Transcriptional Regulation by Epigenetic Factors

项目总结： 细胞记忆在分化和疾病过程中起着关键作用。它依赖于表观遗传 这对于通过细胞生成来传播基因表达程序至关重要，在很大程度上是通过 维持子代细胞染色质结构。DNA复制是人类免疫缺陷的主要障碍 染色质结构的保守性。在复制过程中，大多数蛋白质被认为是从 DNA少数分子可能仍然与DNA相关，从而标记DNA调控元件 染色质未来成熟为开放的或紧密的构象。这些表观遗传学的同一性 马克是未知的。最好的候选者被认为是修饰的组蛋白，因为它们是假设的 在新生的DNA上从双亲转移到子代。然而，直到最近，还有 既没有实验方法直接检查表观遗传标记的性质，也没有 复制后染色体蛋白向DNA募集的顺序和时间。同样，我们知道 关于DNA复制后转录如何以及何时恢复的信息很少。 我们开发了几种新的实验方法来解决这些关键的表观遗传学 问题，并发现染色质的结构并没有像目前所说的那样严重破坏。 在新生DNA上发现了RNA聚合酶II和相关的一般转录和延伸因子 就在复制之后。此外，即使是未成熟的核糖核酸也在接近新生DNA的地方被发现。 这表明RNA POL II-RNA复合体能够在DNA复制中幸存下来。我们还发现， DNA复制后，转录恢复得相对较快。基于我们发布的和初步的 结果，我们建议测试一个新的表观遗传学概念，该概念认为一旦转录建立， 大多数转录装置可能通过复制与DNA联系在一起，从而起到 活性基因的表观遗传标记。然而，这种可能性与传统模式相冲突。 这表明转录和复制复合体沿着DNA移动，因为这将导致碰撞 这些蛋白质复合体。为了解决这一矛盾，我们将检验以下假设： 通过复制的转录机制可以被解决，如果转录和复制发生在 固定核亚区、转录和复制工厂，以及DNA被卷绕 通过这些蛋白质工厂。这些实验的结果将大大有助于我们的 对表观遗传过程的理解，并可能对开发新的 在许多生物和药物发现领域的方法。

Project Summary: Cell memory plays a key role during differentiation and disease. It relies on epigenetic inheritance that is essential to propagate gene expression program through cell generation, in large part through maintaining the structure of chromatin in daughter cell. DNA replication is the major obstacle in conservation of chromatin structure. During replication, most proteins are thought to dissociate from DNA. A few molecules may remain associated with DNA, thus marking DNA regulatory elements for future maturation of chromatin into an open or compact conformation. The identity of these epigenetic marks is unknown. The best candidates are thought to be modified histones because they are assumed to transfer from the parental to daughter nucleosomes on nascent DNA. However, until recently, there were no experimental approaches to directly examine neither the nature of epigenetic marks, nor the order and timing of recruitment of chromosomal proteins to DNA following replication. Similarly, we know very little about how and when transcription resumes after DNA replication. We developed several new experimental approaches that allow addressing these key epigenetic issues, and found that the structure of chromatin is not as severely disrupted as is currently suggested. RNA Polymerase II and related general transcription and elongation factors are found on nascent DNA just after replication. Moreover, even immature RNAs are found in the proximity to nascent DNA suggesting that the RNA Pol II – RNA complex is able to survive DNA replication. We also found that transcription resumes relatively quickly after DNA replication. Based on our published and preliminary results, we propose to test a new epigenetic concept suggesting that once transcription is established, most of the transcriptional apparatus may be associated with DNA through replication, thus serving as an epigenetic mark for active genes. This possibility, however, conflicts with the conventional model suggesting that transcription and replication complexes travel along DNA, since this will lead to collisions of these protein complexes. To resolve this contradiction, we will test the hypothesis that the stability of the transcriptional machinery through replication can be resolved if transcription and replication occur in the stationary nuclear sub-domains, transcription and replication factories, and that DNA is reeled through these protein factories. The results of these experiments will greatly contribute to our understanding of the epigenetic processes, and may have a major impact on developing new approaches in many biological and drug discovery fields.