The oxidized deoxynucleoside triphosphate pool is a significant contributor to genetic instability in mismatch repair-deficient cells
The oxidized deoxynucleoside triphosphate pool is a significant contributor to genetic instability in mismatch repair-deficient cells
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DOI：
10.1128/mcb.24.1.465-474.2004
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发表时间：
2004-01-01
影响因子：
5.3
通讯作者：
Bignami, M
中科院分区：
文献类型：
--
作者：
Russo, MT;Blasi, MF;Bignami, M
氧化是DNA损伤的一种常见形式，嘌呤尤其易受其影响。我们之前报道过氧化的dGTP是哺乳动物细胞中DNA 8-氧化gmp的潜在重要来源，并且合并的病变可以通过DNA错配修复（MMR）去除。MMR缺陷与突变表型和广泛的微卫星不稳定性（MSI）有关。在这里，我们确定氧化脱氧核苷三磷酸（dNTPs）作为一个重要的辅助因素在这种遗传不稳定性。mmr缺陷的msh2（-/-）小鼠胚胎成纤维细胞的高自发性hprt突变率可以通过表达hMTH1蛋白来降低，hMTH1蛋白可以降解氧化嘌呤dNTPs。高水平的hMTH1消除了他们的突变表型，并使hprt突变率恢复正常。hprt突变体的分子分析表明，hMTH1的存在降低了所有类型突变的发生率，包括帧移位，并且还涉及在突变表型中掺入2-oxodAMP。在hmsh6缺失的DLD-1人结直肠癌细胞中，过表达hMTH1可显著降低自发性突变率，降低MSI。它还降低了hmlh1缺陷DU145人前列腺癌细胞系中-G和-A移框的发生率。我们的研究结果表明，来自dNTP池的氧化嘌呤的结合可能对mmr缺陷的人类肿瘤的极端遗传不稳定性起重要作用。
Oxidation is a common form of DNA damage to which purines are particularly susceptible. We previously reported that oxidized dGTP is potentially an important source of DNA 8-oxodGMP in mammalian cells and that the incorporated lesions are removed by DNA mismatch repair (MMR). MMR deficiency is associated with a mutator phenotype and widespread microsatellite instability (MSI). Here, we identify oxidized deoxynucleoside triphosphates (dNTPs) as an important cofactor in this genetic instability. The high spontaneous hprt mutation rate of MMR-defective msh2(-/-) mouse embryonic fibroblasts was attenuated by expression of the hMTH1 protein, which degrades oxidized purine dNTPs. A high level of hMTH1 abolished their mutator phenotype and restored the hprt mutation rate to normal. Molecular analysis of hprt mutants showed that the presence of hMTH1 reduced the incidence of mutations in all classes, including frameshifts, and also implicated incorporated 2-oxodAMP in the mutator phenotype. In hMSH6-deficient DLD-1 human colorectal carcinoma cells, overexpression of hMTH1 markedly attenuated the spontaneous mutation rate and reduced MSI. It also reduced the incidence of -G and -A frameshifts in the hMLH1-defective DU145 human prostatic cancer cell line. Our findings indicate that incorporation of oxidized purines from the dNTP pool may contribute significantly to the extreme genetic instability of MMR-defective human tumors.