/ribonucleoprotein/lsm2_8_complex.yaml