title: Structure of a yeast activated spliceosome at 3.5 Å resolution.
abstract: Pre-messenger RNA (pre-mRNA) splicing is carried out by the spliceosome, which undergoes an intricate assembly and activation process. Here, we report an atomic structure of an activated spliceosome (known as the B(act) complex) from Saccharomyces cerevisiae, determined by cryo-electron microscopy at an average resolution of 3.52 angstroms. The final refined model contains U2 and U5 small nuclear ribonucleoprotein particles (snRNPs), U6 small nuclear RNA (snRNA), nineteen complex (NTC), NTC-related (NTR) protein, and a 71-nucleotide pre-mRNA molecule, which amount to 13,505 amino acids from 38 proteins and a combined molecular mass of about 1.6 megadaltons. The 5' exon is anchored by loop I of U5 snRNA, whereas the 5' splice site (5'SS) and the branch-point sequence (BPS) of the intron are specifically recognized by U6 and U2 snRNA, respectively. Except for coordination of the catalytic metal ions, the RNA elements at the catalytic cavity of Prp8 are mostly primed for catalysis. The catalytic latency is maintained by the SF3b complex, which encircles the BPS, and the splicing factors Cwc24 and Prp11, which shield the 5' exon-5'SS junction. This structure, together with those determined earlier, outlines a molecular framework for the pre-mRNA splicing reaction.
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: D020134:Catalytic Domain; D020285:Cryoelectron Microscopy; D005091:Exons; D007438:Introns; D012322:RNA Precursors / Q000737:chemistry; D012326:RNA Splicing; D000072260:RNA Splicing Factors / Q000737:chemistry*; D012342:RNA, Small Nuclear / Q000737:chemistry; D016601:RNA-Binding Proteins / Q000737:chemistry; D017415:Ribonucleoprotein, U5 Small Nuclear / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000737:chemistry*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry; D017381:Spliceosomes / Q000737:chemistry*
chemical_list: C068835:PRP11 protein, S cerevisiae; D012322:RNA Precursors; D000072260:RNA Splicing Factors; D012342:RNA, Small Nuclear; D016601:RNA-Binding Proteins; D017415:Ribonucleoprotein, U5 Small Nuclear; D029701:Saccharomyces cerevisiae Proteins; C405484:U2 small nuclear RNA; C405485:U5 small nuclear RNA; C405486:U6 small nuclear RNA