Ntg2 of Saccharomyces cerevisiae repairs the oxidation products of 8-hydroxyguanine

In Escherichia coli, endonuclease III (endo III) repairs the oxidation prod ucts of 8-OHGua. However, the corresponding repair enzymes in eukaryotes ha ve not been identified. Here we report that S-hydroxy-guanine (8-OHGua) is highly sensitive to further oxidation. We also show that Ntg2, a functional homolog of endo III in Saccharomyces cerevisiae, is capable of nicking the irradiated duplex DNA containing 8-OHGua. Moreover, Ntg2 formed a stable c omplex with the DNA upon incubation with NaBH4. In contrast, Ntg1, another functional homolog of endo III, showed no such activities. These findings i ndicate that Ntg2 is, at least in part, responsible for repairing the oxida tion products of 8-OHGua in eukaryotic cells. (C) 2001 Academic Press.