Rpd3L Contributes to the DNA Damage Sensitivity of Saccharomyces cerevisiae Checkpoint Mutants

DNA replication forks that are stalled by DNA damage activate an S phase checkpoint that prevents irreversible fork arrest and cell death. The increased cell death caused by DNA damage in budding yeast cells lacking the Rad53 checkpoint protein kinase is partially suppressed by deletion of the EXO1 gene. Here,we identified that loss of the histone deacetylase complex Rpd3L promotes survival of rad53∆ cells exposed to DNA damaging agents. From epistasis analysis, we show that this suppression operates in a separate pathway from the previously described suppression by deletion of EXO1. The whole sequence of Saccharomyces cerevisiae suppressors of the MMS sensitivity of rad53Δ checkpoint mutants was compared to wild-type controls.