Synthesis and Characterization of Chemically Stable N7-dG Estrone and Catechol Adducts

Endogenous estrogens are implicated in carcinogenesis through both estrogen receptor-mediated cell proliferation and the direct genotoxicity of reactive metabolites. Oxidative metabolism of estrogens produces catechol estrogens that are further converted to electrophilic ortho-quinones capable of alkylating DNA. The prevailing model of mutagenesis proposes that these N3Ade and N7Gua adducts depurinate to form abasic sites that induce mutations initiating hormone-related cancers. However, the mutation spectrum observed in experimental data is inconsistent with this mechanism, and synthetic studies of estrogen-DNA adducts have relied on acidic conditions that artificially promote depurination, leaving stable N7-dG lesions poorly understood. To address this, we synthesized stable N7-dG catechol and estrone adducts using 2'-fluorinated deoxyguanosine, a modification that inhibits N-glycosidic bond cleavage. ROESY 2D NMR spectroscopy revealed through-space correlations consistent with a preferred anti-conformation in solution, supported by molecular modeling. Structural analysis suggests that these cationic aryl adducts likely preserve the Watson-Crick base pairing edge but may promote tautomerization capable of altering base pairing and generating G-to-A mutations. These findings provide the first synthesized stable models of N7-dG estrogen adducts and may support an alternative mechanism of estrogen-induced mutagenesis independent of depurination, enabling future biochemical investigations of related DNA repair and mutagenesis.