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3.9 Å structure of the yeast Mec1-Ddc2 complex, a homolog of human ATR-ATRIP

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Science  01 Dec 2017:
Vol. 358, Issue 6367, pp. 1206-1209
DOI: 10.1126/science.aan8414

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Holding a master regulator in check

A family of eukaryotic protein kinases, the phosphatidylinositol 3-kinase-related kinases (PIKKs), has key functions in DNA repair and nutrient sensing. In humans, ATR kinase locates DNA damage through its partner, ATRIP. Once activated, ATR initiates a cell-cycle cascade that culminates in cell-cycle arrest. Wang et al. determined the high-resolution structure of Mec1-Ddc2 (the yeast homolog of ATR-ATRIP) by electron microscopy. The structure shows the detailed architecture of the multidomain complex that overall forms a dimer of heterodimers. The detailed analysis of the structure reveals how an allosteric mechanism may activate the kinase.

Science, this issue p. 1206

Abstract

The ataxia telangiectasia–mutated and Rad3-related (ATR) kinase is a master regulator of DNA damage response and replication stress in humans, but the mechanism of its activation remains unclear. ATR acts together with its partner ATRIP. Using cryo–electron microscopy, we determined the structure of intact Mec1-Ddc2 (the yeast homolog of ATR-ATRIP), which is poised for catalysis, at a resolution of 3.9 angstroms. Mec1-Ddc2 forms a dimer of heterodimers through the PRD and FAT domains of Mec1 and the coiled-coil domain of Ddc2. The PRD and Bridge domains in Mec1 constitute critical regulatory sites. The activation loop of Mec1 is inhibited by the PRD, revealing an allosteric mechanism of kinase activation. Our study clarifies the architecture of ATR-ATRIP and provides a structural framework for the understanding of ATR regulation.

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