抄録
Phosphorylation of H2AX (γH2AX) is induced by various genotoxic stresses and associated with the recruitment of damage-signaling factors to damaged DNA. Deletion of H2AX causes hypersensitivity to ionizing radiation (IR), a G2/M checkpoint defect and genomic instability in mice. However, the precise role for γH2AX in DNA repair is less understood. To investigate the role for gH2AX in DNA repair, we generated a mutant line incapable of H2AX phosphorylation by introducing a H2AX mutant allele in which serine 139 is replaced by alanine (S139A) into H2AX+/- cells. In the mutant, phosphorylation of H2AX is abolished after IR. The mutant was sensitive to camptothecin (CMP), which efficiently induces replication blocks, and ionizing radiation (IR). Interestingly, the mutant showed reduced gene targeting frequencies and an impaired Rad51 focus formation, indicating a requirement of γH2AX for homologous recombination (HR). In addition, in a XRCC3-/-/H2AX-/S139A double mutant, spontaneous and CMP-induced chromosomal aberrations, probably caused by defective HR, synergistically increased in number. These results suggest that γH2AX participates in HR-mediated repair during replication, thus maintaining the genomic stability in vertebrates.
