CONFORMATIONAL EFFECTS IN THE P53 PROTEIN OF MUTATIONS INDUCED DURINGCHEMICAL CARCINOGENESIS - MOLECULAR DYNAMIC AND IMMUNOLOGICAL ANALYSES

The tumor suppressor gene p53 has been identified as the most frequent target of genetic alterations in human cancers. Vinyl chloride, a kno wn human carcinogen that induces the rare sentinel neoplasm angiosarco ma of the liver, has been associated with specific A-->T transversions at the first base of codons 249 and 255 of the p53 gene. These mutati ons result in an Arg-->Trp amino acid substitution at residue 249 and an Ile-->Phe amino acid substitution at residue 255 in a highly conser ved region in the DNA-binding core domain of the p53 protein. To deter mine the effects of these substitutions on the three-dimensional struc ture of the p53 protein, we have performed molecular dynamics calculat ions on this core domain of the wild-type and the Trp-249 and Phe-255 mutants to compute the average structures of each of the three forms. Comparisons of the computed average structures show that both mutants differ substantially from the wild-type structure in certain common, d iscrete regions. One of these regions (residues 204-217) contains the epitope for the monoclonal antibody PAb240, which is concealed in the wild-type structure but accessible in both mutant structures. In order to confirm this conformational shift, tumor tissue and serum from vin yl chloride-exposed individuals with angiosarcomas of the liver were e xamined by immunohistochemistry and enzyme-linked immunosorbent assay. Individuals with tumors that contained the p53 mutations were found t o have detectable mutant p53 protein in their tumor tissue and serum, whereas individuals with tumors without mutations and normal controls did not.