Mutagenic specificity of (acetylamino)fluorene-derived DNA adducts in mammalian cells.
Site-specifically modified oligodeoxynucleotides were used to explore the mutagenic potential of dG-AAF and dG-AF adducts in mammalian cells. The miscoding properties of these arylamine adducts were established by analyzing fully extended products of primer extension reactions catalyzed by mammalian DNA polymerases alpha, beta, and delta. On DNA templates containing dG-AAF, pol alpha generated two-base deletions and promoted incorporation of small amounts of dCMP, dAMP, and dTMP opposite the lesion. Reactions with pol beta were associated exclusively with two-base deletions. Primer extension catalyzed by pol delta was strongly blocked by the adduct. On DNA templates containing dG-AF, all three DNA polymerases generated full-length products, preferentially incorporating dCMP opposite the lesion. A single-stranded shuttle vector containing 5'TCCTCCTCXCCTCTC (X = dG-AAF, dG-AF, or dG) was used to establish the frequency and specificity of dG-AAF- and dG-AF-induced mutations in simian kidney (COS-7) cells. Vectors containing a single dG-AAF or dG-AF adduct promote significant incorporation of dAMP and lesser amounts of dTMP opposite the lesion. dG-AAF also promoted some incorporation of dGMP and a two-base deletion. dG-AAF was 3.8 times more mutagenic than dG-AF (11% vs 2.9%) in COS cells. We conclude from this study that dG-AAF and dG-AF produce G --> T transversions and, to a much lesser degree, G --> A transitions in mammalian cells.