Mechanisms of Obesity-Induced Genetic Instability at Endogenous Mutation Hotspots

项目摘要 这项建议的总体目标是了解饮食能量平衡，特别是肥胖 影响内源突变“热点”的基因组稳定性。为了实现这一目标，我们将使用新的 我们已经开发了小鼠模型来确定肥胖对DNA结构诱导的 在这些小鼠的各种组织中的诱变。重复的DNA序列广泛分布在 哺乳动物基因组，并可以采用替代（非B DNA）二级结构，如H-DNA和Z- DNA.重要的是，这些非B DNA结构形成序列在内源性DNA中显著富集。 人类癌症基因组中的突变热点，将其与癌症病因学联系起来。例如，H-DNA- 在伯基特淋巴瘤的易位断裂热点发现c-MYC基因中的形成序列， 急性B细胞淋巴瘤我们已经开发了新的突变报告小鼠含有人类H-DNA-和Z- 与易位断裂点热点共定位的DNA形成序列，并首次证明了 这些序列在体内致突变的时间。已知肥胖会增加细胞氧化应激， 氧化性DNA损伤，而热量限制已显示出降低细胞氧化应激， 氧化DNA损伤，减少诱变和增强DNA修复途径。此外，肥胖是一种 是许多癌症的重要危险因素。然而，膳食能量平衡的程度 特别是肥胖影响DNA结构诱导的遗传不稳定性是未知的。因此， 拟议的工作是填补这一知识空白。在这个提议中，我们将检验肥胖症 增加DNA结构引起的遗传不稳定性。我们将研究饮食引起的肥胖的影响， 热量限制对小鼠DNA结构诱发突变的影响。将评价几种不同的组织 以确定是否有任何组织特异性差异的诱变反应， 能量平衡控制我们还将探索肥胖对DNA结构影响的机制- 导致遗传不稳定。我们将集中研究肥胖对DNA修复机制的影响， 最近的几项研究表明，肥胖损害了多种DNA修复途径，包括非- 同源末端连接，我们发现这是一种在非B DNA加工中起作用的修复途径。在 此外，我们还发现侧翼核酸内切酶1（FEN 1）在无错误加工中起着重要作用。 非B DNA，其水平受膳食能量平衡调节。这些观察也将 在本提案中进行了更详细的探讨。完成拟议的研究将导致 了解肥胖如何影响癌症病因。此外，这项工作将导致查明 用于预防和/或治疗肥胖相关癌症的新靶点。

PROJECT SUMMARY The overall objective of this proposal is to understand how dietary energy balance and especially obesity influences genome stability at endogenous mutation “hotspots”. To achieve this objective, we will use novel mouse models that we have developed to determine the impact of obesity on DNA structure-induced mutagenesis in various tissues from these mice. Repetitive DNA sequences are widely dispersed throughout mammalian genomes and can adopt alternative (non-B DNA) secondary structures, such as H-DNA and Z- DNA. Importantly, these non-B DNA structure-forming sequences are significantly enriched at endogenous mutation hotspots in human cancer genomes, implicating them in cancer etiology. For example, H-DNA- forming sequences in the c-MYC gene are found at translocation breakage hotspots in Burkitt’s lymphoma and acute B-cell lymphoma. We have developed novel mutation-reporter mice containing human H-DNA- and Z- DNA-forming sequences that co-localize with translocation breakpoint hotspots, and demonstrated for the first time that these sequences are mutagenic in vivo. Obesity is known to increase cellular oxidative stress and oxidative DNA damage, whereas calorie restriction has been shown to decrease cellular oxidative stress, oxidative DNA damage, reduce mutagenesis and to enhance DNA repair pathways. In addition, obesity is an important risk factor for a significant number of cancers. However, the extent to which dietary energy balance and especially obesity influences DNA structure-induced genetic instability is not known. Thus, a goal of the proposed work is to fill this gap in knowledge. In this proposal, we will test the working hypothesis that obesity increases DNA structure-induced genetic instability. We will examine the impact of diet-induced obesity and calorie restriction on DNA structure-induced mutagenesis in mice. Several different tissues will be evaluated from these mice to determine whether there are any tissue specific differences in mutagenesis in response to energy balance manipulation. We will also explore mechanisms for the impact of obesity on DNA structure- induced genetic instability. We will focus our studies on the impact of obesity on DNA repair mechanisms as several recent studies have suggested that obesity impairs multiple DNA repair pathways, including non- homologous end-joining, a repair pathway that we have found to play a role in the processing of non-B DNA. In addition, we have found that flap endonuclease 1 (FEN1) plays an important role in error-free processing of non-B DNA and that its levels are modulated by dietary energy balance. These observations will also be explored in more detail in this proposal. Completion of the proposed studies will lead to a greater understanding of how obesity influences cancer etiology. In addition, this work will lead to the identification of novel targets for the prevention and/or treatment of obesity-related cancers.