Characterization of hOGG1 Promoter Structure, Expression During Cell Cycle and Overexpression in Mammalian Cells

Oxygen radicals are produced in all cells either by the normal cellular metabolism or by the exposure to external mutagens. The reactive oxygen species (ROS) generated can induce DNA damage. Among the principal lesions found in DNA due to ROS is an oxidized form of guanine, 8-oxo-7,8-dihydroguanine (8-oxoG). The biological relevance of this lesion has been unveiled by the study of Escherichia colt and Saccharomyces cerevisiae genes involved in the neutralization of the mutagenic effects of 8-oxoG (Cabrera et al., 1988; Nghiem et al., 1988; Radicella et al., 1988; van der Kemp et al., 1996). These genes fpg and mutY for E. colt and OGG1 for yeast, code for DNA glycosylases. Inactivation of a…

Overexpression of Ogg1 in mammalian cells: effects on induced and spontaneous oxidative DNA damage and mutagenesis

Chinese hamster ovary cell lines (AA8 and AS52) were stably transfected to overexpress hOgg1 protein, the human DNA repair glycosylase for 7,8-dihydro-8-oxoguanine (8-oxoG). In the transfectants, the repair rate of 8-oxoG residues induced by either potassium bromate or the photosensitizer [R]-1-[(10-chloro-4-oxo-3-phenyl-4H-benzo[a]quinolizin-1-yl)-carbo nyl ]-2-pyrrolidinemethanolplus light was up to 3-fold more rapid than in the parental cells. However, the improved repair had little effect on the mutagenicity of potassium bromate in the guanine phosphoribosyl transferase (gpt) locus of the OGG1-transfected AS52 cells. The steady-state (background) levels of DNA base modifications sensiti…

Contributions - C: Carcinogenic Factors: Endogenous

Age-related and tissue-specific accumulation of oxidative DNA base damage in 7,8-dihydro-8-oxoguanine-DNA glycosylase (Ogg1) deficient mice.

Mutations that influence the repair of oxidative DNA modifications are expected to increase the steady-state (background) levels of these modifications and thus create a mutator phenotype that predisposes to malignant transformation. We have analysed the steady-state levels and repair kinetics of oxidative DNA modifications in cells of homozygous ogg1(-/-) null mice, which are deficient in Ogg1 protein, a DNA repair glycosylase that removes the miscoding base 8-hydroxyguanine (8-oxoG) from the genome. Oxidative purine modifications including 8-oxoG were quantified by means of an alkaline elution assay in combination with Fpg protein, the bacterial functional analogue of Ogg1 protein. In pri…