Oxidation by DNA charge transport damages conserved sequence block II, a regulatory element in mitochondrial DNA
Oxidation by DNA charge transport damages conserved sequence block II, a regulatory element in mitochondrial DNA
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DOI：
10.1021/bi062024
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发表时间：
2007-03-13
期刊：
影响因子：
2.9
通讯作者：
Barton, Jacqueline K.
中科院分区：
文献类型：
--
作者：
Merino, Edward J.;Barton, Jacqueline K.
线粒体DNA中的氧化损伤位点已经根据DNA介导的电荷转运被确定。我们的目标是了解线粒体DNA中的哪些位点容易发生长距离氧化，以及这种氧化损伤是否与癌变相关。在这里，我们表明，引物延伸反应可用于监测直接氧化损伤真实的线粒体DNA通过光反应与铑嵌入剂。络合物[Rh（phi）（2）bpy]Cl-3（phi = 9，10-菲醌二亚胺）与DNA结合而无序列特异性，并且在光活化后，促进直接在结合位点处的链断裂或促进单电子氧化损伤;将碱基氧化位点与直接链断裂进行比较，揭示了通过DNA介导的电荷传输从远处产生的氧化损伤。值得注意的是，通过电荷转移的碱基氧化与已知的与癌症相关的突变热点在位置263和303周围的核苷酸重叠;后者被称为保守序列块II，对DNA复制至关重要。由于保守序列区II的DNA碱基氧化会削弱受损线粒体基因组的复制能力，因此DNA介导的电荷转运可能为排除受损DNA提供保护机制。
Sites of oxidative damage in mitochondrial DNA have been identified on the basis of DNA-mediated charge transport. Our goal is to understand which sites in mitochondrial DNA are prone to oxidation at long range and whether such oxidative damage correlates with cancerous transformation. Here we show that a primer extension reaction can be used to monitor directly oxidative damage to authentic mitochondrial DNA through photoreactions with a rhodium intercalator. The complex [Rh(phi)(2)bpy]Cl-3 (phi = 9,10-phenanthrenequinone diimine) binds to DNA without sequence specificity and, upon photoactivation, either promotes strand breaks directly at the binding site or promotes one-electron oxidative damage; comparing the sites of base oxidation to direct strand breaks reveals the oxidative damage that arises from a distance through DNA-mediated charge transport. Significantly, base oxidation by charge transport overlaps with known mutational hot spots associated with cancers at nucleotides surrounding positions 263 and 303; the latter is known as conserved sequence block II and is vital to DNA replication. Since DNA base oxidation at conserved sequence block II should weaken the ability of damaged mitochondrial genomes to be replicated, DNA-mediated charge transport may provide a protection mechanism for excluding damaged DNA.