CHROMATIN AND EPIGENETIC INHERITANCE

DNA和组蛋白的共价修饰对于调节基因表达是重要的。 在这里，我提出解决两个基本的，未回答的问题，染色质 修饰：i）在发育过程中如何建立染色质状态的变化;以及ii） 一旦建立，染色质修饰是如何在未来的细胞中稳定保存的？ 部门？首先，我们将集中我们的分析，了解如何非编码RNA存在， 建立了雌性哺乳动物细胞中X染色体的沉默。在启动X- 在失活过程中，Xist RNA顺式扩散，包裹将变得失活的X染色体， 介导沉默，并触发染色质修饰的顺序积累。如何 Xist RNA启动沉默仍然未知。一种深入了解 Xist是识别相互作用的蛋白质。我们已经得到的结果表明，Xist是部分 一个大的蛋白质复合体。因此，在目标1中，我们建议使用经典和非经典的方法。 常规纯化策略来鉴定Xist相互作用蛋白。来鉴定蛋白质 为了维持非活性X的沉默，我们将在 目标2，它基于失活X的再活化。我们希望能找到相关的蛋白质 沉默X染色体状态的表观遗传。细胞周期构成了 表观遗传的一个特别具有挑战性的问题，因为组蛋白修饰必须 当DNA链在S期复制时，因此，一个主要问题是， 染色质修饰是如何通过细胞分裂传递的，如果它们确实是 足够作为表观遗传信息的载体。令人惊讶的是，我们发现组蛋白 在整个细胞周期中，对失活X的修饰不会累积。在目标3中，我们 对组蛋白修饰的细胞周期调控进行了深入研究。

Covalent modifications of both DNA and histones are important for regulating gene expression. Here, I propose to address two fundamental, unanswered questions about chromatin modifications: i) how are changes in chromatin states established during development; and ii) once established, how are chromatin modifications stably preserved through future cell divisions? Initially, we will focus our analysis on understanding how the noncoding RNA Xist establishes silencing of the X chromosome in female mammalian cells. During initiation of X- inactivation, Xist RNA spreads in cis to coat the X chromosome that will become inactive, mediates silencing, and triggers the sequential accumulation of chromatin modifications. How Xist RNA initiates silencing remains unknown. One approach to gain insight into the function of Xist is to identify interacting proteins. We have obtained results demonstrating that Xist is part of a large protein complex. In Aim 1, we therefore propose to use classical and non- conventional purification strategies to identify Xist -interacting proteins. To identify proteins necessary for maintaining the silence of the inactive X, we will perform an RNAi based screen in Aim 2, which is based on the reactivation of the inactive X. We expect to find proteins involved in the epigenetic inheritance of the silent X chromosome state. The cell cycle poses a particularly challenging problem for epigenetic inheritance since histone modifications have to be maintained when DNA strands are duplicated during S phase. A major question therefore is, how chromatin modifications are transmitted through cell divisions, and if they are indeed sufficient as carriers of the epigenetic information. Surprisingly, we have found that histone modifications on the inactive X do not accumulate throughout the cell cycle. In Aim 3, we will extent studies on the cell cycle regulation of histone modifications.