Quality Control Mechanisms in Protein Synthesis

项目摘要 该研究项目的目标是获得更深入的反式翻译机制见解，这是一种保守的细菌系统， 翻译质量控制、定向蛋白水解和不间断的mRNA衰变。我们研究的基本前提是 SmpB-tmRNA介导的反式翻译过程解决了由不间断mRNA引起的所有问题，包括 挽救和回收无效停滞的核糖体，蛋白水解潜在毒性的新生多肽， 导致缺陷的mRNA的选择性衰减。我们认为，tRNA拯救的核糖体作为一个枢纽招聘 专门的抢救因素和启动相互联系的抢救途径。因此，在未来五年内，我们将 阐述了反式翻译过程的两个独立方面：（1）衔接子引导的tmRNA标记蛋白质的蛋白水解 （2）tRNA促进的mRNA不间断降解。在目的一，我们将调查是否翻译机器作为一个 用于通过募集AAA+ ClpXP蛋白酶系统翻译核糖体来启动引导的蛋白水解的平台。的 我们研究的主要目的是研究一种新的底物识别机制，使ClpXP蛋白酶，通过其 特异性增强因子SspB，以在核糖体上的生物发生位点捕获标记蛋白。的详细知识 通过这种新途径捕获特定底物的方法将为AAA+酶如何被捕获提供重要的新线索。 旨在定义细胞位置以及蛋白酶如何在不利条件下促进细胞适应性和存活。在 目的二，我们将研究tRNA介导的核糖体拯救系统和选择性捕获之间的联系， RNA酶R降解缺陷mRNA。我们希望阐明核糖核酸酶R被招募到翻译的机制， 机器和定义其确切的结合位点和相互作用的合作伙伴拯救核糖体。我们会研究 核糖体成分的独特修饰产生了专门的核糖体，这些核糖体在募集RNase R中起着关键作用， 转移到tRNA拯救的核糖体。最近的研究提供了令人信服的证据表明， 过程和ClpXP和Lon蛋白酶是几种病原菌中各种调节途径的关键参与者， 因此是发病所必需的。该项目中提出的遗传、生物化学和结构研究提供了 这是一个独特的机会，可以获得对翻译过程的重要新见解，并确定未来的新目标。 开发新的抗生素。

Project Summary The goal of this research project is to gain deeper mechanistic insights into trans-translation, a conserved bacterial system for translation quality control, directed proteolysis, and nonstop mRNA decay. The fundamental premise of our proposed studies is that the SmpB-tmRNA mediated trans-translation process solves all of problems caused by nonstop mRNAs, including rescue and recycling of unproductively stalled ribosomes, proteolysis of the potentially toxic nascent polypeptides, and selective decay of the causative defect mRNA. We propose that the tmRNA-rescued ribosome serves as a hub for recruitment of specialized rescue factors and initiation of interconnected salvage pathways. Therefore, over the next five years we will address two independent aspects of the trans-translation process: (1) adaptor guided proteolysis of tmRNA tagged proteins and (2) tmRNA-facilitated nonstop mRNA decay. In Aim I, we will investigate whether the translation machinery serves as a platform for initiating guided proteolysis by recruiting the AAA+ ClpXP protease system to translating ribosomes. The primary aim of our studies is to investigate a novel substrate recognition mechanism that enables the ClpXP protease, via its specific-enhancing factor SspB, to capture marked proteins at their site of biogenesis on the ribosome. A detailed knowledge of how specific substrate are captured via this novel pathway will shed significant new light on how AAA+ enzymes are directed to define cellular locations and how proteases contribute to cellular fitness and survival under adverse conditions. In Aim II, we will investigate the link between the tmRNA-mediated ribosome rescue system and the selective capture and decay of defective mRNAs by RNase R. We wish to elucidate the mechanism by which RNase R is recruited to the translation machinery and define its exact binding site and interacting partners on the rescued ribosome. We will explore the possibility that a unique modification of ribosomal components creates specialized ribosomes that play a key role in recruiting RNase R to tmRNA-rescued ribosomes. Recent studies have provided compelling evidence to demonstrate that the trans-translation process and ClpXP and Lon proteases are key participants in various regulatory pathways in several pathogenic bacteria, and therefore are required for pathogenesis. The genetic, biochemical, and structural studies proposed in this project offer the unique opportunity to gain significant new insights into the trans-translation process and identify new targets for future development of new antibiotics.