Abstract
We previously demonstrated that reactive oxygen species (ROS) could be involved in ultraviolet-C (UVC)-induced DNA damage in Escherichia coli cells. In the present study, we evaluated the involvement of the GO system proteins in the repair of the 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxoG, GO) lesion, which is ROS-induced oxidative damage. We first found that the mutant strain Δfur, which produces an accumulation of iron, and the cells treated with 2,2'-dipyridyl, a iron chelator, were both as resistant to UVC-induced lethality as the wild strain. The 8-oxoG could be mediated by singlet oxygen ((1)O(2)). The Fpg protein repaired this lesion when it was linked to C (cytosine), whereas the MutY protein repaired 8-oxoG when it was linked to A (adenine). The survival assay showed that the Fpg protein, but not the MutY protein, was important to UVC-induced lethality and interacted with the UvrA protein, a nucleotide excision repair (NER) protein involved in UVC repair. The GC-TA reversion assay in the mutant strains from the '8-oxoG-repair' GO system showed that UVC-induced mutagenesis in the fpg mutants, but not in the MutY strain. The transformation assay demonstrated that the Fpg protein is important in UVC repair. These results suggest that UVC could also cause indirect ROS-mediated DNA damage and the Fpg protein plays a predominant role in repairing this indirect damage.