The Mec1/ATR-induced checkpoint regulates the Rdh54DNA translocase in response to chromosome breaks in yeast

Saccharomyces cerevisiae cells with a single double-strand break (DSB) activate the ATR/Mec1-dependent checkpoint response as a consequence of extensive ssDNA accumulation. The recombination factor Rdh54, a member of the Swi/Sfn2 family of helicase-like proteins, has been implicated in chromatin remodeling and is required for adaptation from a G2/M arrest induced by an unrepaired DSB. Here we show that both the ATR/Mec1 and Chk2/Rad53 kinases phosphorylate Rdh54 protein in the presence of DNA damage, suggesting that the protein is regulated during the DNA damage response. ATR/Mec1 activity is required for Rdh54 localization to a DSB. We will present additional genetic and biochemical evidences on the physiological role of the phosphorylation modification and the role of Rad51 in this. Our results will be considered in the context of cellular regulatory networks that coordinate the checkpoint response and recombination process in the presence of DSB lesions.