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eRF 1 识别三种终止密码子（UAA、UAG和UGA）中的每一种，并介导新生的 多肽链II类释放因子eRF 3在GTP依赖性的细胞内协助终止过程。 方式这个项目的长期目标是更好地理解翻译终止的过程， 旨在抑制引起疾病的过早终止突变的治疗策略可以 开发 eRF 1蛋白包含三个离散结构域。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 结构域3介导核糖体的中心以促进多肽链释放; eRF 1和eRF 3。竞争性模型认为，结构域1中的TASNIKS基序或YCF基序是 对于终止密码子识别至关重要。本提案的第一个目的是鉴定eRF 1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SUP 45基因编码eRF 1。我们最近发现SUP 45 mRNA的半衰期是 由终止过程的效率来调节。这种机制导致eRF 1增加， 蛋白质水平时，终止受到损害。本提案的第二个目的是检验这一模式， 探索这种新的调节机制如何控制SUP 45 mRNA和eRF 1蛋白水平。 我们最近发现，以前未表征的蛋白Tpa 1 p影响翻译效率 终止、mRNA聚（A）尾长和mRNA在酵母细胞中的半衰期。这使我们提出了一个模型， 其中Tpa 1 p将翻译终止与细胞mRNA的去腺苷化偶联。第三个目标是 该提案将测试该模型的各个方面，以便我们更好地了解 翻译终止和mRNA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.