The activity of the DNA repair enzyme hOGG1 can be directly modulated by ubiquinol

Abstract

The DNA of human cells suffers about 1.000-100.000 oxidative lesions per day. One of the most common defects in this category is represented by 7,8-dihydro-8-oxoguanine. There are numerous exogenous effects on DNA that induce the intracellular generation of 7, 8-dihydro-8-oxoguanine. Therefore, a quantitatively sufficient repair of all occurring oxidative damaged guanine bases is often only partially feasible, especially in advanced age. Inadequate removal of these damages can subsequently lead to mutations and thus to serious diseases. All these aspects represent a dangerous situation for an organism. However, it is suspected that the amount of the 8-oxoguanine DNA glycosylase can be actively regulated on the level of gene expression by the redox-active properties of ubiquinol and thus its protein expression can be controlled. Using an real-time base excision repair assay including a melting curve analysis, the activity of the human 8-oxoguanine DNA glycosylase 1 was measured under the influence of ubiquinol. It was possible to observe a concentration-dependent increase in the activity of the 8-oxoguanine DNA glycosylase 1 under the influence of ubiquinol for the first time, both on purified and commercially acquired enzyme as well as on enzyme isolated from mitochondria of human fibroblasts. An increase in activity of this enzyme based on a change in cellular redox state caused by ubiquinol could not be confirmed. In addition, an increased gene expression of 8-oxoguanine-DNA glycosylase 1 under ubiquinol could not be observed. However, there was a change in bifunctionality in favor of an increased N-glycosylase activity and a direct interaction between ubiquinol and 8-oxoguanine DNA glycosylase 1. We suggest that ubiquinol contributes to the dissolution of a human 8-oxoguanine DNA glycosylase 1 end-product complex that forms after cutting into the sugar-phosphate backbone of the DNA with the resulting unsaturated 3'-phospho-α, β-aldehyde end and thereby inhibits further enzymatic steps.

Keywords: 8-Oxoguanine; DNA repair; Enzyme activity; Mitochondria; Ubiquinol; hOGG1.