The role of UFMylation in ribosome quality control at the ER

项目摘要 核糖体是破译基因组的大分子机器。质量控制 因此，确保这一过程的保真度的机制至关重要 以及生物体的生存能力。核糖体以不同的速度移动，减慢甚至暂停 促进细胞器靶向、结构域折叠和共翻译组装，但长期停滞不前 对细胞有害，因为它们会耗尽功能核糖体并产生剧毒 被截断的新生链条。发生在内质网(ER)核糖体上的停滞是均匀的 更具破坏性，因为它们还阻挡了所有人分泌的转座子 而膜蛋白必须在进入分泌途径的过程中转运。核糖体质量 控制(RQC)是一个保守和必要的过程，通过以下方式拯救停滞的60S亚基 提取阻碍新生链条，并用UPS将其降解。尽管有巨大的 过去十年在定义胞质核糖体RQC方面的进展，RQC是如何运作的 ER停滞的核糖体几乎完全没有被研究过。最近我的实验室发现 UFM化-UFM1，一种类似泛素的小蛋白连接到UFM1的过程 核糖体--在RQC适应蛋白质的过程中起着核心和重要的作用 在急诊室合成的。本提案中描述的三个具体目标寻求建立在 由我们提供的大量初步数据提供的基础来定义 阻碍停滞在内质网转运子上的核糖体的新生链条被提取并 降级了。在目标1中，我们将对RQC机制进行系统的剖析，以定义 已知的RQC在解决急诊室停滞的核糖体方面所起的作用。在目标2中，我们将定义 核糖体UFM化与RQC的相互作用及UFMylated阅读器的识别 急诊室的核糖体。在目标3中，我们将确定UF肌化核糖体的结构和 连接UFM1和核糖体的E3连接酶。

Project Summary Ribosomes are macromolecular machines that decode the genome. Quality control mechanisms that ensure the fidelity of this process are thus of paramount importance cellular and organismal viability. Ribosomes move at variable rates, slowing down or even pausing to facilitate organelle targeting, domain folding and co-translational assembly, but prolonged stalls are deleterious to cells because they can deplete functional ribosomes and produce highly toxic truncated nascent chains. Stalls that occur on endoplasmic reticulum (ER) ribosomes are even more damaging because they additionally obstruct the translocons through which all secreted and membrane proteins must transit en route to the secretory pathway. Ribosome quality control (RQC) is a conserved and essential process that rescues stalled 60S subunits by extracting the obstructing nascent chain and degrading it by the UPS. Despite immense progress in the past decade in defining RQC for cytosolic ribosome, the how RQC operates for ER-stalled ribosomes is almost completely uninvestigated. Recently my lab discovered that UFMylation – the process by which UFM1, a small ubiquitin-like protein is conjugated to ribosomes — plays a central and essential role specifically in adapting RQC to proteins synthesized at the ER. The three specific aims described in this proposal seek to build on the foundation provided by our extensive preliminary data to define the mechanism by which nascent chains that obstruct ribosomes that stall on ER translocons are extracted and degraded. In aim 1 we will conduct a systematic dissection of the RQC machinery to define the role of known RQC required to resolve stalled ribosomes at the ER. In aim 2 we will define the interplay between ribosome UFMylation and RQC and dentify the readers of UFMylated ribosomes at the ER. In aim 3 we will determine the structure of UFMyulated ribosomes and the E3 ligase that conjugates UFM1 to the ribosome.