Establishment of Cell Strains Deficient in Genes Related to Mutation Induction, and Analysis of Mutation Mechanisms Using the Cell Strains.

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Recently, several kinds of DNA polymerases have been found in Eschericnia coil and mammalian cells. The first purpose of this study is to elucidate roles of these DNA polymerases on mutation induction and DNA damage avoidance. The second purpose of this study is to investigate the types of base changes arisen from specific base damage by these DNA polymerases.We cloned DNA polymerase ζ(Rev3) cDNA from chicken DT40 cells, and established hprpt (+/-) heterozygous cell, lines by the somatic recombination method to utilize mutation assay. We also established a DT40 cell line deficient in xeroderma pigmentosum A (XPA) gene, and comfirmed UV hypersensitivity of the cell line.We constructed the plasmid containing one 3-nitrobenzanthrone (NBA) adduct on a guanine base of the plasmid and rendered the plasmid to replicate in E. coil. We found that an adenine is inserted at the opposite site of the guanine having a NBA adduct. We found that bydroquinone, a metabolite of benzene, produces reactive oxygene species in the presence of NADH and copper ions, and causes G : C →A : T transition mutations in mammalian cells.These results clarified a part of the pathway leading to base changes from DNA damage, and provided the advance toward the clarification of complete mutation mechanisms.