prespliceosome

GO:0071010 · Ribonucleoprotein · Ribonucleoprotein complex · Proposed

A spliceosomal complex that is formed by association of the 5' splice site and the branch point sequence with specific snRNPs. The prespliceosome includes many proteins in addition to those found in the bound snRNPs. Commitment to a given pair of 5' and 3' splice sites occurs at the time of prespliceosome formation. Prespliceosome complexes are not active for splicing, but are instead an early step in the assembly of a spliceosomal complex. [GO:0071010]

Synonyms: prespliceosomal complex; mammalian spliceosomal complex A; yeast spliceosomal complex B

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
bound prespliceosomal snRNPs	Protein complex	part of	Reviewed label only (reviewed name; no accession asserted)				Small nuclear ribonucleoprotein constituents bound to the 5-prime splice site and branch point sequence in prespliceosomes. `GO:0071010` GO:0071010 defines the prespliceosome as a spliceosomal complex formed by association of the 5-prime splice site and branch point sequence with specific snRNPs. `GO:0071004` GO:0071004 defines the U2-type prespliceosome by association of the 5-prime splice site with U1 snRNP and branch-point-sequence recognition by U2 snRNP. `GO:0071015` GO:0071015 defines the U12-type prespliceosome by cooperative binding of heterodimeric U11/U12 snRNP to the 5-prime splice site and branch point sequence.

Mechanism graphs

Prespliceosomes bind splice signals through specific snRNPs (ASSEMBLY)

Prespliceosomes form when state-specific small nuclear ribonucleoproteins bind the 5-prime splice site and branch point sequence.

Subject	Predicate	Object	Evidence
bound prespliceosomal snRNPs	bind splice signals in	prespliceosome	`GO:0071010` GO:0071010 defines the prespliceosome by association of the 5-prime splice site and branch point sequence with specific snRNPs. `GO:0071004` GO:0071004 grounds the U1 and U2 snRNP-bound major-spliceosome child state. `GO:0071015` GO:0071015 grounds the U11/U12 snRNP-bound minor-spliceosome child state.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral snRNP membership and additional protein boundaries for each prespliceosome subtype. The first GO:0071010 parent record captures only the generic presence of splice-signal-bound snRNP constituents supported by GO. Child records for U2-type and U12-type prespliceosomes should carry the exact U1/U2 and U11/U12 constituent boundaries that apply to those specific states.

Evidence

GO:0071010 Gene Ontology cellular-component term for prespliceosome and its GO synonyms.
GO:0005681 Gene Ontology cellular-component parent term for spliceosomal complex.
GO:0071004 Gene Ontology cellular-component term for the U2-type prespliceosome child state.
GO:0071015 Gene Ontology cellular-component term for the U12-type prespliceosome child state.

Curation history

2026-09-25T07:56:23Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-25T07:56:58Z codex · EXPANDED_RECORD — Added GO exact and narrow synonyms, spliceosomal-complex parentage, a reviewed-label-only state-specific bound snRNP cohort, a conservative prespliceosome binding graph and a TODO for exact U2-type and U12-type prespliceosome boundaries.

Source: data/structures/ribonucleoprotein/prespliceosome.yaml