An Atomic Structure of the Human Spliceosome

• Published in: Cell 2017-05, Vol.169 (5), p.918-929.e14
• Main Authors: Zhang, Xiaofeng, Yan, Chuangye, Hang, Jing, Finci, Lorenzo I., Lei, Jianlin, Shi, Yigong
• Format: Article
• Language: English
• Subjects: atomic structure; Base Sequence; cryo-EM; Cryoelectron Microscopy; C∗ complex; DEAD-box RNA Helicases - metabolism; EJC; exon junction complex; exon ligation; Exons; human spliceosome; Humans; Introns; Models, Molecular; pre-mRNA splicing; RNA Precursors - metabolism; RNA Splicing; RNA Splicing Factors - metabolism; RNA-Binding Proteins - metabolism; Saccharomyces cerevisiae - chemistry; Spliceosomes - chemistry; Spliceosomes - metabolism; Spliceosomes - ultrastructure; step 2 factors; step II activated spliceosome
• ISSN: 0092-8674; 1097-4172
• DOI: 10.1016/j.cell.2017.04.033

Mechanistic understanding of pre-mRNA splicing requires detailed structural information on various states of the spliceosome. Here we report the cryo electron microscopy (cryo-EM) structure of the human spliceosome just before exon ligation (the C∗ complex) at an average resolution of 3.76 Å. The splicing factor Prp17 stabilizes the active site conformation. The step II factor Slu7 adopts an extended conformation, binds Prp8 and Cwc22, and is poised for selection of the 3′-splice site. Remarkably, the intron lariat traverses through a positively charged central channel of RBM22; this unusual organization suggests mechanisms of intron recruitment, confinement, and release. The protein PRKRIP1 forms a 100-Å α helix linking the distant U2 snRNP to the catalytic center. A 35-residue fragment of the ATPase/helicase Prp22 latches onto Prp8, and the quaternary exon junction complex (EJC) recognizes upstream 5′-exon sequences and associates with Cwc22 and the GTPase Snu114. These structural features reveal important mechanistic insights into exon ligation. [Display omitted] •The first atomic structure of a human spliceosome•The conformation of the spliceosome just prior to exon ligation•Mechanistic insights on Prp17, Slu7, PRKRIP1, and the EJC•Intron interlocked with RBM22 suggests mechanisms of intron recruitment and release The first atomic structure of human spliceosome reveals important insights into exon ligation.