Journal: Nat Struct Mol Biol / Year: 2022 Title: Structural mechanism for the selective phosphorylation of DNA-loaded MCM double hexamers by the Dbf4-dependent kinase. Authors: Julia F Greiwe / Thomas C R Miller / Julia Locke / Fabrizio Martino / Steven Howell / Anne Schreiber / Andrea Nans / John F X Diffley / Alessandro Costa / Abstract: Loading of the eukaryotic replicative helicase onto replication origins involves two MCM hexamers forming a double hexamer (DH) around duplex DNA. During S phase, helicase activation requires MCM ...Loading of the eukaryotic replicative helicase onto replication origins involves two MCM hexamers forming a double hexamer (DH) around duplex DNA. During S phase, helicase activation requires MCM phosphorylation by Dbf4-dependent kinase (DDK), comprising Cdc7 and Dbf4. DDK selectively phosphorylates loaded DHs, but how such fidelity is achieved is unknown. Here, we determine the cryogenic electron microscopy structure of Saccharomyces cerevisiae DDK in the act of phosphorylating a DH. DDK docks onto one MCM ring and phosphorylates the opposed ring. Truncation of the Dbf4 docking domain abrogates DH phosphorylation, yet Cdc7 kinase activity is unaffected. Late origin firing is blocked in response to DNA damage via Dbf4 phosphorylation by the Rad53 checkpoint kinase. DDK phosphorylation by Rad53 impairs DH phosphorylation by blockage of DDK binding to DHs, and also interferes with the Cdc7 active site. Our results explain the structural basis and regulation of the selective phosphorylation of DNA-loaded MCM DHs, which supports bidirectional replication.
History
Deposition
Jul 15, 2021
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Header (metadata) release
Feb 2, 2022
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Map release
Feb 2, 2022
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Update
Jul 17, 2024
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Current status
Jul 17, 2024
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: 90 % / Chamber temperature: 295 K / Instrument: FEI VITROBOT MARK IV / Details: blotted for 3 seconds before plunging.
Details
The entire MCM loading and phosphorylation reaction was applied to the EM grid.
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Electron microscopy
Microscope
FEI TITAN KRIOS
Specialist optics
Energy filter - Name: GIF Bioquantum / Energy filter - Slit width: 20 eV
Image recording
Film or detector model: GATAN K2 SUMMIT (4k x 4k) / Detector mode: COUNTING / Number grids imaged: 1 / Number real images: 18135 / Average exposure time: 9.0 sec. / Average electron dose: 51.3 e/Å2
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
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