Chromatin Dynamics and Genome Regulation

哺乳动物的发育导致从单个基因组中指定超过200种不同的细胞类型， 随后在成年生物体中维持细胞身份。真核细胞的基因组被包装成 一种动态的染色质结构，它允许细胞控制所有DNA编码信息的可及性。 特化组蛋白或变体选择性地掺入到这种动态的基因组结构中， 表观遗传调控的一个重要特征。我的实验室的一个主要重点是这样一种蛋白质，组蛋白变体 H3.3。人类癌症和发育中H3.3和相关蛋白突变的鉴定 这些疾病的发生，增加了了解这种组蛋白变异体在正常组织中作用的迫切需要。 发育和成人体内平衡。虽然H3.3在多种情况下对细胞功能至关重要，但H3.3如何影响细胞功能？ 对染色质功能的独特贡献是该领域长期存在的未回答的问题。而长 与基因激活相关，最近的研究表明H3.3也沉积在重复的异染色质， 区域的基因组，沉积在每个区域促进独立的伴侣复合物。我们 我仍然不知道H3.3是如何在它的两个伴侣复合物之间分配的，或者这种平衡是如何形成的。 影响细胞功能。一旦沉积，我们的研究和其他人已经证明H3.3影响 常染色质和异染色质的染色质修饰景观。我们的数据表明，H3.3 可以通过磷酸化一种独特的丝氨酸直接在常染色质上发挥这种功能， 组蛋白乙酰转移酶的活性或通过分子伴侣介导的募集间接作用于异染色质 辅阻遏物复合体的一部分尽管有这些有趣的观察，我们还没有完全理解 H3.3沉积影响染色质状态的机制。最后，我们不明白H3.3如何 在复杂的多细胞生物体中发挥着无数的功能。本提案的目标是 目的：（1）了解H3.3分子伴侣复合物平衡是如何建立的，并确定 （2）确定H3.3影响局部细胞功能的分子机制 染色质景观，以及这些事件如何影响下游基因组的使用，以及（3）利用我们的 新的小鼠模型，以了解H3.3在成体生物体中的作用，包括成体干细胞。我们 拟议的研究是重要的，因为它将作为一个平台，了解细胞的表观遗传调控 在正常发育和成人体内平衡中的同一性，以及由此延伸的发育失调 和疾病状态。

Mammalian development results in the specification of over 200 different cell types from a single genome, with subsequent maintenance of cell identity in adult organisms. The genomes of eukaryotic cells are packaged into a dynamic chromatin structure, which allows cells to control the accessibility of all DNA encoded information. The selective incorporation of specialized histone proteins, or variants, into this dynamic genomic structure is an important feature of epigenetic regulation. A main focus of my lab is one such protein, the histone variant H3.3. The identification of mutations in H3.3 and associated proteins in human cancers and developmental disorders has heightened the pressing need to understand the role of this histone variant in normal development and adult homeostasis. Although H3.3 is critical to cellular function in multiple contexts, how H3.3 contributes uniquely to chromatin function is a long-standing, unanswered question in the field. While long associated with gene activation, recent studies establish that H3.3 also deposited at repetitive, heterochromatic regions of the genome, with deposition at each region facilitated by independent chaperone complexes. We still do not know how H3.3 is partitioned between its two chaperone complexes, or how this equilibrium influences cellular function. Once deposited, our studies and others have demonstrated that H3.3 influences the chromatin modification landscape at both euchromatin and heterochromatin. Our data suggest that H3.3 can perform this function directly at euchromatin via phosphorylation of a unique serine that influences the activity of a histone acetyltransferase or indirectly at heterochromatin through chaperone-mediated recruitment of a co-repressor complex. Despite these intriguing observations, we do not yet fully understand the detailed mechanisms by which H3.3 deposition influences chromatin states. Finally, we do not understand how H3.3 performs its myriad functions in the context of complex, multicellular organisms. The goals of this proposal are to: (1) understand how H3.3 chaperone complex equilibrium is established, and determine the effects of disequilibrium on cell function, (2) determine the molecular mechanisms by which H3.3 influences local chromatin landscapes, and how these events influence downstream genome usage, and (3) make use of our novel mouse models to understand the role of H3.3 in adult organisms, including adult stem cells. Our proposed research is significant because it will serve as a platform to understand epigenetic regulation of cell identity in both normal development and adult homeostasis, and by extension, developmental misregulation and disease states.