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e-Article

Structural basis of intron selection by U2 snRNP in the presence of covalent inhibitors.
Document Type
article
Source
Nature communications. 12(1)
Subject
Spliceosomes
Humans
Lactones
Pyrans
Pyrones
Spiro Compounds
Ribonucleoprotein
U2 Small Nuclear
DNA
Cryoelectron Microscopy
Crystallography
X-Ray
Nucleic Acid Conformation
Protein Conformation
Protein Binding
Introns
Models
Molecular
Language
Abstract
Intron selection during the formation of prespliceosomes is a critical event in pre-mRNA splicing. Chemical modulation of intron selection has emerged as a route for cancer therapy. Splicing modulators alter the splicing patterns in cells by binding to the U2 snRNP (small nuclear ribonucleoprotein)-a complex chaperoning the selection of branch and 3' splice sites. Here we report crystal structures of the SF3B module of the U2 snRNP in complex with spliceostatin and sudemycin FR901464 analogs, and the cryo-electron microscopy structure of a cross-exon prespliceosome-like complex arrested with spliceostatin A. The structures reveal how modulators inactivate the branch site in a sequence-dependent manner and stall an E-to-A prespliceosome intermediate by covalent coupling to a nucleophilic zinc finger belonging to the SF3B subunit PHF5A. These findings support a mechanism of intron recognition by the U2 snRNP as a toehold-mediated strand invasion and advance an unanticipated drug targeting concept.