The assay is based on Ogg1 glycosylase activity that recognizes and removes the mutated base (8-oxo-G). The substrate is a 23 oligonucleotide containing 8-oxo-dG at its 11th base, labeled with 32P at its 5′ end, and annealed to its complementary strand (containing dC at the opposite base position to the 8-oxo-dG). Upon cleavage of the substrate by the Ogg1 enzyme, the oligonucleotide strands are run on a denaturing gel and a 10 base fragment (labeled cleavage product) is revealed in addition to the original 23 base oligonucleotide band. The detection is performed by autoradiography.
Ogg1, a DNA repair protein, is involved in the repair of the major product of DNA oxidation, the miscoding base 8-oxoguanine (8-oxo-G). Polymorphism in the human OGG1 gene is associated with the risk of various cancers such as lung and prostate cancer.