Factors that regulate chromatin organization and gene transcription

描述(由申请人提供)： 摘要常染色质和异染色质等染色质结构域是如何建立和维持的，人们对此知之甚少。染色质组织的核心是组蛋白，它由伴侣蛋白沉积和移除。Spt6就是这样的伴侣之一，它在进化上是保守的，并通过与RNA聚合酶II(RNAPII)C末端结构域(CTD)的相互作用促进转录延伸。在转录过程中，Spt6在转录RNAPII之后介导核小体重组，并促进H3K36甲基化，从而招募组蛋白脱乙酰酶和染色质重塑活动，维持基因编码区染色质的完整性。我们的研究现在发现Spt6是维持CTD磷酸化的一个新的调节电路的中心组件；这个电路本身通过Spt6蛋白的稳定性来控制。我们还发现，Spt6在S期表达上调，在这一关键时期，它可能参与组蛋白基因的转录和/或沉积。此外，我们还发现了Spt6在维持着丝粒特性方面的一个意想不到的作用，它通过潜在的靶向Psh1 E3连接酶来移除异位沉积的组蛋白H3变体Cse4。尽管有这些发现，但我们对Spt6如何发挥其染色质依赖的活动知之甚少。因此，这项建议旨在阐明Spt6有助于维持基因组编码区和调控区染色质结构的基本机制，从而有助于Spt6的生物学以及染色质结构域的建立和维持机制。为了实现这一目标，我们将解决以下关键问题：1)Spt6是如何通过其与RNAPII的相互作用以及该蛋白上发生的翻译后修饰来调节的？2)为什么Spt6细胞周期被调节，它在S期扮演什么角色？3)Spt6除了在转录调控中发挥典型作用外，还调控染色质生物学的其他方面，特别是着丝粒的特性？鉴于Spt6在进化过程中的保守性，我们的研究将显著影响我们对转录延长和维持染色质完整性的机制的理解，这些机制支配着基因组的完整性。这些研究也将与我们对Spt6在人类发育和疾病中的理解有关。

DESCRIPTION (provided by applicant): ABSTRACT How chromatin domains such as euchromatin and heterochromatin are established and maintained are poorly understood. At the heart of chromatin organization are the histone proteins, which are deposited and removed by chaperone proteins. One such chaperone is Spt6, which is evolutionarily conserved and promotes transcription elongation through its interaction with the RNA polymerase II (RNAPII) C-terminal domain (CTD). During transcription, Spt6 mediates nucleosome reassembly in the wake of transcribing RNAPII and promotes H3K36 methylation, which recruits histone deacetylase and chromatin remodeling activities that maintain chromatin integrity in the coding region of genes. Our studies have now identified Spt6 as a central component of a novel regulatory circuit that maintains CTD phosphorylation; this circuit is itself controlled through Spt6 protein stability. We have also found that Spt6 is up-regulated during S phase, where it likely contributes to histone gene transcription and/or deposition at this critical stage. Further, we have uncovered an unexpected role for Spt6 in maintaining centromere identity through the potential targeting of the Psh1 E3 ligase that removes ectopically deposited histone H3 variant Cse4. Despite these findings, we know little about how Spt6 performs its chromatin-dependent activities. Thus, this proposal aims to elucidate the fundamental mechanisms by which Spt6 contributes to the maintenance of chromatin structure in the coding and regulatory regions of the genome - thereby contributing to the biology of Spt6 and to the mechanisms by which chromatin domains are established and maintained. To accomplish this goal, we will address the following key questions: 1) How is Spt6 regulated through its interactions with RNAPII and by post-translational modifications that occur on this protein? 2) Why is Spt6 cell cycle regulated, and what role does it play in S phase? 3) Does Spt6 function outside of its canonical role in transcriptional regulation to regulate other aspects of chromatin biology, in particular centromere identity? Given the conservation of Spt6 across evolution, our studies will significantly impact our understanding of the mechanisms that underlie transcriptional elongation and the maintenance of chromatin integrity that govern genome integrity. These studies will also be relevant to our understanding of Spt6 in human development and disease.