Lack of Direct Involvement of 8‐Hydroxy‐2′‐deoxyguanosine in Hypoxanthine‐guanine Phosphoribosyltransferase Mutagenesis in V79 Cells Treated with N,N'‐Bis(2‐hydroxyperoxy‐2‐methoxyethyl)‐l,4,5,8‐naphthalenetetracarboxylic‐diimide (NP‐III) or Riboflavin

The object of this study is to investigate the relationship between a typical product of oxidative DNA damage, 8‐hydroxy‐2′‐deoxyguanosine (8OHdG), and mutagenesis in V79 cells through a molecular analysis of hypoxanthine‐guanine phosphoribosyltransferase (hprt) gene mutants. We performed a direct sequencing analysis of the cDNA of mutants obtained after treatment with N,N'‐bis(2‐hydroxyperoxy‐2‐methoxyethyl)‐l,4,5,8‐naphthalenetetracarboxylic‐diimide (NP‐III) or riboflavin, each of which induces the formation of 8OHdG in cellular DNA upon UVA irradiation. The frequency of mutation after both treatments was no more than 2 to 5 times the control value. A considerable number of the mutants could not be amplified by RT‐PCR, and this was also the case for the control mutants. Among the mutants analyzed, deletions and a TA→Ã transversion occurred predominantly. The reasons for the weak association of induction of 8OHdG with frequency of mutation and the possible mechanism of oxidative‐stress‐derived mutagenesis are discussed.