Dephosphorylation of γH2A by Gcl7/Protein Phosphatase 1 promotes recovery from inhibition of DNA replication

Replication fork stalling caused by deoxynucleotide depletion triggers Rad53 phosphorylation and checkpoint activation, which plays a crucial role in maintaining functional DNA replication forks. How cells regulate checkpoint deactivation after inhibition of DNA replication is poorly understood. Here, we show that the budding yeast protein phosphatase Glc7/PP1 promotes disappearance of phosphorylated Rad53 and recovery from replication fork stalling caused by hydroxyurea (HU). Glc7 is also required for recovery from a DSB-induced checkpoint, while it is dispensable for checkpoint inactivation during MMS exposure, which instead requires the protein phosphatases Pph3, Ptc2 and Ptc3. Furthermore, Glc7 counteracts histone H2A phosphorylation on serine 129 (γH2A) in vivo and dephosphorylates γH2A in vitro. Finally, the replication recovery defects of HU-treated glc7 mutants are partially rescued by Rad53 inactivation or γH2A formation lack, and the latter also counteracts hyperphosphorylated Rad53 accumulation. We therefore propose that Glc7 activity promotes resumption of DNA replication and that γH2A dephosphorylation is a critical Glc7 function in this process.