Roles of Lig3 and XRCC1 Genes in Genome Stability

摘要 而线粒体氧化磷酸化产生的三磷酸腺苷为合成 蛋白质、核酸和其他大分子，在这个过程中产生的副产品是活性氧 对环状线粒体基因组构成独特挑战的物种。值得注意的是， 线粒体DNA氧化损伤抑制编码的关键电子传递蛋白的转录 通过线粒体基因组扰乱电子传递导致活性氧进一步增加 物种。除了线粒体中产生的活性氧物种外，一些环境DNA 与核基因组相比，损伤剂优先引起线粒体基因组的损伤。 有趣的是，虽然被氧化的碱基8-氧鸟嘌呤被修复，但氧化DNA损伤也会导致 线粒体基因组的退化。因为每个线粒体基因组都有多个拷贝 细胞器，有人认为通过降解去除受损的基因组有助于防止 突变。对于氧化损伤，目前尚不清楚是什么损伤(S)引发了基因组退化，以及 这会减少突变。在特定的目标1中，我们将检验MUTYH DNA糖基酶保护 线粒体基因组通过稳定地结合到带有8-oxoG：腺嘌呤错对或 8-oxoG：基础部位修复中间体，并使用独特的工具和试剂针对它们进行降解 由PI和co-I开发。拟议的研究将阐明参与氧化的机制。 线粒体中的DNA损伤以修复损伤或针对受损的基因组进行降解。 特异性目标2建立在线粒体DNA连接酶，DNA连接酶之间的一种新的相互作用的基础上 IIIA(LigIIIa)和NDUFAB1，它是电子传输链复合体I的一个辅助亚单位，提供 可能解释为什么LigIIIa抑制剂快速诱导线粒体超氧化物的产生。我们 将表征线粒体LigIIIa和复合体I之间的相互作用，以确定LigIIIa是否具有 在复合体I功能中的非典型作用，从而将线粒体DNA代谢与氧化联系起来 磷酸化。癌症和非恶性细胞对抑制引起的功能障碍的反应截然不同 线粒体LigIIIa的癌细胞激活炎性细胞死亡途径，而非恶性 细胞激活有丝分裂和促炎细胞应激途径。在具体目标3中，我们将划定 辐射致线粒体功能障碍的细胞通路及其调控机制 线粒体LigIIIa在癌症和非恶性细胞中的抑制作用。线粒体功能的改变 通常与氧化应激增加有关，已被确定为某些人的致病因素 代谢性和神经退行性疾病，并与炎症、癌症和衰老有关。因此，我们的 拟议的研究将提供关于线粒体如何维持其基因组的基本见解，并建议 如何减轻或利用线粒体功能障碍来改善人类健康。

ABSTRACT While the ATP production by oxidative phosphorylation in mitochondria provides the energy for the synthesis of proteins, nucleic acids and other macromolecules, this process generates as a by-product reactive oxygen species that present a unique challenge for the circular mitochondrial genome. Notably, the accumulation of oxidative DNA damage in mitochondrial DNA inhibits the transcription of key electron transport proteins encoded by the mitochondrial genome disrupting electron transport leading to a further increase in reactive oxygen species. In addition to the reactive oxygen species generated within mitochondria, some environmental DNA damaging agents preferentially cause damage in the mitochondrial genome compared with the nuclear genome. Interestingly, although the oxidized base 8-oxoguanine is repaired, oxidative DNA damage also induces degradation of the mitochondrial genome. Since there are multiple copies of the mitochondrial genome per organelle, it has been suggested that the removal of damaged genomes by degradation serves to prevent mutations. For oxidative DNA damage, it is not known what lesion(s) triggers genome degradation and whether this reduces mutations. In Specific Aim 1, we will test the hypothesis that the MUTYH DNA glycosylase protects the mitochondrial genome from mutation by stably binding to genomes with the 8-oxoG:adenine mispairs or the 8-oxoG:abasic site repair intermediate and targeting them for degradation using unique tools and reagents developed by the PI and co-I. The proposed studies will elucidate the mechanisms that engage with oxidative DNA damage in mitochondria to either repair the damage or target the damaged genome for degradation. Specific Aim 2 builds upon a novel interaction identified between the mitochondrial DNA ligase, DNA ligase IIIa (LigIIIa) , and NDUFAB1, an accessory subunit of complex I of the electron transport chain that provides possible explanation as to why the LigIIIa inhibitor rapidly induces production of mitochondrial superoxide. We will characterize the interaction between mitochondrial LigIIIa and complex I to determine whether LigIIIa has a non-canonical role in complex I function, thereby linking mitochondrial DNA metabolism with oxidative phosphorylation. Cancer and non-malignant cells respond very differently to the dysfunction caused by inhibition of mitochondrial LigIIIa with cancer cells activating an inflammatory cell death pathway whereas non-malignant cells activate mitophagy and pro-inflammatory cell stress pathways. In Specific Aim 3, we will delineate the mechanisms and regulation of the cellular pathways that respond to mitochondrial dysfunction induced by inhibition of mitochondrial LigIIIa in cancer and non-malignant cells. Alterations in mitochondrial function that are usually associated with increased oxidative stress have been identified as the causative factor in certain human metabolic and neurodegenerative diseases and implicated in inflammation, cancer and ageing. Thus, our proposed studies will provide fundamental insights as to how mitochondria maintain their genome and suggest how mitochondrial dysfunction can be mitigated or exploited to improve human health.