COMPARISON OF THE SITES OF REACTION OF 3 POLYCYCLIC AROMATIC-HYDROCARBONS IN THE SUPF GENE

The distribution of hydrocarbon-DNA adducts through the supF gene in p lasmid pS189 was examined using the polymerase arrest assay. For three hydrocarbon dihydrodiol epoxides, derived from 5-methylchrysene, 7-me thylbenz[a]anthracene, and benzo[a]pyrene, that exhibit a preference f or reaction with guanine residues in DNA, polymerase arrest spectra we re similar but not identical. For each agent, guanines in different se quence contexts exhibited varying reactivities and each specific guani ne did not necessarily respond to each agent in the same fashion. Thus , sequence context together with the individual dihydrodiol epoxide's chemical and physical properties all play a role in determining sites and extents of reaction within a specific gene. The polymerase arrest data were not predictive of the known sites of mutation hotspots for t hese dihydrodiol epoxides in the supF gene indicating that further act ion upon the adducted DNA by repair systems is probably necessary to d etermine which specific chemical adducts will ultimately give rise to mutation.