ANALYSIS OF THE P53 GENE ALTERATIONS IN MOUSE EMBRYO FIBROBLAST CELL-LINE BALB 3T12 AND ITS DERIVATIVE 312

We have analysed the status of the p53 gene in the mouse embryo fibrob last cell line Balb 3T12 (TD50 = 10(6)) and its transformed clonal der ivative 312 (TD50 = 10(4)) with an aim to determine whether there exis ts a correlation between increased tumorigenicity and clonal expansion of cells bearing a mutation in the p53 gene. While Southern hybridiza tions did not show any obvious changes in the p53 gene organization in 3T12 and 312 cells, sequencing the p53 cDNA revealed that 3T12 is mut ated at the amino acid residue 233 (Tyr --> Asp) whereas 312 is mutate d at: the residue 132 (Cys --> Trp). Exploiting the altered RFLP patte rn due to mutations, we identified that 3T12 contains p53 alleles that are different from the already identified mutant p53. On the basis of these observations, we conclude that 3T12 and 312 have evolved indepe ndently.