mRNA Template-free Protein Elongation: a New Paradigm for Quality Control at the Ribosome

项目摘要 这项研究旨在增加有关细胞如何处理蛋白质缺陷的基础知识。 以及这些失败如何导致疾病。核糖体的蛋白质合成会异常地停止 （“停滞”）的原因有很多，包括错误的mRNA，翻译组件的可用性不足， 基因错误处理这些失败是至关重要的，因为对停滞的蛋白质合成的异常反应已经被发现。 会导致神经退化为了科普这种负担，真核细胞采用一种称为 核糖体相关质量控制（RQC），检测停滞的核糖体并促进核糖体的降解。 核糖体先前合成的蛋白质（“停滞的新生链”）。作为RQC的一部分，我们 发现蛋白质Rqc2劫持核糖体附加羧基末端丙氨酸和苏氨酸， 在一些实施方案中，CAT尾（“CAT尾”）被引入停滞的新生链。CAT尾巴通过标记停滞的新生链使细胞受益， 降解奇怪的是，CAT尾巴也可以通过形成损害细胞活力的有毒聚集物来伤害细胞。 猫尾巴如何拥有这些看似矛盾的行为（有益与有毒）仍不清楚。这 一项研究计划将利用生物化学、细胞生物学和基因组学来填补这一知识空白。 研究方法：1）细胞如何合成CAT尾巴，2）细胞如何降解CAT尾巴，3）CAT尾巴如何 在后生动物中表现出来。这项研究将阐明细胞用来保护自己免受 失败的蛋白质合成，并揭示其失调的原因和后果。

Project Summary This research effort seeks to increase fundamental knowledge about how cells handle failures in protein synthesis and how these failures can lead to disease. Protein synthesis by the ribosome can abnormally halt (“stall”) for numerous reasons, including faulty mRNA, insufficient availability of translation components, and genetic errors. Handling these failures is critical, as abnormal responses to stalled protein synthesis have been demonstrated to cause neurodegeneration. To cope with this burden, eukaryotic cells employ a process called Ribosome-associated Quality Control (RQC) that detects stalled ribosomes and promotes degradation of the protein that the ribosome was previously synthesizing (the “stalled nascent chain”). As part of RQC, we discovered that the protein Rqc2 hijacks the ribosome to append Carboxy-terminal Alanine and Threonine residues (“CAT tails”) to the stalled nascent chain. CAT tails benefit cells by marking stalled nascent chains for degradation. Curiously, CAT tails can also harm cells by forming toxic aggregates that impair cellular viability. How CAT tails possess these seemingly contradictory behaviors (beneficial vs. toxic) remains unclear. This research program will address this knowledge gap by using biochemical, cell biological, and genomic approaches to study: 1) how cells synthesize CAT tails , 2) how cells degrade CAT tails, and 3) how CAT tails behave in metazoans. This study will elucidate a fundamental mechanism cells use to protect themselves from failed protein synthesis and uncover the causes and consequences of its misregulation.