DNA Structure-Dependent Enrichment of Oxidative Lesions

Oxidative DNA lesions such as 8-oxo-7,8-dihydroguanine (8-oxoG) and abasic (AP) sites contribute to mutagenesis and genetic instability. H-DNA, a naturally occurring intramolecular triplex structure, promotes genetic instability and is susceptible to oxidative damage. Here, we examined how oxidative lesions distribute within an H-DNA-forming sequence. Although oxidative stress increased oxidized purines overall, no template-dependent differences were detected at a distal B-DNA locus. In contrast, AP sites and FPG-sensitive lesions were enriched within the H-DNA region relative to the B-DNA control, even under basal conditions. These findings indicate that H-DNA topology enhances local susceptibility to oxidative damage and shapes the spatial distribution of oxidative DNA lesions that can contribute to mutagenesis.