Quality Control Mechanisms in Protein Synthesis

项目摘要 这个研究项目的目标是获得对翻译的更深层次的机械洞察，翻译是一种保守的细菌系统 翻译质量控制、定向蛋白分解和持续的信使核糖核酸衰变。我们建议的研究的基本前提是 SmpB-tmRNA介导的翻译过程解决了由不间断mRNAs引起的所有问题，包括 挽救和回收停滞不前的核糖体，对潜在有毒的新生多肽进行蛋白质分解，以及 致病缺陷基因的选择性衰变。我们认为tmna挽救的核糖体作为招募的中心。 建立专门的救援因素，启动相互关联的打捞路径。因此，在未来五年，我们将 阐述翻译过程的两个独立方面：(1)接头引导的tmna标记蛋白的蛋白分解 (2)tmRNA促进的持续mRNA衰变。在Aim I中，我们将调查翻译机制是否起到了 通过招募AAA+ClpXP蛋白酶系统来翻译核糖体来启动引导蛋白降解的平台。这个 我们研究的主要目的是研究一种新的底物识别机制，使ClpXP蛋白酶能够通过其 特异性增强因子SspB，在核糖体上的生物发生部位捕获标记的蛋白质。详细的知识 通过这一新途径捕获特定底物的研究将为AAA+酶是如何 旨在确定细胞的位置以及蛋白酶如何有助于细胞在不利条件下的健康和存活。在……里面 目的研究tmRNAs介导的核糖体拯救系统与选择性捕获和释放的关系。 RNase R对有缺陷的mRNAs的衰变我们希望阐明RNase R被招募到翻译中的机制 并确定其在被拯救的核糖体上的确切结合部位和相互作用伙伴。我们将探索这种可能性 核糖体成分的独特修饰产生了在招募RNaseR中起关键作用的特殊核糖体 TmRNA拯救的核糖体。最近的研究提供了令人信服的证据证明，音译 Process和ClpXP和Lon蛋白水解酶是几种致病菌不同调控途径的关键参与者，以及 因此都是发病所必需的。这个项目中提出的遗传、生化和结构研究提供了 获得对翻译流程的重要新见解并确定未来新目标的独特机会 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.