Chromatin targeting and transcriptional control by the histone variant H2A.Z

组蛋白变体 H2A.Z 的染色质靶向和转录控制

• 批准号: 10159947
• 负责人: Roger Bancroft Deal
• 金额: $ 30.47万
• 依托单位: EMORY UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-07-19 至 2023-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10159947
• 关键词: Ablation; Activation Analysis; Address; Affect; Animals; Arabidopsis; Arabidopsis Proteins; Arginine; Back; Binding; Binding Sites; Biological; Biological Models; Breast Cancer Cell; Cancer Control; Cell Proliferation; Cells; ChIP-seq; Chromatin; Chromatin Remodeling Factor; Complement; Complex; Culture Media; DNA Binding Domain; Data; Defect; Deposition; Development; Developmental Process; Disease; Embryonic Development; Epigenetic Process; Essential Genes; Eukaryota; Event; Gene Expression Regulation; Gene Silencing; Genes; Genetic; Genetic Transcription; Genome; Genomic Segment; Genomics; Goals; Hair Root; Heterochromatin; Histone H2A; Histone H3; Histones; Homing; Individual; Laboratories; Lysine; Maintenance; Malignant Neoplasms; Malignant neoplasm of pancreas; Mediating; Mouse-ear Cress; Nucleosomes; PRC1 Protein; Phase; Plant Model; Plants; Play; Point Mutation; Polycomb; Process; Protein Family; Proteins; Public Health; Regulator Genes; Research; Resolution; Role; Shapes; Site; Specific qualifier value; Starvation; System; Testing; Time; Transcriptional Activation; Transcriptional Regulation; Variant; Work; base; cancer cell; cancer therapy; cell type; design; epigenomics; experimental study; genome-wide; histone modification; inorganic phosphate; insight; mutant; novel strategies; operation; prevent; response; targeted cancer therapy; tool; transcriptomics

PROJECT SUMMARY The epigenetic system is essential for specifying cell fates during development because it is used to select and reinforce the portions of the genome that will be expressed or silenced in a given cell type. The highly conserved histone H2A variant, H2A.Z, is a key component of this system that is required for embryonic development in animals and regulates many developmental processes in plants. Research has focused on H2A.Z because it has been suggested to play a causal role in both pancreatic and breast cancer cell proliferation, yet its function remains poorly understood. H2A.Z is selectively deposited into chromatin by the SWR1 remodeling complex at thousands of genes, where it paradoxically promotes the transcription of some genes, while silencing others. Despite the biological importance of this histone variant, key questions regarding its targeting and function persist. For example: how is the SWR1 complex targeted to specific genomic sites for H2A.Z deposition? What are the mechanisms by which H2A.Z represses transcription? Given that plants have historically been a rich model system to inform animal epigenetics and that, unlike animals, H2A.Z-deficient plants are viable, our goal is to use the powerful experimental tools available in the model plant Arabidopsis thaliana to answer both of these questions. We recently identified several unexpected SWR1-interacting proteins in Arabidopsis that were not previously associated with H2A.Z deposition, including methyl-CpG- binding domain 9 (MBD9) and several other proteins known to bind nucleosomes. We have now observed that MBD9 is required for H2A.Z incorporation at a subset of H2A.Z-enriched sites that share a common histone modification profile, suggesting that MBD9 and other SWR1-associated proteins provide specific homing functions for SWR1. In Aim 1, we will define the roles of these proteins in H2A.Z targeting in order to understand the mechanisms that shape the genomic distribution of this variant. Regarding transcription, we have recently found that H2A.Z is required for gene silencing by the conserved polycomb system. Among the genes that require H2A.Z and the polycomb system for silencing are the Phosphate Starvation Response genes, which can be rapidly converted from silent to active and back again by shifting plants between phosphate-rich and phosphate-depleted growth media. In Aim 2 we will take advantage of this inducible and repressible system to define the order of events that occur during H2A.Z-mediated polycomb silencing in the root hair cell type, where phosphate concentration changes are first detected by the plant. We will follow these studies with inducible genetic ablation of various players during the establishment or maintenance phases of silencing in order to define the role H2A.Z in gene silencing. The powerful genetic tools available in Arabidopsis provide a unique opportunity to understand the mechanisms of H2A.Z targeting and function, and we anticipate that this work will advance the field by answering long-standing questions about histone variant function. Our results may also provide rationale for manipulation of H2A.Z as a target for cancer therapy.

项目总结 表观遗传系统在发育过程中决定细胞命运是必不可少的，因为它被用来选择和 加强在特定细胞类型中表达或沉默的基因组部分。高度的 保守的组蛋白H_2A变异体H_2A.Z是该系统的关键组成部分，是胚胎发育所必需的 在动物中的发育，并调节植物的许多发育过程。研究的重点是 因为它被认为在胰腺癌细胞和乳腺癌细胞中都起到了因果作用 然而，人们对其功能仍知之甚少。H_2A.Z被选择性地沉积到染色质中 SWR1在数千个基因上重塑复合体，在那里它矛盾地促进一些基因的转录 基因，同时让其他人沉默。尽管这种组蛋白变体具有重要的生物学意义，但关于 它的目标和功能一直存在。例如：SWR1复合体如何靶向特定的基因组位置 H_2A.Z证词？H2A.Z抑制转录的机制是什么？考虑到植物有 从历史上看，这是一个丰富的模型系统，可以告知动物表观遗传学，而且与动物不同的是，缺乏H2A.Z 植物是可行的，我们的目标是使用模式植物拟南芥中可用的强大实验工具 Taliana回答了这两个问题。我们最近发现了几个意想不到的SWR1相互作用 拟南芥中以前与H2A.Z沉积无关的蛋白质，包括甲基-CpG- 结合结构域9(MBD9)和其他几种已知与核小体结合的蛋白质。我们现在已经观察到 在具有共同组蛋白的富含H_2A.Z的位点的子集上，需要MBD9来掺入H_2A.Z 修饰谱，表明MBD9和其他SWR1相关蛋白提供特定的归巢 用于SWR1的函数。在目标1中，我们将定义这些蛋白质在H2A.Z靶向中的作用，以便 了解塑造这种变异的基因组分布的机制。关于抄写，我们 最近发现，在保守的多梳系统中，基因沉默需要H_2A.Z。在这些人中 需要H2A.Z和用于沉默的多梳系统的基因是磷酸饥饿反应 基因，可以通过在植物之间转移，迅速从沉默转化为活跃，然后再转化回来 富磷和缺磷生长介质。在目标2中，我们将利用这种诱导性和 可抑制系统，用于定义在H.A.Z介导的多梳沉默期间发生的事件的顺序 根毛细胞类型，其中磷浓度的变化是由植物首先检测到的。我们将遵循这些原则 不同参与者在建立或维持阶段可诱导基因消融的研究 沉默，以确定H2A.Z在基因沉默中的作用。中提供的功能强大的遗传工具 拟南芥为理解H2A.Z靶向和功能的机制提供了一个独特的机会。 我们预计这项工作将通过回答长期存在的关于组蛋白变体的问题来推动这一领域的发展 功能。我们的结果也可能为操纵H_2A.Z作为癌症治疗的靶点提供理论依据。