Miscoding potential of N2, 3-ethenoguanine studied in an Escherichia coli DNA-dependent RNA polymerase in vitro system and possible role of this adduct in vinyl chloride-induced mutagenesis

The miscoding potential of N2,3-ethenoguanine (epsilon G), one of the carcinogen vinyl chloride adducts to DNA bases, has been evaluated in an Escherichia coli DNA-dependent RNA polymerase in vitro system. Epsilon G present in poly(C) templates causes incorporation of cytosine (C), uridine (U) and adenosine (A) under competitive and non-competitive conditions, and in the presence of either Mn2+ and Mg2+ cations, indicating that this modified base still retains the coding properties of unmodified G and can also act as A or U. The formation of hydrogen bonded pairs between different tautomeric forms of epsilon G and C, U and A is proposed. The possible role of epsilon G, along with a role of other vinyl chloride adducts in causing of GC----AT transitions, the most frequent mutation induced by a vinyl chloride metabolite, is discussed.