Assembly Localiztion and Function of the U3 snRNP

描述(申请人提供)：大量的细胞代谢致力于产生核糖体，核糖体是蛋白质合成的大型核糖核蛋白工厂，负责将mRNAs翻译成蛋白质。核糖体是在核仁中合成的，经过一系列的核内和核外溶解反应，将前-rRNA加工成18S、5.8S和25S rRNA。我的实验室最近纯化并鉴定了一种新的大RNP，SSU(小亚基)过程组，这是18S前rRNA加工所必需的。虽然我们的工作已经发现了30+的SSU加工体蛋白质，但我们假设可能还有其他重要的成分，包括RNA解旋酶和内切酶，与SSU加工组一起发挥成熟18S rRNA的功能。此外，关于SSU加工体在Pre-rRNA上的组装以及它与Pre-rRNA转录的关系，人们知之甚少。我们的长期目标是了解核糖体生物发生所必需的前rRNA加工、RNA折叠和核糖体组装步骤。这项应用的目的是揭示小核糖体亚单位(SSU)生物发生的不同方面，包括动态性质。中心假设是，在188rRNA前的SSU加工组的形成是SSU生物发生的关键部分。我们的工作具有重要意义，因为SSU过程对所有真核细胞中的基因表达至关重要，从而对细胞生长至关重要。在特定的目标1中，我们将检验这样的假设，即DExD/H盒RNA解旋酶保守基序的突变可以用来更准确地确定它们在SSU生物发生中的功能。在目标2中，我们将进一步研究前rRNA转录和由SSU过程组组件介导的加工之间的联系。在目标3中，我们将检验ORF YOR004w和YDR339c编码的蛋白质编码18S前rRNA加工所需的内切酶的假设。在目标4中，我们将检验这一假设，即还有其他非必需基因编码参与前18S rRNA核糖体生物发生的蛋白质。

DESCRIPTION (provided by applicant): A tremendous amount of cellular metabolism is dedicated to producing ribosomes, the large ribonucleoprotein factories of protein synthesis responsible for translating mRNAs into proteins. Ribosomes are synthesized in the nucleolus following a series of endonucleolytic and exonucleolytic reactions that process the pre-rRNA to the 18S, 5.8S and 25S rRNAs. My laboratory has recently purified and characterized a new large RNP, the SSU (small subunit) processome, which is required for pre-18S rRNA processing. While our work has uncovered 30+ of the SSU processome proteins, we hypothesize that there may be other important components, including RNA helicases and endonucleases, that function with the SSU processome to mature the 18S rRNA. In addition, very little is known about the assembly of the SSU processome on the pre-rRNA and how it is related to pre-rRNA transcription. Our long-term goal is to understand the pre-rRNA processing, RNA folding and ribosome assembly steps essential to ribosome biogenesis. The objective of this application is to uncover different aspects, including the dynamic nature, of small ribosomal subunit (SSU) biogenesis. The central hypothesis is that formation of the SSU processome on the pre-188 rRNA is a critical part of SSU biogenesis. Our work is significant because the SSU processome is vital to gene expression, and therefore cell growth, in all eukaryotic cells. In Specific Aim 1, we will test the hypothesis that mutations in conserved motifs in DExD/H box RNA helicases can be used to more precisely define their function in SSU biogenesis. In Aim 2, we will further investigate the link between pre-rRNA transcription and processing mediated by the SSU processome components. In Aim 3, we will test the hypothesis that the proteins encoded by ORFS YOR004w and YDR339c encode endonucleases required for pre-18S rRNA processing. In Aim 4, we will test the hypothesis that there are other non-essential genes encoding proteins involved in pre-18S rRNA ribosome biogenesis.