U12-type prespliceosome

GO:0071015 · Ribonucleoprotein · Ribonucleoprotein complex · Proposed

A spliceosomal complex that is formed by the cooperative binding of the heterodimeric U11/U12 snRNP to the 5' splice site and the branch point sequence. The U12-type prespliceosome includes many proteins in addition to those found in the U11/U12 heterodimeric snRNPs. Commitment to a given pair of 5' and 3' splice sites occurs at the time of prespliceosome formation. [GO:0071015]

Synonyms: minor prespliceosome; AT-AC prespliceosome; mammalian U12-type spliceosomal complex A; yeast U12-type 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
U11/U12 snRNP	Protein complex	part of	`GO:0034693`				Heterodimeric U11/U12 small nuclear ribonucleoprotein that cooperatively binds the 5-prime splice site and branch point sequence in the U12-type prespliceosome. `GO:0071015` GO:0071015 defines the U12-type prespliceosome as formed by cooperative binding of heterodimeric U11/U12 snRNP to the 5-prime splice site and the branch point sequence. `GO:0034693` GO:0034693 is the Gene Ontology cellular-component term for the U11/U12 snRNP.

Mechanism graphs

U11/U12 snRNP binding defines the U12-type prespliceosome (ASSEMBLY)

The U12-type prespliceosome forms when heterodimeric U11/U12 snRNP cooperatively binds the 5-prime splice site and branch point sequence.

Subject	Predicate	Object	Evidence
U11/U12 snRNP	cooperatively binds splice signals in	U12-type prespliceosome	`GO:0071015` GO:0071015 defines this prespliceosome by cooperative binding of heterodimeric U11/U12 snRNP to the 5-prime splice site and the branch point sequence.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral component boundaries for U12-type prespliceosome proteins beyond the GO-defined U11/U12 snRNP subcomplex. The first GO:0071015 record captures the defining U11/U12 snRNP subcomplex. Additional U12-type prespliceosome proteins should be resolved into exact source-neutral families or subcomplexes before expanding the component list.

Evidence

GO:0071015 Gene Ontology cellular-component term for the U12-type prespliceosome and its GO synonyms.
GO:0071010 Gene Ontology cellular-component parent term for prespliceosome.
GO:0005689 Gene Ontology cellular-component parent term for U12-type spliceosomal complex.
GO:0034693 Gene Ontology cellular-component term for the U11/U12 snRNP.
DOI:10.1101/gad.13.7.851 Frilander and Steitz 1999, a Genes & Development study of the U11 interaction with the 5-prime splice site and the U12 interaction with the branch point during initial recognition of U12-dependent introns.
DOI:10.1515/BC.2005.084 Will and Luehrmann 2005, Splicing of a rare class of introns by the U12-dependent spliceosome, Biological Chemistry.

Curation history

2026-09-24T23:12:08Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-24T23:13:49Z codex · EXPANDED_RECORD — Added GO exact and narrow synonyms, prespliceosome and U12-type spliceosomal-complex parentage, the GO-grounded U11/U12 snRNP component, Frilander/Steitz and Will/Luehrmann U12-spliceosome evidence, a minimal U11/U12 binding graph and a protein-component grounding TODO.
2026-09-24T23:26:03Z codex · ADDRESS_REVIEW — #1533: clarified the Frilander/Steitz evidence note so the U11 5-prime-splice-site interaction and U12 branch-point interaction are spelled out instead of compressed into slash shorthand.

Source: data/structures/ribonucleoprotein/u12_type_prespliceosome.yaml