Mutagenic potential of guanine N-2 adducts of butadiene mono- and diolepoxide

To explore the role of guanine N-2 adducts of st;stereoisomeric bu;diene me tabolites in butadiene-induced mutagenesis, Il-mer deoxyoligonucleotides we re prepared containing adducts of (R)- and (S)-monoepoxide and (RP)- and (S ,S)-diolepoxide. These adducted oligonucleotides were utilized in both in v ivo and in vitro experiments designed to examine the mutagenic potency of e ach and their replication by Escherichia coli polymerases. Each of the four adducted deoxyoligonucleotides was ligated into a single-stranded M13mp7L2 vector and transfected into E. coli. The-resulting plaques were screened f or misincorporation at position 2 of the N-ras 12 codon. Although the mutag enic frequencies were low, different relative mutagenicities of the various stereoisomers were discernible. In addition, the biological effects of eac h adduct on the three major E. coli polymerases were determined via primer extension assays. The adducted 11-mers were ligated into a 60-mer linear DN A molecule to provide a sufficiently long template for primer elongation. A ll four guanine adducts were determined to be blocking to each of the three polymerases via primer extension assays.