MUTAGENIC SPECIFICITY OF MODEL ESTROGEN - DNA-ADDUCTS IN MAMMALIAN-CELLS

Site-specifically modified oligodeoxynucleotides were used to explore the mutagenic properties of the model estrogen-DNA adducts ,3,5(10)-tr ien-6(alpha,beta)-yl]-2'-deoxyguanosine (dG-N-2-3MeE) and ,3,5(10)-tri en-6(alpha,beta)-yl]-2'-deoxyadenosine (dA-N-6-3MeE) in simian kidney (COS-7) cells. Oligodeoxynucleotides ((TCCTCCTCXCCTCTC)-T-5'; X = dG, dA, dG-N(2-)3MeE, or dA-N-6-3MeE) containing an unmodified or model es trogen lesion were inserted into single-stranded (ss) phagemid vectors . These ss vectors were transfected into COS-7 cells. The progeny plas mid obtained were used to transform Escherichia coli DH10B. The transf ormants were analyzed by oligodeoxynucleotide hybridization and sequen cing to determine the mutation frequency and spectrum. Preferential in corporation of dCMP, the correct base, was observed opposite the dG-N2 -3MeE lesion. Targeted mutations showing G --> T transversions were de tected, along with a small number of G --> C transversions. When a dA- N-6-3MeE-modified oligodeoxynucleotide was used, preferential incorpor ation of dTMP, the correct base, was also observed. Targeted mutations representing A --> T transversions were detected, accompanied by a sm all amount of A --> G transitions. The frequency of mutation observed opposite dA-N-6-3MeE (17.5%) was 2.3 times higher than that observed o pposite dG-N-2-3MeE (7.5%). These results indicate that estrogen DNA a dducts have mutagenic potential in mammalian cells.