Mechanism of Eukaryotic Translation Termination

翻译终止是蛋白质合成的最后阶段。它至少包括两个基本功能，停止 密码子识别和多肽链释放。在真核生物中，I类释放因子eRF1 识别三个终止密码子(UAA、UAG和UGA)中的每一个，并调节新生密码子的释放 多肽链。第二类释放因子eRF3在依赖GTP的 举止。这个项目的长期目标是更好地理解翻译终止的过程，因此 旨在抑制导致疾病的过早停止突变的治疗策略可以是 发展起来的。 ERF1蛋白包含三个不同的结构域。对结构和遗传数据的考虑导致了 结构域1介导终止密码子识别；结构域2与肽基转移酶相互作用 核糖体的中心促进多肽链的释放；结构域3介导相互作用 ERF1和eRF3。相互竞争的模型认为，领域1中的TASNIKS主题或YCF主题是 对终止密码子识别至关重要。这项提案的第一个目标是确定eRF1结构域1的关键残基 参与终止密码子识别，以测试这些竞争模型的相对优点。 酵母SUP45基因编码eRF1。我们最近发现，SUP45基因的半衰期是 受制于终止程序的效率。这种机制导致eRF1的增加 当终止受到损害时的蛋白质水平。这项提案的第二个目标将测试这一模型和 探索这种新的调控机制是如何控制SUP45 mRNA和eRF1蛋白水平的。 我们最近发现，以前未描述的蛋白Tpa1p会影响翻译效率 酵母细胞中的末端、信使核糖核酸聚(A)尾长和信使核糖核酸半衰期。这导致我们提出了一个模型， Tpa1p将翻译终止与细胞内mRNAs的去烯化结合在一起。这样做的第三个目的 提案将测试此模型的各个方面，以便我们可以更好地了解 翻译终止与信使核糖核酸稳定性。

Translation termination is the final stage of protein synthesis. It includes at least two essential functions, stop codon recognition and polypeptide chain release. In eukaryotic organisms, the class I release factor eRF1 recognizes each of the three termination codons (UAA, UAG, and UGA) and mediates release of the nascent polypeptide chain. The class II release factor eRF3 assists the termination process in a GTP-dependent manner. The long-term goal of this project is to better understand the process of translation termination so therapeutic strategies aimed at the suppression of disease-causing premature stop mutations can be developed. The eRF1 protein contains three discrete domains. A consideration of structural and genetic data led to the proposal that domain 1 mediates stop codon recognition; domain 2 interacts with the peptidyl transferase center of the ribosome to facilitate polypeptide chain release; and domain 3 mediates the interaction between eRF1 with eRF3. Competing models argue that either the TASNIKS motif or the YCF motif in domain 1 is critical for stop codon recognition. The first aim of this proposal will identify key residues of eRF1 domain 1 involved in stop codon recognition to test the relative merits of these competing models. The yeast SUP45 gene encodes eRF1. We recently discovered that the half-life of the SUP45 mRNA is regulated by the efficiency of the termination process. This mechanism leads to an increase in the eRF1 protein level when termination is compromised. The second aim of this proposal will test this model and explore how this novel regulatory mechanism controls SUP45 mRNA and eRF1 protein levels. We recently found that the previously uncharacterized protein Tpa1p influences the efficiency of translation termination, mRNA poly(A) tail length, and mRNA half-life in yeast cells. This led us to propose a model in which Tpa1p couples translation termination to the deadenylation of cellular mRNAs. The third aim of this proposal will test various aspects of this model so we can better understand the important interplay between translation termination and mRNA stability.