Structure of the yeast spliceosomal postcatalytic P complex

• Published in: Science (American Association for the Advancement of Science) Vol. 358; no. 6368; pp. 1278 - 1283
• Main Authors: Liu, Shiheng, Li, Xueni, Zhang, Lingdi, Jiang, Jiansen, Hill, Ryan C., Cui, Yanxiang, Hansen, Kirk C., Zhou, Z. Hong, Zhao, Rui
• Format: Journal Article
• Language: English
• Published: United States American Association for the Advancement of Science 08.12.2017; The American Association for the Advancement of Science
• Subjects: Base Pairing; Biocatalysis; Catalytic Domain; Cryoelectron Microscopy; DEAD-box RNA Helicases - chemistry; DEAD-box RNA Helicases - genetics; DEAD-box RNA Helicases - ultrastructure; DNA helicase; Electron microscopy; Exons; Introns; Microscopy; Multienzyme Complexes - chemistry; Multienzyme Complexes - genetics; Multienzyme Complexes - ultrastructure; Mutation; Nucleotides; Protein Conformation; Proteins; Recognition; Ribonucleoprotein, U4-U6 Small Nuclear - chemistry; Ribonucleoprotein, U4-U6 Small Nuclear - genetics; Ribonucleoprotein, U4-U6 Small Nuclear - ultrastructure; Ribonucleoprotein, U5 Small Nuclear - chemistry; Ribonucleoprotein, U5 Small Nuclear - genetics; Ribonucleoprotein, U5 Small Nuclear - ultrastructure; RNA Splice Sites; RNA Splicing; RNA Splicing Factors - chemistry; RNA Splicing Factors - genetics; RNA Splicing Factors - ultrastructure; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - chemistry; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - ultrastructure; Spliceosomes - chemistry; Spliceosomes - ultrastructure; Splicing; Yeast
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.aar3462

The spliceosome undergoes dramatic changes in a splicing cycle. Structures of B, Bact, C, C*, and intron lariat spliceosome complexes revealed mechanisms of 5′–splice site (ss) recognition, branching, and intron release, but lacked information on 3′-ss recognition, exon ligation, and exon release. Here we report a cryo–electron microscopy structure of the postcatalytic P complex at 3.3-angstrom resolution, revealing that the 3′ ss is mainly recognized through non–Watson-Crick base pairing with the 5′ ss and branch point. Furthermore, one or more unidentified proteins become stably associated with the P complex, securing the 3′ exon and potentially regulating activity of the helicase Prp22. Prp22 binds nucleotides 15 to 21 in the 3′ exon, enabling it to pull the intron-exon or ligated exons in a 3′ to 5′ direction to achieve 3′-ss proofreading or exon release, respectively.