TRANSCRIPTION AND RNA BINDING IN FRAGILE X SYNDROME

脆性 X 综合征中的转录和 RNA 结合

• 批准号: 6613926
• 负责人: Daniel Reines
• 金额: $ 17.25万
• 依托单位: EMORY UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-07-01 至 2003-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6613926
• 关键词: DNA methylation; RNA binding protein; acetylation; acyltransferase; chemical structure function; chromatin; fragile X syndromes; gene induction /repression; genetic promoter element; genetic regulation; histones; human genetic material tag; human tissue; immunoprecipitation; intermolecular interaction; molecular pathology; nucleic acid repetitive sequence; nucleic acid structure; patient oriented research; sex linked trait; site directed mutagenesis; transcription factor; transfection

Description: Fragile X syndrome is the most common form of inherited mental retardation. It results from loss of function of the FMR1 gene product. Virtually all cases are due to the specific transcriptional silencing of FMR1 -- hence, the syndrome can be considered a transcriptional disease. Silencing is an indirect consequence of the expansion to more than 200 copies, of a CGG repeat (normal modal size of 30) in FMR1's 5'-untranslated region. Expansion results in the aberrant de novo methylation of cytosines both in CG dinucleotides within the repeat, and in the neighboring upstream CpG islands in the FMR1 promoter. Hypermethylation is thought to be a proximal cause of the transcriptional inactivity of FMR1 in patients. However the molecular mechanism by which methylation leads to loss of transcription of FMR1 is unknown. Patient FMR1 is packaged in hypoacetylated histones H3 and H4, another characteristic of transcriptionally silent loci. Drugs that reverse the methylation state of FMR1 DNA result in a relative hyperacetylation of histones H3 and H4 at FMR1 and restore transcription. A current model of methylation-mediated gene repression suggests that recruitment of histone deacetylases to the promoter via methyl cytosine binding proteins establish a closed chromatin environment at mutant FMR1. The long range objective of this project is to understand the molecular mechanism of transcriptional silencing of patient FMR1, and to ultimately reverse it. Aim 1 will characterize transcription factors, including histone acetyltransferase activities, that drive normal FMR1 promoter function. Aim 2 will identify repression complexes that bind methylated DNA and deacetylate histones in mutant, expanded FMR1 alleles. Aim 3 will test the idea that histone acetylation is important for FMR1 transcription by exogenously expressing histone acetyltransferase and directing it to the mutant, methylated FMR1 promoter. Promoter occupancy will be evaluated in patient cells with intermediate states of remodeled chromatin. Results obtained from this experimental system will allow identification of the steps involved in transcription of a clinically important gene residing in its natural chromosomal context.

描述：脆性 X 综合征是遗传性精神疾病最常见的形式 迟缓。它是由 FMR1 基因产物功能丧失所致。 几乎所有病例都是由于 FMR1 的特异性转录沉默所致 ——因此，该综合征可以被认为是一种转录性疾病。沉默 是 CGG 扩展到 200 多个副本的间接结果 FMR1 的 5'-非翻译区重复（正常模式大小为 30）。扩张 导致 CG 中胞嘧啶的异常从头甲基化 重复内以及邻近上游 CpG 岛中的二核苷酸 在 FMR1 启动子中。超甲基化被认为是导致 患者体内 FMR1 转录失活。然而分子 甲基化导致 FMR1 转录丢失的机制是 未知。患者 FMR1 包装在低乙酰化组蛋白 H3 和 H4 中， 转录沉默位点的另一个特征。逆转药物 FMR1 DNA 的甲基化状态导致相对超乙酰化 FMR1 处的组蛋白 H3 和 H4 并恢复转录。目前的型号为 甲基化介导的基因抑制表明组蛋白的募集 通过甲基胞嘧啶结合蛋白对启动子进行脱乙酰酶建立 突变体 FMR1 的封闭染色质环境。本次活动的长远目标 项目是了解转录沉默的分子机制 患者 FMR1，并最终逆转它。目标 1 将表征 转录因子，包括组蛋白乙酰转移酶活性， 驱动正常的 FMR1 启动子功能。目标 2 将识别压抑复合体 结合甲基化 DNA 并在突变、扩展的 FMR1 中使组蛋白脱乙酰 等位基因。目标 3 将检验组蛋白乙酰化对于 通过外源表达组蛋白乙酰转移酶进行 FMR1 转录 将其导向突变的甲基化 FMR1 启动子。促销员入住率将 在具有重构染色质中间状态的患者细胞中进行评估。 从该实验系统获得的结果将允许识别 涉及临床重要基因转录的步骤 它的自然染色体背景。