PP2A-B56 epsilon complex is involved in dephosphorylation of gamma-H2AX in the repair process of CPT-induced DNA double-strand breaks

摘要

Phosphorylation of histone H2AX (gamma-H2AX) in response to DNA double-strand breaks (DSBs) should be eliminated from the sites of DNA damage to fulfill the DNA repair and release cells from the growth arrest. Previous study showed that protein phosphatase 2A (PP2A) interact with gamma-H2AX that lead to the dephosphorylation of gamma-H2AX. Here, we examined the effects of suppression of PP2A regulatory subunits on dephosphorylation of gamma-H2AX in human embryonic kidney epithelial cells (HEK) treated by topoisomerase I inhibitor camptothecin (CPT). We found that cells with suppression of B55 alpha or B56 epsilon were more sensitive to DNA damage agents. Suppression of B56 epsilon led to persistence of gamma-H2AX, resulting in prolonged DSBs repair and increased chromatin instability measured by comet assay. In addition, the deficiency of B56 epsilon impaired the cell cycle regulation and the DNA repair pathway of homologous recombination (HR). Notably, we detected that PP2A B56 epsilon subunit was involved directly in dephosphorylation of gamma-H2AX and translocated from cytoplasm to nucleus upon the treatment of CPT. Our findings demonstrate that PP2A holoenzyme containing B56 epsilon is responsible for the dephosphorylation of gamma-H2AX and regulation of DNA repair of DSBs induced by CPT. (C) 2015 Elsevier Ireland Ltd. All rights reserved.