ジャーナル: Nat Struct Mol Biol / 年: 2021 タイトル: Mechanism of auto-inhibition and activation of Mec1 checkpoint kinase. 著者: Elias A Tannous / Luke A Yates / Xiaodong Zhang / Peter M Burgers / 要旨: 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.