Chromatin Dynamics and Genome Regulation

在哺乳动物发育过程中，染色质的动态调节允许 一个基因组中有超过200种不同的细胞除了翻译后修饰 选择性地将组蛋白变体掺入染色质中， 表观遗传调控的复杂性。例如，组蛋白变体H3.3不同于典型的H3 只有4 - 5个氨基酸，但显示出独特的基因组和发育富集 特性.虽然长期以来与基因激活有关，但最近的研究表明，H3.3 在不同的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及其相关蛋白突变的鉴定 癌症，包括小儿胶质母细胞瘤和胰腺神经内分泌肿瘤， 强调了迫切需要了解这种组蛋白变体在发育过程中的作用， 上下文尽管越来越感兴趣，H3.3如何独特地促进染色质的功能 是一个长期悬而未决的问题我们提出了一个创新的方案 结合小鼠遗传学、生物化学、化学生物学和尖端基因组学， 了解H3.3介导的染色质动力学的功能相关性。我们的中央 假设H3.3沉积促进了独特的发育 调节染色质景观，允许做出适当的细胞命运决定。我们 初步数据表明核小体更新速率在没有H3.3的情况下降低， 并且H3.3动力学可以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在促进特定组蛋白翻译后修饰状态中的功能，（2）鉴定 控制H3.3在特定基因组位点沉积的调节机制， 组蛋白变体在两个已知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的能力中的重要性， 在早期胚胎的细胞命运转变过程中结合靶调控元件。我们提出的 这项研究意义重大，因为它将确定染色质变异体是 细胞命运的转变，并作为一个平台，以了解细胞身份的表观遗传调控 在体内平衡，以及发育失调和疾病状态中。

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.