Chromatin Modification and Pre-Messenger RNA Splicing

自2001年人类基因组序列公布以来，很明显，理解基因组的下一步是回答基本问题：“基因组中包含的信息如何表达，以及如何控制每个基因的正确表达？“基因组的两个特征使这成为一个特别有趣的问题。 首先，人类基因（以及其他真核生物的基因）被长段的非编码DNA序列打断。一旦DNA被细胞机器“读取”并转录成“信使RNA”（指导蛋白质合成的含有中间信息的遗传物质），这些长链的非编码RNA必须被去除，剩下的蛋白质编码区必须连接起来。 这个细胞过程，“前信使RNA剪接”，发生的精确度非常高，对正确的基因表达至关重要。基因组的第二个显著特征是DNA被包装在一个紧凑的蛋白质/DNA结构中，称为染色质。 为了使DNA序列被转录成信使RNA，染色质必须经历广泛的修饰，改变DNA包装并使DNA可访问。DNA可及性的这种变化在调节RNA合成中起着关键作用。 虽然参与基因表达的反应通常被独立研究，但最近的研究表明，RNA合成和剪接实际上是紧密协调的：剪接反应发生在RNA合成时。 因此，RNA合成反应可以影响剪接过程，而前mRNA剪接可以影响RNA合成。 鉴于前mRNA剪接和RNA合成之间的这些联系，人们可能会期望RNA合成机制导航染色质结构和合成信使RNA的能力与剪接机制协调去除内含子之间的联系。 本项目将利用生物化学和遗传学上易于处理的模式生物酿酒酵母，通过分析前体mRNA剪接机制与染色质修饰和染色质重组机制之间的协调，探索基因表达的基本机制。

Since the 2001 announcement of the sequence of the human genome, it has become evident that the next step toward understanding the genome is answering the fundamental questions: "How does the information contained within the genome get expressed, and how is the correct expression of each gene controlled?" Two features of the genome make this a particularly intriguing problem. First, human genes (and genes from other eukaryotic organisms) are interrupted by long stretches of non-coding DNA sequence. Once the DNA is "read" by the cellular machinery and transcribed to make "messenger RNA" (the intermediate information-containing genetic material that directs protein synthesis), these long stretches of non-coding RNA must be removed, and the remaining protein-coding regions must be joined. This cellular process, "pre-messenger RNA splicing," takes place with exquisite accuracy and is crucial for proper gene expression. The second notable feature of the genome is that the DNA is packaged in a compact protein/DNA structure called chromatin. In order for the DNA sequence to be transcribed to make messenger RNA, the chromatin must undergo extensive modification that alters the DNA packaging and makes the DNA accessible. This change in DNA accessibility plays a pivotal role in regulating RNA synthesis. While the reactions involved in gene expression have typically been studied independently, as isolated processes, recent studies have illustrated that RNA synthesis and splicing are, in fact, tightly coordinated: the splicing reaction occurs as the RNA is being synthesized. Consequently, the RNA synthesis reaction can affect the process of splicing, and pre-mRNA splicing can affect RNA synthesis. Given these connections between pre-mRNA splicing and RNA synthesis, one might expect connections between the RNA synthesis machinery's ability to navigate chromatin structure and synthesize messenger RNA, and the coordinated removal of introns by the splicing machinery. Using the biochemically and genetically tractable model organism, the yeast Saccharomyces cerevisiae, this project will explore the basic mechanisms underlying gene expression by analyzing the coordination between the pre-mRNA splicing machinery and the chromatin modifying and chromatin restructuring machineries.