Host: The Japan Radiation Research Society, Chairman of the 52nd Annual Meeting, Toshiteru Okubo (Radiation Effects Research Foundation)
In cells of aerobic organisms, reactive oxygen species (ROS) are continually generated during respiration. ROS are also produced by exposure to ionizing radiation and various chemical oxidizing agents. ROS induce various types of oxidative damage in DNA. Oxidative DNA damage occurs directly in DNA and in dNTPs in the nucleotide pool. Oxidized dNTPs such as 8-oxo-dGTP or 2-OH-dATP could be incorporated into DNA during replication, which could result in mutagenic consequences. Therefore, many organisms have enzymes for eliminating the abnormal dNTPs in the nucleotide pool as well as repair enzymes for damage in DNA. E. coli MutT and human MTH1 can hydrolyze 8-oxo-dGTP, and human MTH1 also hydrolyzes 2-OH-dATP. However, whether there is homolog of these enzymes in C. elegans, a multicellular eukaryote frequently used as a model for the study of development and aging, has remained uncertain. To clarify the mechanism for eliminating oxidized dNTPs and its critical roles in maintaining the genome stability in C. elegans, we selected three genes as players in sanitization of the nucleotide pool by homology search. Proteins encoded by the three genes were purified and their enzymatic activity was examined by using HPLC. None of the three enzymes could hydrolyze 8-oxo-dGTP or 2-OH-dATP, but one hydrolyzes 8-oxo-dGDP. The finding provides one possible mechanism of how the dNTP pool is sanitized in C. elegans. For this enzyme, divalent cation dependence were experimentally determined. We will show these data.
