Mechanism of auto-inhibition and activation of Mec1ATR checkpoint kinase

DOI: 10.1038/s41594-020-00522-0

Authors: Elias A. Tannous (Washington University School of Medicine) , Luke A. Yates (Imperial College London) , Xiaodong Zhang (Imperial College London) , Peter M. Burgers (Washington University School of Medicine)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nature Structural & Molecular Biology , VOL 149

State: Published (Approved)
Published: November 2020
Diamond Proposal Number(s): 19865

Abstract: In response to DNA damage or replication fork stalling, the basal activity of Mec1ATR is stimulated in a cell-cycle-dependent manner, leading to cell-cycle arrest and the promotion of DNA repair. Mec1ATR 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 Mg2+-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.

Journal Keywords: Biochemistry; Genetics; Molecular biology; Structural biology

Subject Areas: Biology and Bio-materials, Chemistry

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