Oxidative DNA Damage And Its Processing

氧化损伤主要通过碱基切除修复（BER）途径从DNA中去除。BER通过四个酶促步骤进行，但现在清楚的是，其他几种蛋白质通过蛋白质-蛋白质相互作用调节BER效率。我们和其他人确定了核心BER酶的几种蛋白质相互作用。氧化性DNA损伤与脑老化、神经变性和神经系统疾病有关。损伤可以由正常的细胞代谢产生，其随着年龄的增长而积累，或者由急性细胞应激条件产生氧化损伤的爆发。脑细胞具有特别高的基础代谢活性水平，并使用不同的氧化损伤修复机制来去除DNA和dNTP库中的氧化损伤。在功能性DNA修复反应的背景下，这种损伤的积累与正常衰老有关，但脑细胞的修复缺陷可能导致神经功能障碍。增殖细胞对BER的需求也与DNA损伤后神经发生中许多BER酶的高水平相关。然而，该途径也是正常神经维持所必需的，因为在一些糖基化酶缺乏的动物中观察到缺血性卒中后较大的梗死体积。此外，在有丝分裂后BER中对DNA聚合酶的需求可能比在增殖细胞中更重要，这是由于复制聚合酶的水平降低。BER反应可能与许多与氧化应激增加相关的神经退行性疾病（包括我们正在研究的阿尔茨海默氏症）的发作和进展特别相关。 遗传和环境因素可能会影响DNA修复能力。为了更深入地了解遗传和环境对DNA修复的分子基础的贡献，我们进行了一项人类双胞胎研究，重点关注一些最丰富类型的DNA损伤（单链断裂）和一些最危险的病变（DNA双链断裂）的后果。DNA损伤信号转导反应（γ-H2 AX信号），内源性损伤的相对量，和DNA链断裂修复能力进行了研究，在外周血单核细胞从198双胞胎（94单卵和104双卵）。在我们的研究中，我们没有检测到DNA链断裂变量的遗传效应。在另一项研究中，我们关注了人外周血单核细胞（PBMC）中DNA损伤反应的潜在年龄相关变化以及修复DNA单链断裂（SSB）和双链断裂（DSB）的能力。在这些病变中，DSB是最不常见的，但对细胞最危险。我们测量了内源性SSB水平，SSB修复能力，-H2 AX反应，DSB修复能力的研究人群组成的216个人从人口为基础的样本，年龄在40-77岁的双胞胎。在此范围内的年龄似乎对SSB参数没有任何影响。然而，-H2 AX反应和DSB修复能力随着年龄的增长而下降，尽管在多个实验中调整批次效应后，这种关联没有达到统计学显著性。分析的任何参数均未观察到性别差异。我们的研究结果表明，在PBMC中，SSB的修复维持到老年，而DSB的反应和修复下降。

Oxidative lesions are removed from DNA primarily via the base excision repair (BER) pathway. BER is carried out through four enzymatic steps, but it is now clear that several other proteins modulate BER efficiency through protein-protein interactions. We and others identified several protein interactions for the core BER enzymes. Oxidative DNA damage is implicated in brain aging, neurodegeneration and neurological diseases. Damage can be created by normal cellular metabolism, which accumulates with age, or by acute cellular stress conditions which create bursts of oxidative damage. Brain cells have a particularly high basal level of metabolic activity and use distinct oxidative damage repair mechanisms to remove oxidative damage from DNA and dNTP pools. Accumulation of this damage in the background of a functional DNA repair response is associated with normal aging, but defective repair in brain cells can contribute to neurological dysfunction. The requirement for BER in proliferating cells also correlates with high levels of many of the BER enzymes in neurogenesis after DNA damage. However, the pathway is also necessary for normal neural maintenance as larger infarct volumes after ischemic stroke are seen in some glycosylase deficient animals. Further, the requirement for DNA polymerase in post-mitotic BER is potentially more important than in proliferating cells due to reduced levels of replicative polymerases. The BER response may have particular relevance for the onset and progression of many neurodegenerative diseases associated with an increase in oxidative stress including Alzheimer's, which we are pursuing. Genetic and environmental factors likely influence DNA repair capacity. In order to gain more insight into the genetic and environmental contribution to the molecular basis of DNA repair, we have performed a human twin study, where we focused on the consequences of some of the most abundant types of DNA damage (single-strand breaks), and some of the most hazardous lesions (DNA double-strand breaks). DNA damage signaling response (Gamma-H2AX signaling), relative amount of endogenous damage, and DNA-strand break repair capacities were studied in peripheral blood mononuclear cells from 198 twins (94 monozygotic and 104 dizygotic). We did not detect genetic effects on the DNA-strand break variables in our study. In another study, we focused on potential age-associated changes in DNA damage response and the capacities of repairing DNA single-strand breaks (SSBs) and double-strand breaks (DSBs) in human peripheral blood mononuclear cells (PBMCs). Of these lesions, DSBs are the least frequent but the most dangerous for cells. We have measured the level of endogenous SSBs, SSB repair capacity, -H2AX response, and DSB repair capacity in a study population consisting of 216 individuals from a population-based sample of twins aged 40-77 years. Age in this range did not seem to have any effect on the SSB parameters. However, -H2AX response and DSB repair capacity decreased with increasing age, although the associations did not reach statistical significance after adjustment for batch effect across multiple experiments. No gender differences were observed for any of the parameters analyzed. Our findings suggest that in PBMCs, the repair of SSBs is maintained until old age, whereas the response to and the repair of DSBs decreases.