The relationship between DNA repair and apoptosis induced by UV irradiation was investigated. HeLa cells were irradiated by UV light to induce apoptosis. Repair synthesis was inhibited within 1 hr after UV irradiation. p53 and poly(ADP-ribose) polymerase were examined as regulating factors which resulted in the inhibition of DNA repair during apoptosis. HeLa cells transfected with p53 showed no remarkable change in apoptotic cell death and DNA repair compaired with HeLa cells, which have reduced amount of p53. HeLa cells were considered to have a p53 independent regulation mechanism inducing apoptosis and DNA repair. In the cell undergoing apoptosis, PARP cleavage occured before the completion of DNA fragmentation N-terminal fragment of PARP cleaved by CPP32 during apoptosis showed effective inhibition of repair synthesis in vitro. PARP cleavage was proposed to regulate the inhibition of DNA repair synthesis during apoptosis.
