Author(s): Chowdhury D, Xu X, Zhong X, Ahmed F, Zhong J,
Abstract Share this page
Abstract The histone H2A variant H2AX is rapidly phosphorylated in response to DNA double-stranded breaks to produce gamma-H2AX. gamma-H2AX stabilizes cell-cycle checkpoint proteins and DNA repair factors at the break site. We previously found that the protein phosphatase PP2A is required to resolve gamma-H2AX foci and complete DNA repair after exogenous DNA damage. Here we describe a three-protein PP4 phosphatase complex in mammalian cells, containing PP4C, PP4R2, and PP4R3beta, that specifically dephosphorylates ATR-mediated gamma-H2AX generated during DNA replication. PP4 efficiently dephosphorylates gamma-H2AX within mononucleosomes in vitro and does not directly alter ATR or checkpoint kinase activity, suggesting that PP4 acts directly on gamma-H2AX in cells. When the PP4 complex is silenced, repair of DNA replication-mediated breaks is inefficient, and cells are hypersensitive to DNA replication inhibitors, but not radiomimetic drugs. Therefore, gamma-H2AX elimination at DNA damage foci is required for DNA damage repair, but accomplishing this task involves distinct phosphatases with potentially overlapping roles.
This article was published in Mol Cell
and referenced in Journal of Cancer Science & Therapy