Epigenetic Mechanisms of Oncohistone Detoxification

肿瘤组蛋白解毒的表观遗传机制

• 批准号: 9124149
• 负责人: Katharine Diehl
• 金额: $ 5.25万
• 依托单位: PRINCETON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-04-01 至 2019-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9124149
• 关键词: Abate; Acetylation; Affect; Amines; Antibodies; Biology; CRISPR/Cas technology; Cancerous; Cell Line; Cell physiology; Cells; ChIP-seq; Chemicals; Childhood Brain Neoplasm; Childhood Malignant Brain Tumor; Chromatin; Complex; DNA; Detection; Development; Diffuse; Drug Metabolic Detoxication; Enzyme Inhibition; Enzymes; Epigenetic Process; Eukaryotic Cell; Fluorescence Resonance Energy Transfer; Future; Gene Expression; Gene Expression Regulation; Gene Silencing; Genes; Genetic Transcription; Genomics; Glean; Glioblastoma; Glioma; Goals; Histone Acetylation; Histone Deacetylase; Histone Deacetylase Inhibitor; Histones; Knock-out; Lead; Link; Lysine; Malignant Neoplasms; Mammalian Cell; Maps; Measures; Methionine; Methods; Methylation; Methyltransferase; Modification; Mutate; Mutation; Names; Nucleosomes; Optical Methods; Output; Pathogenicity; Pathway interactions; Peptides; Polycomb; Pontine structure; Population; Post-Translational Protein Processing; Proteins; Research; Role; Series; Signal Transduction; Site; Small Interfering RNA; Specificity; Tail; Technology; Testing; Therapeutic; Therapeutic procedure; Time; Toxic effect; Training; Work; base; cancer cell; cellular development; chromatin modification; combat; design; genome wide methylation; glycosylation; inhibitor/antagonist; insight; mouse model; mutant; programs; public health relevance; research study; tool

 DESCRIPTION (provided by applicant): The proposed research in this training plan will focus on investigating the mechanisms by which the toxicity of oncohistones in cells can be abated by manipulating histone post-translational modifications. In eukaryotic cells, DNA is stored as chromatin, which consists of repeating units called nucleosomes made up of DNA wrapped around histone proteins. Extending out from each histone are peptide tails that are post-translationally modified in a variety of ways, including by acetylation, methylation, glycosylation and ubiquitylation. These modifications (PTMs) modulate access to the DNA, which in turn controls transcription, replication, and other cellular processes. Importantly, misregulation of these epigenetic processes has been linked to cancer, and recently it has also been shown by our group and others that mutations in the core histone proteins are found in cancer cells. In particular, mutations in histone 3 (H3) are associated with a deadly form of pediatric brain tumor. In a majority of diffuse pontine glioblastomas (DIPGs), lysine 27 in H3 is mutated to methionine (H3K27M) in a small percentage of nucleosomes. This mutation acts as a potent inhibitor of the polycomb repressor complex 2 (PRC2), which is a methyltransferase. In general, methylation of H3K27 by PRC2 is associated with gene silencing, so reduced levels of H3K27me3 due to H3K27M lead to disruption of genomic programs and thus perturbation of cellular development. Since PRC2 is able to sense chromatin states and modulate its methyltransferase output based on those signals, we hypothesized that PRC2 inhibition could be impacted by existing PTMs on the same H3 tail (i.e. in cis). Indeed, we found that PTMs, particularly polyacetylation of H3, have been found to diminish the inhibitory effect of H3K27M peptides. Therefore, we postulate that the deliberate manipulation of PTM levels relevant to PRC2 could be used to abate the pathogenicity of H3K27M. The strategy explored in this project is to use histone deacetylase (HDAC) inhibitors to achieve elevated levels of acetylation of H3 in H3K27M mutant cells and to study the mechanisms by which this manipulation impacts the PTM cross-talks. The work described herein employs a chemical biology approach to probe specific mechanisms associated with H3K27M "detoxification" as well as to provide a better understanding of epigenetic misregulation by "oncohistones" in general. The specific aims of this project are: (1) To screen HDAC inhibitors for their effect on methyltransferase activity in cells expressing the mutant H3K27M. (2) To characterize mechanisms by which HDACs impact methyltransferase activity in cells expressing H3K27M. (3) To determine the effect of HDAC inhibitors on the pathogenicity of glioblastoma cells that express the H3K27M mutant. This research applies chemical biology tools to elucidate mechanisms by which this cancerous mutation is affected by manipulating the acetylation/methylation cross-talk in cells via HDAC inhibitors. The long term goal of performing these fundamental studies is to illuminate these interconnected PTM pathways and inform the future development of therapeutic procedures.

 描述（由申请人提供）：本培训计划中的拟议研究将侧重于研究通过操纵组蛋白翻译后修饰可以减轻细胞中致癌组蛋白毒性的机制。在真核细胞中，DNA以染色质的形式储存，染色质由称为核小体的重复单位组成，核小体由DNA包裹在组蛋白周围组成。从每个组蛋白延伸出的是肽尾，其以多种方式进行后修饰，包括通过乙酰化、甲基化、糖基化和泛素化。这些修饰（PTM）调节对DNA的访问，这反过来又控制转录，复制和其他细胞过程。重要的是，这些表观遗传过程的失调与癌症有关，最近我们的研究小组和其他人也表明，在癌细胞中发现了核心组蛋白的突变。特别是，组蛋白3（H3）的突变与一种致命的儿科脑瘤有关。在大多数弥漫性脑桥胶质母细胞瘤（DIPG）中，H3中的赖氨酸27在一小部分核小体中突变为甲硫氨酸（H3 K27 M）。这种突变作为多梳阻遏复合物2（PRC 2）的有效抑制剂，PRC 2是一种甲基转移酶。一般来说，PRC 2对H3 K27的甲基化与基因沉默相关，因此由于H3 K27 M导致的H3 K27 me 3水平降低导致基因组程序的破坏，从而干扰细胞发育。由于PRC 2能够感测染色质状态并基于这些信号调节其甲基转移酶输出，因此我们假设PRC 2抑制可能受到相同H3尾上现有PTM的影响（即顺式）。事实上，我们发现PTM，特别是H3的多乙酰化，已经发现减弱H3 K27 M肽的抑制作用。因此，我们推测，与PRC 2相关的PTM水平的故意操纵可用于减弱H3 K27 M的致病性。该项目中探索的策略是使用组蛋白脱乙酰酶（HDAC）抑制剂来实现H3 K27 M突变细胞中H3乙酰化水平的升高，并研究这种操作影响PTM交叉会谈的机制。本文所述的工作采用化学生物学方法来探测与H3 K27 M“解毒”相关的特定机制，以及提供对一般由“癌组蛋白”引起的表观遗传误调节的更好理解。本课题的具体目标是：（1）筛选HDAC抑制剂，观察其对突变型H3 K27 M表达细胞中甲基转移酶活性的影响。(2)表征HDAC影响表达H3 K27 M的细胞中甲基转移酶活性的机制。(3)确定HDAC抑制剂对表达H3 K27 M突变体的胶质母细胞瘤细胞的致病性的影响。这项研究应用化学生物学工具来阐明这种癌性突变通过HDAC抑制剂操纵细胞中的乙酰化/甲基化串扰而受到影响的机制。进行这些基础研究的长期目标是阐明这些相互关联的PTM途径，并为治疗程序的未来发展提供信息。