(PQA2) Impact of obesity on endogenous mutational hotspots

描述(由申请人提供)：这项建议的总体目标是了解饮食能量平衡，特别是肥胖如何影响内源性突变“热点”的基因组稳定性。为了实现这一目标，我们将使用一种新的小鼠模型来确定肥胖对这些小鼠不同组织中DNA结构诱导的突变的影响。重复的DNA序列广泛分布于哺乳动物基因组中，可以采用替代的(非B-DNA)二级结构，如H-DNA。重要的是，这些非B DNA结构形成序列经常与人类基因组中的内源性突变“热点”共定位，这意味着它们与癌症病因学有关。例如，c-myc基因中的H-DNA形成序列在Burkitt淋巴瘤和急性B细胞淋巴瘤的易位断裂“热点”处被发现。我们开发了一种新型的突变报告小鼠，其中包含一个形成人H-DNA的c-myc序列，该序列与Burkitt淋巴瘤中的易位断点“热点”共定位，并首次证明这些序列在活体动物中是突变的。众所周知，肥胖会增加细胞的氧化应激和DNA氧化损伤，而限制卡路里摄入则表明可以减少细胞的氧化应激、氧化DNA损伤、减少突变和增强DNA修复途径。此外，肥胖是包括白血病和淋巴瘤在内的大量男性和女性癌症的重要风险因素。然而，饮食能量平衡，特别是肥胖对DNA结构诱导的遗传不稳定性的影响程度尚不清楚。因此，拟议工作的一个目标是填补这一知识空白。在这项提案中，我们将检验肥胖会增加DNA结构导致的遗传不稳定性这一工作假说。我们将研究饮食诱导肥胖(DIO)对我们的新型突变报告鼠DNA结构诱导突变的影响。将对这些小鼠的几种不同组织进行评估，以确定对DIO的反应是否存在组织特异性差异。我们还将探索任何观察到的肥胖对DNA结构诱导的遗传不稳定的影响的潜在机制。我们将重点研究肥胖对DNA修复机制的影响，因为最近的几项研究表明，肥胖会损害多条DNA修复途径，包括非同源末端连接，这是一种我们发现在哺乳动物细胞H-DNA结构处理中发挥作用的修复途径。这项拟议研究的完成将使人们更好地理解肥胖如何影响癌症的发展。此外，这项工作将有助于确定预防和/或治疗肥胖相关癌症的新靶点。

DESCRIPTION (provided by applicant): The overall objective of this proposal is to understand how dietary energy balance and especially obesity influences genome stability at endogenous mutational "hotspots". To achieve this objective, we will use a novel mouse model 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. Importantly, these non-B DNA structure- forming sequences often co-localize with endogenous mutational "hotspots" in the human genome, 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 a human H-DNA-forming c-MYC sequence that co-localizes with a translocation breakpoint "hotspot" in Burkitt's lymphoma, and demonstrated for the first time that these sequences are mutagenic in living animals. 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 in both men and women, including leukemias and lymphomas. 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 ths proposal, we will test the working hypothesis that obesity increases DNA structure-induced genetic instability. We will examine the impact of diet-induced obesity (DIO) on DNA structure-induced mutagenesis in our novel mutation reporter mice. Several different tissues will be evaluated from these mice to determine whether there are any tissue specific differences in response to DIO. We will also explore potential mechanisms for any observed effects 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 H-DNA structures in mammalian cells. Completion of the proposed studies will lead to a greater understanding of how obesity influences cancer development. In addition, this work will lead to the identification of novel targets for the prevention and/or treatment of obesity-related cancers.