Regulation of the cell cycle by p53 after DNA damage in an amphibian cell line

In mammalian cells, the p53 protein is a kev regulator of the cell cycle fo llowing DNA damage. In the present study, we investigated the function of p 53 in the A6 amphibian cell line. Using various specific Xenopus p53 monocl onal antibodies, we showed that Xenopus p53 accumulates after DNA damage, i ncluding gamma and UV irradiation or treatment with adriamycin, Such accumu lation is accompanied by an increase in the apparent molecular weight of th e protein. This change was shown to be the result of a phosphorylation even t that occurs after DNA damage. Accumulation of Xenopus p53 is parallel to a drastic change in the cell cycle distribution. Brief exposure to adriamyc in or gamma irradiation induces reversible growth arrest, whereas long-term exposure to adriamycin leads to apoptosis, Taken together, these results i ndicate that p53 has a similar behaviour in frog cells and mammalian cells, and that it conserves two activities, cell cycle arrest and apoptosis.