Regulatory phosphosite on Mec1 and control of RNAP11 and PIII during replication stress

Yeast sensor checkpoint kinase Mec1 is phosphorylated at Ser1991 upon HU replication stress. The phospho-accepter mutant (mec1-S1991A) confers HU sensitivity and synthetic sickness with the mutants that aggravate replication and transcription collision. To understand how the entire chromatin proteome (chromatome) responds to replication stress, we first investigated the global chromatin-bound proteins in S-phase yeast cells in the presence and absence of HU. Second, we performed phospho-proteome analysis in wild-type and mec1-S1991A mutant to find the S1991-phospho-dependent targets of Mec1 in the presence and absence of HU. Samples were duplicated in chromatome and triplicated in phospho-proteome analysis.