Chromatin Dynamics and Genome Regulation

哺乳动物发育过程中染色质的动态调节允许规范 来自单个基因组的200多种不同的细胞类型。除了翻译后修改之外 在组蛋白蛋白中，选择性地将组蛋白变体掺入染色质中会增加 表观遗传调控的复杂性。例如，组蛋白变异体H3.3不同于典型的H3 只有4-5个氨基酸，但显示出明显的基因组和发育丰富 属性。虽然长期以来与基因激活有关，但最近的研究表明，H3.3具有 不同基因组区域中的多种功能并不总是与活性相关 染色质状态。人类H3.3基因及其相关蛋白突变的鉴定 癌症，包括儿童胶质母细胞瘤和胰腺神经内分泌肿瘤， 迫切需要了解这种组蛋白变体在发育过程中的作用 背景。尽管人们对H3.3的兴趣与日俱增，但H3.3如何对染色质的功能做出独特贡献 是该领域一个长期悬而未决的问题。我们提出了一个创新的计划 将小鼠遗传学、生物化学、化学生物学和尖端基因组学结合起来 了解H3.3介导的染色质动力学的功能相关性。我们的中央 假说是H3.3的沉积促进了独特发育的建立 受调控的染色质景观，允许做出适当的细胞命运决定。我们的 初步数据表明，在没有H3.3的情况下，核小体周转率降低， 而H3.3的动力学可能促进组蛋白在特定的翻译后修饰状态 基因组区域。在我们的研究过程中，我们将(1)定义潜在的机制 H3.3在促进特定的组蛋白翻译后修饰状态中的作用，(2)识别 控制H3.3在特定基因组位点沉积的调控机制，以及 组蛋白变体在两个已知的伴侣系统之间的分布，以及(3)确定 染色质动力学在谱系特异性转录因子能力中的重要性 在早期胚胎的细胞命运转变过程中结合靶调控元件。我们的建议 这项研究意义重大，因为它将建立染色质变体作为 细胞命运的转变，并作为一个平台来理解细胞身份的表观遗传调控 既有动态平衡，也有发育失调和疾病状态。

Dynamic regulation of chromatin during mammalian development allows the specification of over 200 different cell types from a single genome. In addition to post-translational modification of histone proteins, selective incorporation of histone variants into chromatin adds to the complexity of epigenetic regulation. For example, histone variant H3.3 differs from canonical H3 by only 4-5 amino acids, yet displays distinct genomic and developmental enrichment properties. While long associated with gene activation, recent studies suggest that H3.3 has multiple functions in distinct genomic regions that are not always correlated with an active chromatin state. The identification of mutations in H3.3 and associated proteins in human cancers, including pediatric glioblastomas and pancreatic neuroendocrine tumors, has heightened the pressing need to understand the role of this histone variant in a developmental context. Despite increased interest, how H3.3 contributes uniquely to the function of chromatin is a long-standing, unanswered question in the field. We propose an innovative program combining mouse genetics, biochemistry, chemical biology, and cutting-edge genomics to understand the functional relevance of H3.3-mediated chromatin dynamics. Our central hypothesis is that H3.3 deposition promotes the establishment of unique developmentally regulated chromatin landscapes that allow appropriate cell fate decisions to be made. Our preliminary data suggests that nucleosome turnover rates are reduced in the absence of H3.3, and that H3.3 dynamics may facilitate histone post-translational modification states at specific genomic regions. Over the course of our studies we will (1) define the mechanisms underlying H3.3 function in promoting specific histone post-translational modification states, (2) identify regulatory mechanisms that control deposition of H3.3 at specific genomic loci, and the distribution of the histone variant between the two known chaperone systems, and (3) determine the importance of chromatin dynamics in the ability of lineage-specific transcription factors to bind target regulatory elements during cell fate transitions in the early embryo. Our proposed research is significant because it will establish chromatin variants as necessary components of cell fate transitions, and serve as a platform to understand epigenetic regulation of cell identity in both homeostasis, but also developmental misregulation and disease states.