National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
GM114178
米国
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
GM071940
米国
National Institutes of Health/National Institute Of Allergy and Infectious Diseases (NIH/NIAID)
AI094386
米国
引用
ジャーナル: Science / 年: 2017 タイトル: Structure of the yeast spliceosomal postcatalytic P complex. 著者: Shiheng Liu / Xueni Li / Lingdi Zhang / Jiansen Jiang / Ryan C Hill / Yanxiang Cui / Kirk C Hansen / Z Hong Zhou / Rui Zhao / 要旨: The spliceosome undergoes dramatic changes in a splicing cycle. Structures of B, B, C, C*, and intron lariat spliceosome complexes revealed mechanisms of 5'-splice site (ss) recognition, branching, ...The spliceosome undergoes dramatic changes in a splicing cycle. Structures of B, B, 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.
The author states the following for the pre-mRNA model building: For regions in the intron or exon where no clear sequence preferences were observed (Spingola et al., PMID 10024174), U, A, U, and A-U are used to represent a generic nucleotide, purine, pyrimidine, and standard Watson-Crick basepair, respectively, based on the EM density. Nucleotides -7 to +7 in the exon are modeled mostly as the preferred nucleotides in each position (Spingola et al. PMID 10024174) unless the density suggests otherwise. Some nucleotides in the intron seem to form basepairs with defined U2 or U6 snRNA sequence based on EM densities, and are modeled as complementary nucleotides to the corresponding U2 or U6 sequence unless the density suggests otherwise.
得られたモデル
PDB-6bk8: S. cerevisiae spliceosomal post-catalytic P complex