Institut Jacques Monod, CNRS-Université Paris Diderot, Sorbonne Paris Cité, 15 rue Hélène Brion, 75205 Paris cedex 13, France.
Hum Mol Genet. 2012 Sep 15;21(18):4060-72. doi: 10.1093/hmg/dds230. Epub 2012 Jun 16.
Frataxin deficiency results in mitochondrial dysfunction and oxidative stress and it is the cause of the hereditary neurodegenerative disease Friedreich ataxia (FA). Here, we present evidence that one of the pleiotropic effects of oxidative stress in frataxin-deficient yeast cells (Δyfh1 mutant) is damage to nuclear DNA and that repair requires the Apn1 AP-endonuclease of the base excision repair pathway. Major phenotypes of Δyfh1 cells are respiratory deficit, disturbed iron homeostasis and sensitivity to oxidants. These phenotypes are weak or absent under anaerobiosis. We show here that exposure of anaerobically grown Δyfh1 cells to oxygen leads to down-regulation of antioxidant defenses, increase in reactive oxygen species, delay in G1- and S-phases of the cell cycle and damage to mitochondrial and nuclear DNA. Nuclear DNA lesions in Δyfh1 cells are primarily caused by oxidized bases and single-strand breaks that can be detected 15-30 min after oxygen exposition. The Apn1 enzyme is essential for the repair of the DNA lesions in Δyfh1 cells. Compared with Δyfh1, the double Δyfh1Δapn1 mutant shows growth impairment, increased mutagenesis and extreme sensitivity to H(2)O(2). On the contrary, overexpression of the APN1 gene in Δyfh1 cells decreases spontaneous and induced mutagenesis. Our results show that frataxin deficiency in yeast cells leads to increased DNA base oxidation and requirement of Apn1 for repair, suggesting that DNA damage and repair could be important features in FA disease progression.
铁蛋白缺乏导致线粒体功能障碍和氧化应激，是遗传性神经退行性疾病弗里德里希共济失调（FA）的原因。在这里，我们提供的证据表明，氧化应激在铁蛋白缺乏酵母细胞（Δyfh1 突变体）中的一个多效性效应是核 DNA 的损伤，并且修复需要碱基切除修复途径的 Apn1 AP-内切酶。Δyfh1 细胞的主要表型是呼吸缺陷、铁稳态紊乱和对氧化剂的敏感性。这些表型在厌氧条件下较弱或不存在。我们在这里表明，暴露于氧气下的厌氧生长的Δyfh1 细胞导致抗氧化防御的下调、活性氧的增加、细胞周期的 G1 和 S 期的延迟以及线粒体和核 DNA 的损伤。Δyfh1 细胞中的核 DNA 损伤主要是由氧化碱基和单链断裂引起的，这些损伤可以在暴露于氧气 15-30 分钟后检测到。Apn1 酶是修复Δyfh1 细胞中 DNA 损伤所必需的。与Δyfh1 相比，双Δyfh1Δapn1 突变体显示出生长受损、增加的突变和对 H（2）O（2）的极端敏感性。相反，在Δyfh1 细胞中过表达 APN1 基因可降低自发和诱导的突变。我们的研究结果表明，酵母细胞中铁蛋白缺乏导致 DNA 碱基氧化增加和 Apn1 修复的需求，提示 DNA 损伤和修复可能是 FA 疾病进展的重要特征。
