Mutation in the glucose-6-phosphate dehydrogenase gene leads to inactivation of Ku DNA end binding during oxidative stress
Mutation in the glucose-6-phosphate dehydrogenase gene leads to inactivation of Ku DNA end binding during oxidative stress
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DOI：
10.1074/jbc.m111366200
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发表时间：
2002-03-22
影响因子：
4.8
通讯作者：
Koch, CJ
中科院分区：
文献类型：
--
作者：
Ayene, IS;Stamato, TD;Koch, CJ
葡萄糖-6-磷酸脱氢酶（G6 PD）是氧化戊糖磷酸循环的限速酶，调节真核细胞中NADPH/NADP（+）的比例。G6 PD缺乏症是人类最常见的突变之一，已知会导致全球数亿人的健康问题。虽然已知G6 PD功能降低可导致对氧化应激的易感性增加，但这种应激的分子靶点尚不清楚。使用中国仓鼠卵巢G6 PD无效突变体，我们以前证明，暴露于巯基特异性氧化剂，羟乙基二硫化物，引起辐射敏感性增强，无法修复DNA双链断裂。我们现在证明了这些观察的分子机制：直接抑制DNA末端结合活性的Ku异源二聚体，DNA修复蛋白，其半胱氨酸残基的氧化。Ku DNA末端结合的抑制被发现是可逆的，通过处理的核提取物与二硫苏糖醇，表明在Ku中的半胱氨酸残基的还原的稳态调节是G6 PD和氧化戊糖循环的关键功能。总之，我们发现了一个新的DNA损伤修复层，即修复蛋白本身的功能维护。鉴于辜振甫的角色数量迅速增加，这些结果可能会产生广泛的影响。
Glucose-6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme of the oxidative pentose phosphate cycle, regulates the NADPH/NADP(+) ratio in eukaryotic cells. G6PD deficiency is one of the most common mutations in humans and is known to cause health problems for hundreds of millions worldwide. Although it is known that decreased G6PD functionality can result in increased susceptibility to oxidative stress, the molecular targets of this stress are not known. Using a Chinese hamster ovary G6PD-null mutant, we previously demonstrated that exposure to a thiol-specific oxidant, hydroxyethyldisulfide, caused enhanced radiation sensitivity and an inability to repair DNA double strand breaks. We now demonstrate a molecular mechanism for these observations: the direct inhibition of DNA end binding activity of the Ku heterodimer, a DNA repair protein, by oxidation of its cysteine residues. Inhibition of Ku DNA end binding was found to be reversible by treatment of the nuclear extract with dithiothreitol, suggesting that the homeostatic regulation of reduced cysteine residues in Ku is a critical function of G6PD and the oxidative pentose cycle. In summary, we have discovered a new layer of DNA damage repair, that of the functional maintenance of repair proteins themselves. In view of the rapidly escalating number of roles ascribed to Ku, these results may have widespread ramifications.