The role of p53 in remodeling DNA methylation in cancer

p53 在重塑癌症 DNA 甲基化中的作用

• 批准号: 7038307
• 负责人: SHIRLEY M TAYLOR
• 金额: $ 25.16万
• 依托单位: VIRGINIA COMMONWEALTH UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-04-01 至 2009-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7038307
• 关键词: CpG islands; DNA methylation; astrocytes; carcinogenesis; cell transformation; chromatin immunoprecipitation; fibroblasts; gene expression; gene induction /repression; gene targeting; genetic promoter element; genetically modified animals; glioma; human tissue; laboratory mouse; mass spectrometry; methylguanine DNA methyltransferase; microarray technology; neoplasm /cancer genetics; neoplastic process; p53 gene /protein; small interfering RNA; tissue /cell culture; tumor suppressor genes

DESCRIPTION (provided by applicant): The pattern of methylation of genomic DNA becomes significantly altered during oncogenesis. In human tumors, the overall level of DNA-cytosine methylation is decreased, but CpG islands generally become hypermethylated, resulting in frequent epigenetic inactivation of tumor suppressor genes. One of the most common observations is that one allele of a tumor suppressor gene becomes mutated or lost, and the other allele becomes silenced by hypermethylation. Little is known of the events that trigger this aberrant de novo methylation, nor of is it known which of the three characterized DNA methyltransferases is responsible. It is however, well recognized that the methylation machinery must be under strict regulatory control during development, and that the balance of factors involved in this regulation appears to be disrupted during tumorigenesis. The tumor suppressor gene, p53 is mutated or lost in more than 50% of all types of human tumors, and appears to be an early event in tumorigenesis in many cases. We have recently found that p53 binds the DNA methyltransferase 1 (Dnmt1) promoter in the absence of stimuli that activate p53, that activation of p53 reduces this binding, and that loss of p53 function induces upregulation of Dnmt1. These data suggest that aberrant genomic methylation might be promoted by alteration or loss of this important cancer gene. We now propose to determine the underlying mechanism of p53-mediated control of DNA methyltransferase1, its generality to the related DNA methyltransferases, and its role in the loss of tumor suppressor gene function during carcinogenesis. We propose to study the interaction of wild type and mutant p53s with the promoter regions of the Dnmt loci both in vitro and in vivo, using chromatin immunoprecipitation, to modulate the levels of p53 and Dnmts using siRNA technology, and to study the composition of protein complexes involving p53 and its mutant forms resident on the promoters of the Dnmt genes using tandem mass spectrometry. These studies will lead to an understanding of the early events in tumor progression that result in disruption of the control of DNA methylation. The inappropriate tumor suppressor gene silencing that follows this loss of control appears to be critical in promoting oncogenesis.

描述（由申请人提供）：基因组 DNA 的甲基化模式在肿瘤发生过程中发生显着改变。 在人类肿瘤中，DNA-胞嘧啶甲基化的总体水平降低，但 CpG 岛通常变得高度甲基化，导致肿瘤抑制基因频繁表观遗传失活。 最常见的观察结果之一是肿瘤抑制基因的一个等位基因发生突变或丢失，而另一个等位基因因高甲基化而沉默。 我们对触发这种异常从头甲基化的事件知之甚少，也不知道三种特征性 DNA 甲基转移酶中的哪一种负责。 然而，众所周知，甲基化机制在发育过程中必须受到严格的调节控制，并且参与这种调节的因素的平衡似乎在肿瘤发生过程中被破坏。肿瘤抑制基因 p53 在超过 50% 的所有类型人类肿瘤中发生突变或丢失，并且在许多情况下似乎是肿瘤发生的早期事件。 我们最近发现，在没有激活 p53 的刺激的情况下，p53 会结合 DNA 甲基转移酶 1 (Dnmt1) 启动子，p53 的激活会减少这种结合，而 p53 功能的丧失会诱导 Dnmt1 的上调。这些数据表明，这一重要癌症基因的改变或丢失可能会促进异常的基因组甲基化。 我们现在建议确定 p53 介导的 DNA 甲基转移酶 1 控制的潜在机制、其对相关 DNA 甲基转移酶的普遍性，以及其在癌发生过程中肿瘤抑制基因功能丧失中的作用。 我们建议在体外和体内研究野生型和突变型p53与Dnmt基因座启动子区域的相互作用，使用染色质免疫沉淀，使用siRNA技术调节p53和Dnmt的水平，并研究蛋白质的组成使用串联质谱法分析涉及 p53 及其驻留在 Dnmt 基因启动子上的突变体形式的复合物。 这些研究将有助于了解肿瘤进展中导致 DNA 甲基化控制破坏的早期事件。这种失控后出现的不适当的肿瘤抑制基因沉默似乎对于促进肿瘤发生至关重要。