ULTRAVIOLET-INDUCED CELL-DEATH IS INDEPENDENT OF DNA-REPLICATION IN RAT KANGAROO CELLS

Rat kangaroo (Potorous tridactylus) cells have an efficient repair sys tem for photoreactivation of lethal lesions induced by 254 nm UV. Howe ver, this ability is lost with increasing time after UV, being complet ely ineffective after 24 h. Critical events leading to W-induced cell death must occur within this period of time. DNA synthesis was inhibit ed by the DNA polymerase inhibitor aphidicolin and the loss of the cap ability to photorepair lethal lesions was maintained as for replicatin g cells. Similar data were obtained in synchronized cells UV irradiate d immediately before S phase. Under the same conditions, the ability t o remove cyclobutane pyrimidine dimers by photoreactivation in these c ells remained unchanged 24 h after irradiation. These data indicate th at the critical events responsible for UV-induced cell death occur in the absence of DNA replication.