Fig. 6.

ATM/ATR pathways regulate HR and NHEJ in response to oxidative DNA damage. DSBs can be resected by DNA nuclease, generating RPA-coated ssDNA. Rad51-coated filaments invade the homologous strand and strand synthesis continues to form the D loop. The Double Holliday junctions are resolved to generate crossover or non-crossover products. The Ku complex (KU70/Ku80) is bound to both DSB ends with the absence of homologous chromosome in the NHEJ pathway. The Ku complex is also regulated by ATM/ATR. Subsequently, the DSB ends are processed by the catalytic subunits of DNA-PK (DNA-PKcs) and the broken ends of DSB are finally ligated. The MRN complex at the site of DSB may be phosphorylated by ATM/ATR, whereas ATM may also regulate Rad51