Abstract: γH2AX, 53BP1 and RAD51 foci are the evaluation markers of DNA double strand breaks (DSBs). Above all, γH2AX foci analysis is the most widely used, but recent studies have found that it is not completely consistent with DSBs damage. This study systematically analyzed the dynamic changes of γH2AX, 53BP1 and RAD51 foci during DNA damage and their reasonable application in DSBs damage assessment. According to the results, γH2AX and 53BP1 foci were highly consistent after cells exposed to ionizing radiation treatment, they both could reflect accurately the dynamic changes of DSBs damages and repairs; while RAD51 foci only appeared in part of damaged cells, which was consistent with its role mainly involved in homologous recombination process. Upon treatment with Camptothecin (CPT), γH2AX presented two types of staining (bright and discrete foci and pan-nuclear phosphorylation), while 53BP1 foci only appeared in cells with bright and discrete γH2AX foci and were highly consistent with γH2AX foci. These results revealed that positive staining of γH2AX alone cannot accurately represent DSBs damage, and the extent of DSBs damage should be comprehensively analyzed by combining with staining of 53BP1. The RAD51 foci analysis only reflect the DSBs damage repair of part cells, mainly homologous recombination repair. 

Key words: DNA double-stand breaks, DNA damage repair, ionize radiation, γH2AX