Ubiquitous Presence in Mammalian Cells of Enzymatic Activity Specifically Cleaving 8‐Hydroxyguanine‐containing DNA

Here we report the finding of enzymatic activity that specifically cleaves DNA containing 8‐hydroxyguanine (oh(8)Gua) residues in various mammalian cells. To detect this activity, we used a synthetic double‐stranded DNA containing a single oh(8)Gua at a defined position as the substrate, and analyzed the products of enzymatic digestion by polyacrylamide gel electrophoresis. Two cleavage sites near the oh(8)Gua residue were detected with partially purified fractions from cow brain and rat liver, and also with preparations from all mammalian tissues examined. These results suggest that enzymatic activity for the removal of oh(8)Gua from DNA is widely distributed in mammalian cells.