Molecular mechanisms of eukaryotic translational control

总结： 细胞中合成的每种蛋白质的水平取决于可用的mRNA的量， 启动mRNA翻译的核糖体数量。真核翻译起始因子 （eIF）可以重新编程哪些mRNA是可用的，并翻译以产生不同水平的mRNA。 编码蛋白质来响应离散的细胞信号。在真菌物种中，翻译控制起着 在宿主逃避和其他发病机制中的重要作用，以及在哺乳动物物种中， eIF水平的改变和修饰影响癌症进展和其他疾病状态。一 许多蛋白质因子刺激翻译，包括eIF 4因子（4A、B、E、G和H）， 接合mRNA的5'帽和核糖体的小亚基，以在开始之前促进事件 网站识别充足的数据支持RNA解旋酶4A和辅因子4 B和4G在 解旋5'UTR以促进结构化mRNA的翻译。然而，依赖于 在4 B上进行翻译的活动与严重依赖4G的活动不同，尽管这两个因素 开展4A活动。此外，与促肿瘤性4A和4G形成鲜明对比的是， 4 B改善了侵袭性癌症患者的生存率，初步数据直接表明4 B 对抗小鼠乳腺癌的转移。理解4 B如何介导 特异性转录物对于理解和预测转移表型可能是重要的。 最后，已知eIF 4因子的翻译后修饰可调节细胞内的翻译。 在哺乳动物中，放松管制在疾病状态中很常见。然而，目前尚不清楚如何修改 eIF 4因子调节真菌物种中的翻译，以及这如何影响特异性 mRNA库。该提案应对这些挑战，投入多年的经验， 酵母翻译起始的机制和强大的体外、遗传和基因组- 广泛的工具。为了更好地理解核糖体如何选择mRNA进行翻译， 这项工作的目的是了解4 B如何实现翻译与压抑的 酵母中的特定mRNA库。将追求三个目标：目标1。确定4F和4 B 相互作用影响4 B超依赖性和低依赖性mRNA的翻译。目标二。阐明酵母4 B- RNA结合偏好。目标3.了解4F和4F的翻译后修饰（PTM） 4 B影响4 B特异性mRNA控制。该提案将使用eIF 4 B作为模型，以确定核心 翻译起始因子调节特定mRNA库的翻译与阻遏， 揭示了4 B的强大活性如何对抗转移表型。

SUMMARY: The level of each protein synthesized in a cell results from both the amount of mRNA available, and the number of ribosomes that initiate translation of that mRNA. Eukaryotic translation initiation factors (eIFs) can reprogram which mRNAs are available and translated to produce different levels of the encoded proteins in response to discrete cellular signals. In fungal species, translational control plays important roles in host evasion and other pathogenesis mechanisms, and in mammalian species, altered levels and modifications of eIFs influence cancer progression and other disease states. A number of protein factors stimulate translation, including the eIF4 factors (4A, B, E, G, and H) that engage the 5’ cap of mRNA and the small subunit of the ribosome, to promote events prior to start site recognition. Ample data support roles of the RNA helicase 4A and cofactors 4B and 4G in unwinding 5’ UTRs to promote translation of structured mRNAs. However, the mRNAs that depend on 4B activity for translation are distinct from those that rely heavily on 4G, even though both factors promote 4A activity. Moreover, in striking contrast to protumorigenic 4A and 4G, increased levels of 4B improved survival of patients with aggressive cancers, and preliminary data directly implicated 4B in opposing metastasis of murine breast cancers. Understanding how 4B mediates translation of specific transcripts could be important for understanding and predicting metastatic phenotypes. Finally, posttranslational modifications of the eIF4 factors are known to modulate translation in mammals, and deregulation is common in disease states. However, it is unclear how modifications of the eIF4 factors regulate translation in fungal species and how this affects expression of specific mRNA pools. This proposal takes on these challenges, investing years of experience characterizing the mechanics of yeast translation initiation and a powerful arsenal of in vitro, genetic, and genome- wide tools. In order to better understand how mRNAs are selected by ribosomes for translation, the objective of this work is to understand how 4B achieves translation versus repression of specific mRNA pools in yeast. Three aims will be pursued: Aim 1. Determine how 4F and 4B interactions affect translation of 4B hyper and hypo-dependent mRNAs. Aim 2. Elucidate yeast 4B- RNA binding preferences. Aim 3. Understand how posttranslational modifications (PTMs) of 4F and 4B impact 4B-specific mRNA control. This proposal will use eIF4B as a model to determine how core translation initiation factors modulate translation versus repression of specific mRNA pools and will shed light on how robust activity of 4B opposes the metastatic phenotype.