Structure of the minor spliceosomal U11 snRNP

Abstract

The minor spliceosome catalyses the excision of U12-dependent introns from pre-mRNAs. These introns are rare, but their removal is critical for cell viability. We obtained a cryo-EM reconstruction of the 13-subunit U11 snRNP complex, revealing structures of U11 snRNA and five minor spliceosome-specific factors. U11 snRNP appears strikingly different from the equivalent major spliceosome U1 snRNP. SNRNP25 and SNRNP35 form a dimer, which specifically recognises U11 snRNA. PDCD7 forms extended helices, which bridge SNRNP25 and SNRNP48, located at the distal ends of the particle. SNRNP48 forms multiple interfaces with U11 snRNP and, together with ZMAT5, are positioned near the 5-end of the U11 snRNA and likely stabilise the binding of the incoming 5SS. Our structure provides mechanistic insights into U12-dependent intron recognition and the evolution of the splicing machinery.