Glyoxal, a major product of DNA oxidation, induces mutations at G:C sites on a shuttle vector plasmid replicated in mammalian cells

Glyoxal is a major product of DNA oxidation in which Fenton-type oxygen free radical-forming systems are involved, To determine the mutation spectrum of glyoxal in mammalian cells and to compare the spectrum with those observed in other experimental systems, we analyzed mutations in a bacterial suppressor tRNA gene (supF) in the shuttle vector plasmid pMY189. We treated pMY189 with glyoxal and immediately transfected it into simian COS-7 cells, The cytotoxicity and mutation frequency increased according to the dose of glyoxal, The majority of glyoxal-induced mutations (48%) were single-base substitutions. Eighty three percent of the single-base substitutions occurred at G:C base pairs, Among them, G:C-->T:A transversions were predominant, followed by G:C-->C:G transversions and G:C-->A:T transitions, A:T-->T:A transversions were also observed, Mutational hotspots within the supF gene were detected,:These results suggest that glyoxal may play an important role in mutagenesis induced by oxygen free radicals.