Pu Yeong-Shiau, Jan Kun-Yan, Wang Tsing-Cheng, Wang Alexander S S, Gurr Jia-Ran
Department of Urology, National Taiwan University College of Medicine, Taipei 10002, Taiwan, ROC.
Toxicol Sci. 2007 Feb;95(2):376-82. doi: 10.1093/toxsci/kfl166. Epub 2006 Nov 13.
Since arsenite is known to induce oxidative DNA damage in human cells, we asked if it induces other types of DNA damage and how the DNA damage is repaired. Treatment of human promyelocytic leukemia NB4 cells with 0.5muM As(2)O(3) for 30 min induced no DNA breaks, as analyzed by a standard comet assay. However, breaks were detected if these cells were then digested with endonuclease III (EnIII), formamidopyrimidine-DNA glycosylase (Fpg), or a nuclear extract (NE) of NB4 cells. Using either H(2)O(2)-Fe-treated nuclei or As(2)O(3)-treated cells, digestion with either NE or EnIII + Fpg generated the same amount of breaks, and subsequent treatment with EnIII + Fpg resulted in no increase in breaks in NE-digested cells and vice versa. The human cell lines, defective in nucleotide excision protein, such as xeroderma pigmentosum (XP) A, XPD, and XPG, excised Ultraviolet C-induced adducts less rapidly than normal fibroblasts, but excised As(2)O(3) adducts at the same rate as the normal cells. Immunodepletion of the NE with antibody against 8-oxoguanine DNA glycosylase (OGG1) or MutY homolog (MYH) decreased the incision of As(2)O(3)-induced adducts, while antibodies against XPA, XPB, XPD, XPF, or XPG, did not. These results suggest that As(2)O(3) induces the formation of only oxidative DNA adducts and that OGG1 and MYH are involved in this incision process.
由于已知亚砷酸盐会在人类细胞中诱导氧化性DNA损伤，我们探究了它是否会诱导其他类型的DNA损伤以及DNA损伤是如何修复的。用0.5μM三氧化二砷（As₂O₃）处理人类早幼粒细胞白血病NB4细胞30分钟，通过标准彗星试验分析发现未诱导出DNA断裂。然而，如果随后用核酸内切酶III（EnIII）、甲酰胺嘧啶-DNA糖基化酶（Fpg）或NB4细胞的核提取物（NE）对这些细胞进行消化，则可检测到断裂。使用经H₂O₂-铁处理的细胞核或经As₂O₃处理的细胞，用NE或EnIII + Fpg消化产生的断裂量相同，随后用EnIII + Fpg处理不会导致NE消化的细胞中断裂增加，反之亦然。在核苷酸切除蛋白方面存在缺陷的人类细胞系，如着色性干皮病（XP）A、XPD和XPG，切除紫外线C诱导的加合物的速度比正常成纤维细胞慢，但切除As₂O₃加合物的速度与正常细胞相同。用抗8-氧代鸟嘌呤DNA糖基化酶（OGG1）或MutY同源物（MYH）的抗体对NE进行免疫去除会减少As₂O₃诱导的加合物的切口，而抗XPA、XPB、XPD、XPF或XPG的抗体则不会。这些结果表明，As₂O₃仅诱导氧化性DNA加合物的形成，并且OGG1和MYH参与了这个切口过程。
