Abstract
In budding yeast, a single DNA double-strand break (DSB) triggers the activation of Mec1ATR-dependent DNA damage checkpoint. After about 12 h, cells turn off the checkpoint signaling and adapt despite the persistence of the DSB. We report that the adaptation involves the autophosphorylation of Mec1 at site S1964. A non-phosphorylatable mec1-S1964A mutant causes cells to arrest permanently in response to a single DSB without affecting the initial kinase activity of Mec1. Autophosphorylation of S1964 is dependent on Ddc1Rad9 and Dpb11TopBP1, and it correlates with the timing of adaptation. We also report that Mec1’s binding partner, Ddc2ATRIP, is an inherently stable protein that is degraded specifically upon DNA damage. Ddc2 is regulated extensively through phosphorylation, which, in turn, regulates the localization of the Mec1-Ddc2 complex to DNA lesions. Taken together, these results suggest that checkpoint response is regulated through the autophosphorylation of Mec1 kinase and through the changes in Ddc2 abundance and phosphorylation.
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•Mec1 is autophosphorylated on S1964 after DNA damage•Mec1-S1964 autophosphorylation correlates with adaptation to DNA damage•Mec1’s binding partner Ddc2 is degraded at the later stages of cell cycle arrest•Ddc2 degradation and Mec1-S1964-P both contribute to checkpoint inactivation
Mec1ATR kinase and its binding partner Ddc2ATRIP orchestrate the DNA damage response in budding yeast. In this paper, Memisoglu et al. demonstrate that the inactivation of the DNA damage checkpoint and resumption of cell cycle progression involves both Mec1 autophosphorylation and Ddc2 degradation.