Oxidative DNA damage and mutations induced by a polar photosensitizer, Ro19-8022

The oxidative DNA damage induced by the polar photosensitizer Ro19-8022 in the presence of light was studied and correlated with the associated mutage nicity. Both in isolated DNA and AS52 Chinese hamster ovary cells, photoexc ited Ro19-8022 gave rise to a DNA damage profile that was similar to that c aused by singlet oxygen: base modifications sensitive to the repair endonuc lease Fpg protein, which according to high-performance liquid chromatograph y (HPLC) analysis were predominantly 8-hydroxyguanine (g-oxoG) residues, we re generated in much higher yield than single-strand breaks, sites of base loss (AP sites) and oxidative pyrimidine modifications sensitive to endonuc lease III. Fifty percent of the Fpg-sensitive modifications were repaired w ithin 2 h. Under conditions that induced 10 Fpg-sensitive modifications per 10(6) bp (six 8-oxoG residues per 10(6) bp), approximately 60 mutations pe r 106 cells were induced in the gpt locus of the AS52 cells. A rather simil ar mutation frequency was observed when a plasmid carrying the gpt gene was exposed to Ro19-8022 plus light under cell-free conditions and subsequentl y replicated in bacteria. Sequence analysis revealed that GC --> TA and GC --> CG transversions accounted for 90% of the base substitutions. A signifi cant generation of micronuclei was detectable in AS52 cells exposed to the photosensitizer plus light as well. (C) 1999 Elsevier Science B.V. All righ ts reserved.