Assembly Localiztion and Function of the U3 snRNP

描述（由申请人提供）：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mrna翻译成蛋白质。核糖体是在核仁中经过一系列核内溶和核外溶反应合成的，这些反应将前rrna加工成18S、5.8S和25S rrna。我的实验室最近纯化并表征了一种新的大型RNP，即SSU（小亚基）加工体，它是18s前rRNA加工所必需的。虽然我们的工作已经发现了30多个SSU加工体蛋白，但我们假设可能还有其他重要成分，包括RNA解旋酶和内切酶，与SSU加工体一起作用，使18S rRNA成熟。此外，对于SSU过程体在pre-rRNA上的组装及其与pre-rRNA转录的关系知之甚少。我们的长期目标是了解前rrna加工、RNA折叠和核糖体组装步骤对核糖体生物发生至关重要。这个应用程序的目的是揭示不同的方面，包括动态性质，小核糖体亚单位（SSU）生物发生。核心假设是，在pre-188 rRNA上形成SSU过程是SSU生物发生的关键部分。我们的工作意义重大，因为在所有真核细胞中，SSU过程对基因表达和细胞生长至关重要。在Specific Aim 1中，我们将验证DExD/H盒RNA解旋酶中保守基序的突变可以更精确地定义其在SSU生物发生中的功能。在Aim 2中，我们将进一步研究由SSU加工体成分介导的pre-rRNA转录和加工之间的联系。在Aim 3中，我们将验证ORFS YOR004w和YDR339c编码的蛋白质编码pre-18S rRNA加工所需的内切酶的假设。在Aim 4中，我们将验证存在其他非必需基因编码蛋白质参与18s前rRNA核糖体生物发生的假设。

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.