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A human postcatalytic spliceosome structure reveals essential roles of metazoan factors for exon ligation
DOI:
10.1126/science.aaw5569
PMID:
30705154
Authors:
Sebastian M.
Fica
(MRC Laboratory of Molecular Biology)
,
Chris
Oubridge
(MRC Laboratory of Molecular Biology)
,
Max E.
Wilkinson
(MRC Laboratory of Molecular Biology)
,
Andrew J.
Newman
(MRC Laboratory of Molecular Biology)
,
Kiyoshi
Nagai
(MRC Laboratory of Molecular Biology)
Co-authored by industrial partner:
No
Type:
Journal Paper
Journal:
Science
, VOL 363
, PAGES 710 - 714
State:
Published (Approved)
Published:
February 2019
Diamond Proposal Number(s):
17434
Abstract: During exon ligation, the Saccharomyces cerevisiae spliceosome recognizes the 3'-splice site (3'SS) of precursor messenger RNA (pre-mRNA) through non-Watson-Crick pairing with the 5'SS and the branch adenosine, in a conformation stabilized by Prp18 and Prp8. Here we present the 3.3-angstrom cryo-electron microscopy structure of a human postcatalytic spliceosome just after exon ligation. The 3'SS docks at the active site through conserved RNA interactions in the absence of Prp18. Unexpectedly, the metazoan-specific FAM32A directly bridges the 5'-exon and intron 3'SS of pre-mRNA and promotes exon ligation, as shown by functional assays. CACTIN, SDE2, and NKAP-factors implicated in alternative splicing-further stabilize the catalytic conformation of the spliceosome during exon ligation. Together these four proteins act as exon ligation factors. Our study reveals how the human spliceosome has co-opted additional proteins to modulate a conserved RNA-based mechanism for 3'SS selection and to potentially fine-tune alternative splicing at the exon ligation stage.
Journal Keywords: cryoEM; splicing; gene expression
Subject Areas:
Biology and Bio-materials,
Chemistry,
Medicine
Diamond Offline Facilities:
Electron Bio-Imaging Centre (eBIC)
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Krios II-Titan Krios II at Diamond