Journal: Nat Struct Mol Biol / Year: 2021 Title: Mechanism of auto-inhibition and activation of Mec1 checkpoint kinase. Authors: Elias A Tannous / Luke A Yates / Xiaodong Zhang / Peter M Burgers / Abstract: In response to DNA damage or replication fork stalling, the basal activity of Mec1 is stimulated in a cell-cycle-dependent manner, leading to cell-cycle arrest and the promotion of DNA repair. Mec1 ...In response to DNA damage or replication fork stalling, the basal activity of Mec1 is stimulated in a cell-cycle-dependent manner, leading to cell-cycle arrest and the promotion of DNA repair. Mec1 dysfunction leads to cell death in yeast and causes chromosome instability and embryonic lethality in mammals. Thus, ATR is a major target for cancer therapies in homologous recombination-deficient cancers. Here we identify a single mutation in Mec1, conserved in ATR, that results in constitutive activity. Using cryo-electron microscopy, we determine the structures of this constitutively active form (Mec1(F2244L)-Ddc2) at 2.8 Å and the wild type at 3.8 Å, both in complex with Mg-AMP-PNP. These structures yield a near-complete atomic model for Mec1-Ddc2 and uncover the molecular basis for low basal activity and the conformational changes required for activation. Combined with biochemical and genetic data, we discover key regulatory regions and propose a Mec1 activation mechanism.
History
Deposition
May 19, 2020
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Header (metadata) release
Nov 11, 2020
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Map release
Nov 11, 2020
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Update
Jan 27, 2021
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Current status
Jan 27, 2021
Processing site: PDBe / Status: Released
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Structure visualization
Movie
Surface view with section colored by density value
Model: UltrAuFoil / Material: GOLD / Mesh: 300 / Support film - Material: CARBON / Support film - topology: LACEY / Pretreatment - Type: PLASMA CLEANING / Pretreatment - Atmosphere: AIR
Vitrification
Cryogen name: ETHANE / Chamber humidity: 95 % / Instrument: FEI VITROBOT MARK IV
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Electron microscopy
Microscope
TFS KRIOS
Image recording
Film or detector model: FEI FALCON III (4k x 4k) / Detector mode: INTEGRATING / Digitization - Dimensions - Width: 4096 pixel / Digitization - Dimensions - Height: 4096 pixel / Number grids imaged: 1 / Number real images: 15097 / Average exposure time: 0.5 sec. / Average electron dose: 58.5 e/Å2 Details: ~2/3 of the data were collected at -30 degree stage tilt
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
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