UV-INDUCED MUTAGENESIS OF HUMAN P53 IN A VECTOR REPLICATED IN SACCHAROMYCES-CEREVISIAE

Mutation of the p53 tumor suppressor gene is the most common genetic a lteration identified to date in human cancers, Similarities of p53 mut ations found in human cancers with those induced in experimental syste ms have been interpreted as evidence supporting a causative role for e nvironmental carcinogens in certain tumor types, We have developed and validated a method for generation of mutation spectra and measurement of mutation frequency directly on human p53 cDNA in a vector followin g treatment with mutagens and replication in yeast, Mutants that had l ost the DNA binding/transcription activation function of p53 were dete cted by yeast colony color, isolated, and sequenced, UV light was used to characterize and validate the system, and a dose-dependent increas e in mutation frequency was seen following exposure of the plasmid to increasing doses of UV, resulting in an 18-fold increase over the spon taneous frequency (3.2 x 10(-4)) at the highest level tested (300 J/m( 2)). Sequence analysis of p53 in the mutants revealed that the types o f mutations induced mere similar to those obtained in previous studies of UV mutagenesis in other model systems, and the types and positions of mutations were also similar to those found in human skin tumors, T his experimental system will be useful in further evaluation of the im portance of environmental agents as risk factors for cancer.