Cytotoxic and Mutagenic Properties of C1′ and C3′-Epimeric Lesions of 2′-Deoxyribonucleosides in Human Cells

Genomic integrity is constantly challenged by exposure to environmental and endogenous genotoxic agents. Reactive oxygen species (ROS) represent one of the most common types of DNA damaging agents. While ROS mainly induce single-nucleobase lesions, epimeric 2-deoxyribose lesions can also be induced upon hydrogen atom abstraction from the C1′, C3′, or C4′ carbon and the subsequent incorrect chemical repair of the resulting carbon-centered radicals. Herein, we investigated the replicative bypass of the C1′- and C3′-epimeric lesions of the four 2′-deoxynucleosides in HEK293T human embryonic kidney epithelial cells. Our results revealed distinct bypass efficiencies and mutagenic properties of these two types of epimeric lesions. Replicative bypasses of all C1′-epimeric lesions except α-dA are mutagenic in HEK293T cells, and their mutagenic properties are further modulated by translesion synthesis (TLS) DNA polymerases. By contrast, none of the four C3′-epimeric lesions are mutagenic, and the replicative bypas...