Abstract
DNA pyrimidines are continuously oxidized in physiological condition. The productive damaged pyrimidines are thought to be repaired majorly by single nucleotide-base excision repair pathway. The mammalian homologs of endonuclease III and endonuclease VIII, NTH1 and NEIL1, are well known as oxidized pyrimidine-DNA glycosylases, and thought to have a major contribution to remove oxidized pyrimidines in mammals. We found an unidentified monofunctional thymine glycol (TG)-DNA glycosylase (TGG) activity in nuclei of mouse organs. Based on studies of comparison of the activity levels between organs and species, we concluded that higher level of the TGG activity is observed in more proliferative cells and in organisms which have shorter life-span. In this study, we purified the TGG activity protein from mouse cultured cell, L1210, which is derived from leukemia cell. L1210 has advantages; mouse genome database is fulfilled and the cell has high proliferative activity. We prepared whole cell extract, and performed hydroxyapatite column, ion-exchange column and gel-filtration column chromatography. The calculated molecular size of the TGG activity protein from L1210 cells was less than 25.7 kDa.
