Biochemical Evaluation of Genotoxic Biomarkers for 2-Deoxyribonolactone-Mediated Cross-Link Formation with Histones

Numerous environmental carcinogens involve radical formation interacting with DNA to produce 2-deoxyribonolactone (dL), a major type of oxidized abasic site, implicated in DNA strand breaks, mutagenesis, and formation of covalent DNA–protein cross-links (DPC). Studies showed major dL-specific DPC occurred due to reactions with DNA polymerase β (Polβ) dependent on native conformation, while other DPC formed involved nonenzymatic reactions of DNA binding proteins with dL lesions. Polβ appeared to play a major role in alleviating the cytotoxic effects of neocarzinostatin, which was used as a dL-producing agent. When a duplex DNA containing a dL at a site-specific position was incubated with purified histones, DPC were formed between dL and each histone protein, including H1, H2A, H2B, H3, and H4. Comparative kinetic analysis of DPC formation with histones and Polβ revealed two distinct mechanisms of dL-mediated DPC formation. The rate of DPC formation with Polβ was approximately two orders of magnitude highe...