Departamento de Biofísica e Biometria, Instituto de Biologia Roberto Alcantara Gomes, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
Redox Rep. 2012;17(3):95-100. doi: 10.1179/1351000212Y.0000000006.
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.
我们之前已经证明活性氧（ROS）可能参与了大肠杆菌细胞中紫外线 C（UVC）诱导的 DNA 损伤。在本研究中，我们评估了 GO 系统蛋白在修复 8-氧代-7,8-二氢-2'-脱氧鸟苷（8-氧代 G，GO）损伤中的作用，该损伤是由 ROS 诱导的氧化损伤引起的。我们首先发现，产生铁积累的突变菌株Δfur 和用铁螯合剂 2,2'-联吡啶处理的细胞对 UVC 诱导的致死性的抗性与野生菌株一样。8-氧代 G 可以被单线态氧（(1)O(2)）介导。Fpg 蛋白在与 C（胞嘧啶）连接时修复这种损伤，而 MutY 蛋白在与 A（腺嘌呤）连接时修复 8-氧代 G。生存分析表明，Fpg 蛋白而非 MutY 蛋白对 UVC 诱导的致死性很重要，并且与 UvrA 蛋白相互作用，UvrA 蛋白是参与 UVC 修复的核苷酸切除修复（NER）蛋白。来自“8-氧代 G 修复”GO 系统的突变菌株中的 GC-TA 回复实验表明，Fpg 突变体而非 MutY 菌株中的 UVC 诱导突变。转化实验表明，Fpg 蛋白在 UVC 修复中很重要。这些结果表明，UVC 还可能导致间接的 ROS 介导的 DNA 损伤，并且 Fpg 蛋白在修复这种间接损伤中起主要作用。
