Toxin-Associated Oxidative DNA Damage Initiates Tumor-Specific Epigenetic Changes

描述（由申请人提供）：在本项目中，目的是了解暴露于环境毒素导致疾病特异性表观遗传变化的机制。虽然已经研究了对有毒物质和毒素暴露的表观遗传变化，但这些研究中的大多数都研究了DNA甲基化的变化，这被认为是后来更永久的表观遗传变化。在与毒素暴露有关的肿瘤发生过程中，异常的DNA超甲基化使肿瘤抑制基因的表达沉默。特别是了解急性暴露导致疾病形成的表观遗传变化的起始、时间和分子进展，将使我们能够制定更好的预防和治疗由环境暴露引起的疾病的策略。我们已经在体外证明，暴露于氧化损伤会导致表观遗传沉默蛋白的染色质结合在全基因组范围内发生急性变化，这表明表观遗传变化可能通过一种机制启动。在这里，我们使用暴露于产毒素细菌，肠产毒素脆弱拟杆菌（ETBF），已知与人类急性和慢性结肠炎和结肠癌相关，在小鼠模型中诱导结肠炎症，随后发生肿瘤。因此，了解这些细菌引起的表观遗传变化背后的机制将与人类疾病有关。此外，由于与许多毒物和其他毒素一样，暴露于ETBF会导致炎症和相关氧化损伤的增加，因此我们模型的发现可以转化为导致人类疾病的许多不同暴露。本应用程序的目的是了解毒素暴露如何引发疾病特异性表观遗传变化，包括这些变化的时间和分子进展。利用ETBF感染，我们将确定急性毒素暴露是否会导致表观遗传沉默蛋白的染色质结合在全基因组范围内发生变化，以及这种结合变化是否依赖于氧化DNA损伤。此外，利用炎症诱导肿瘤发生的ETBF模型，我们将研究这些急性表观遗传变化是否会导致疾病特异性表观遗传变化，并研究从特定基因启动子处表观遗传沉默蛋白的富集到这些启动子的DNA甲基化的分子进展。

DESCRIPTION (provided by applicant): In this project, the intent is to understand the mechanism by which exposure to an environmental toxin causes disease-specific epigenetic changes. While epigenetic changes in response to toxicant and toxin exposure have been studied, the majority of these studies have examined changes in DNA methylation, which is thought to be a later more permanent epigenetic change. During tumorigenesis, which has been linked to toxin exposure, aberrant DNA hypermethylation silences the expression of tumor suppressor genes. Specifically understanding the initiation, timing, and molecular progression of epigenetic changes from acute exposure to disease formation will allow us to develop better prevention and treatment strategies for diseases caused by environmental exposure. We have demonstrated in vitro that exposure to oxidative damage causes acute genome-wide changes in the chromatin binding of epigenetic silencing proteins, suggesting a mechanism by which epigenetic changes may be initiated. Here we use exposure to toxigenic bacteria, enterotoxigenic Bacteroides fragilis (ETBF), which is known to be associated with acute and chronic colitis and colon cancer in humans, to induce colon inflammation followed by tumorigenesis in a mouse model. Therefore, understanding the mechanism behind epigenetic changes induced by these bacteria will be relevant to human disease. Furthermore, because like many toxicants and other toxins, exposure to ETBF causes an increase in inflammation and associated oxidative damage, the findings from our model can be translated to many different exposures that cause human disease. The goal of this application is to understand how toxin exposure initiates disease-specific epigenetic changes, including the timing and molecular progression of such changes. Using ETBF infection, we will determine if acute toxin exposure results in genome-wide changes in the chromatin binding of epigenetic silencing proteins and if this change in binding is dependent on oxidative DNA damage. Furthermore, using the ETBF model of inflammation-induced tumorigenesis we will investigate if these acute epigenetic changes result in disease-specific epigenetic changes as well as study the molecular progression from the enrichment of epigenetic silencing proteins at specific gene promoters to DNA methylation of those promoters.