GAMMA-IRRADIATION-INDUCED MICRONUCLEI FROM MOUSE HEPATOMA-CELLS ACCUMULATE HIGH-LEVELS OF THE TUMOR-SUPPRESSOR PROTEIN P53

The p53 tumor suppressor protein plays an important role in the G(1), arrest of cells treated with DNA-damaging agents. Mouse hepatoma cells with wild-type or mutated p53 genotype mere gamma-irradiated and the time course of p53 expression was determined by immunocytochemical sta ining. In p53 wild-type cells, gamma-irradiation led to a transient ac cumulation of the protein in the nuclei, whereas no such accumulation occurred in p53-mutated cells. Micronuclei were induced by gamma-irrad iation in both wild-type and mutated cells in a dose- and time-depende nt manner, but only micronuclei from p53 wild-type cells demonstrated a strongly positive staining reaction for p53 protein. This accumulati on of p53 protein in micronuclei was not associated with a block in DN A synthesis as evidenced by bromodeoxyuridine labeling experiments.