Journal: Nat Commun / Year: 2021 Title: Structural basis of intron selection by U2 snRNP in the presence of covalent inhibitors. Authors: Constantin Cretu / Patricia Gee / Xiang Liu / Anant Agrawal / Tuong-Vi Nguyen / Arun K Ghosh / Andrew Cook / Melissa Jurica / Nicholas A Larsen / Vladimir Pena / 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 ...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.
History
Deposition
May 25, 2021
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Header (metadata) release
Aug 4, 2021
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Map release
Aug 4, 2021
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Update
Aug 4, 2021
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Current status
Aug 4, 2021
Processing site: PDBe / Status: Released
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Structure visualization
Movie
Surface view with section colored by density value
Cryogen name: ETHANE / Chamber humidity: 100 % / Chamber temperature: 277.15 K / Instrument: FEI VITROBOT MARK IV Details: The A3'-SSA complex was frozen in vitreous ice by applying ~2.2 uL crosslinked sample to both sides of a glow-discharged UltrAufoil R1.2/1.3 gold grid. The excess sample was blotted away for ...Details: The A3'-SSA complex was frozen in vitreous ice by applying ~2.2 uL crosslinked sample to both sides of a glow-discharged UltrAufoil R1.2/1.3 gold grid. The excess sample was blotted away for 2s using a blot force of 7 and the grid was snap frozen in liquid ethane cooled by liquid nitrogen..
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Electron microscopy
Microscope
FEI TITAN KRIOS
Specialist optics
Energy filter - Name: GIF Quantum LS / Energy filter - Slit width: 20 eV
Image recording
Film or detector model: GATAN K3 (6k x 4k) / Number grids imaged: 1 / Number real images: 10494 / Average exposure time: 2.0 sec. / Average electron dose: 41.41 e/Å2
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
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