title: Structure of a yeast step II catalytically activated spliceosome.
abstract: Each cycle of precursor messenger RNA (pre-mRNA) splicing comprises two sequential reactions, first freeing the 5' exon and generating an intron lariat-3' exon and then ligating the two exons and releasing the intron lariat. The second reaction is executed by the step II catalytically activated spliceosome (known as the C* complex). Here, we present the cryo-electron microscopy structure of a C* complex from Saccharomyces cerevisiae at an average resolution of 4.0 angstroms. Compared with the preceding spliceosomal complex (C complex), the lariat junction has been translocated by 15 to 20 angstroms to vacate space for the incoming 3'-exon sequences. The step I splicing factors Cwc25 and Yju2 have been dissociated from the active site. Two catalytic motifs from Prp8 (the 1585 loop and the β finger of the ribonuclease H-like domain), along with the step II splicing factors Prp17 and Prp18 and other surrounding proteins, are poised to assist the second transesterification. These structural features, together with those reported for other spliceosomal complexes, yield a near-complete mechanistic picture on the splicing cycle.
authors.affiliation: Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Chuangye
authors.initials: C
authors.lastname: Yan
authors.affiliation: Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Ruixue
authors.initials: R
authors.lastname: Wan
authors.affiliation: Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Bai
authors.affiliation: Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Gaoxingyu
authors.initials: G
authors.lastname: Huang
authors.affiliation: Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China. shi-lab@tsinghua.edu.cn.
authors.forename: Yigong
authors.initials: Y
authors.lastname: Shi
mesh_terms: D020816:Amino Acid Motifs; D055162:Biocatalysis; D020134:Catalytic Domain; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000648:ultrastructure; D020285:Cryoelectron Microscopy; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000648:ultrastructure; D005091:Exons; D012326:RNA Splicing; D000072260:RNA Splicing Factors / Q000737:chemistry / Q000648:ultrastructure; D017414:Ribonucleoprotein, U4-U6 Small Nuclear / Q000737:chemistry / Q000648:ultrastructure; D017415:Ribonucleoprotein, U5 Small Nuclear / Q000737:chemistry / Q000648:ultrastructure; D012441:Saccharomyces cerevisiae / Q000378:metabolism* / Q000648:ultrastructure*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000648:ultrastructure; D017381:Spliceosomes / Q000737:chemistry* / Q000648:ultrastructure*
chemical_list: C093570:CDC40 protein, S cerevisiae; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C080779:PRP18 protein, S cerevisiae; C077018:PRP8 protein, S cerevisiae; D000072260:RNA Splicing Factors; D017414:Ribonucleoprotein, U4-U6 Small Nuclear; D017415:Ribonucleoprotein, U5 Small Nuclear; D029701:Saccharomyces cerevisiae Proteins