Phenomenon and mechanism of "secondary damage" duringrepair of DNA damage in irradiated mammalian cells

By means of comet assay, a study of kinetics curve of DNA damage repair in irradiated SX-9 cells that came from mouse breast cancer proceeded. It was found that while the initial DNA damages had nearly been repaired, DNA damages arose for the second time, then they were repaired again. As a result, a phenomenon of “secondary damage” was found during the repair of DNA damages in irradiated SX-9 cells. Further research illuminated that 3-aminobenzamide (3AB), which is an inhibitor of poly (ADP-ribose) polymerase, could change the proceeding of “secondary damage”. For this reason it is poasible that there exists some inner relationship between the phenomenon of “secondary damage” and the function of poly(ADP-ribose) polymerase.