ABSTRACT A Point Mutation in the p53 Tumor Suppresor Gene in DAOY Cell Line By Luis Lopez
Mutations in the p53 tumor suppressor gene are found frequently in human mammary, colon, and bladder carcinomas. In this study, a brain tumor cell line, DAOY, was evaluated for the presence of similar mutations. Previous analysis of the DAOY genomic DNA has revealed that the human p53 tumor suppressor gene has lost its heterozygosity and that the remaining p53 allele produced p53 mRNA of normal size (Raffel, 1990). To test the possibility that the remaining p53 allele was the target of mutation, a sequence analysis of the evolutionarily highly conserved region of p53 cDNA was carried out and showed that a point mutation of guanine to thymine transition occurs at codon 242. When normal, base 725 is part of a cysteine codon (TG725C); when mutated, it becomes a phenylalanine codon (TT725C). These results have led to a general model of tumorigenesis requiring loss of both alleles at a tumor suppressor locus. This study has also started to test for the effect of expression when a wt-p53 is transfected into DAOY cell line. Among 9 G418-resistant clones screened, 3 showed the right molecular size of cDNA p53 when analyzed by Southern Blotting techniques.