Reactive oxygen species (ROS) are formed exogenously and endogenously and attack DNA showing a preference among bases for reaction with 2’-deoxyguanosine (dG) sites. In the present work, dG was oxidized by free HO• that was generated via the iron-Fenton reaction or by X-ray radiolysis of water. The primary oxidized lesions observed include the 2’-deoxynucleosides of 8-oxo-7,8-dihydroguanosine (dOG), spiroiminodihydantoin (dSp), guanidinohydantoin (dGh), oxazolone (dZ), 5-carboxamido-5-formamido-2-iminohydantoin (d2Ih), and 5’,8-cycloguanosine (cyclo-dG), as well as the free base guanine. Under aerobic conditions and in presence of reductant (ascorbate (ASC) or N-acetylcysteine (NAC)), the product d2Ih was the major lesion formed. O2- and reductant-dependence studies have been conducted to investigate their role in formation of oxidation products. Mechanisms are proposed to support the observation that d2Ih was the major oxidation product detected under aerobic conditions in the presence of reductant in all contexts studied. A synthetic template with d2Ih was subjected to single-nucleotide insertion and primer extension experiments using different DNA polymerases. dGTP and dATP were found to be inserted opposite the d2Ih lesion. Full extension past the d2Ih lesion was significantly reduced compared to the native G. These results demonstrate that the presence of d2Ih will be misread during DNA synthesis, and lead to G to T and G to C transversion mutations.

2-Iminohydantoin, a mutagenic lesion, is a major oxidation product of 2’-deoxyguanosine with hydroxyl radical

249th National Meeting (2015)

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