Molecular mechanisms of eukaryotic translational control

摘要： 细胞中合成的每种蛋白质的水平既取决于可获得的信使核糖核酸的量，也取决于可用信使核糖核酸的量。 启动该信使核糖核酸翻译的核糖体数量。真核翻译起始因子 (EIF)可以重新编程哪些mRNAs可用并进行翻译，以产生不同水平的 编码蛋白质以响应离散的细胞信号。在真菌物种中，翻译控制发挥作用 在宿主逃避和其他致病机制中以及在哺乳动物物种中， EIF水平的改变和修饰会影响癌症的进展和其他疾病状态。一个 许多蛋白质因子刺激翻译，包括eIF4因子(4A、B、E、G和H)， 启动mRNA5‘端和核糖体的小亚基，以在开始前促进事件的发生 场地识别。大量数据支持RNA解旋酶4A和辅因子4B和4G在 解开5‘UTRs以促进结构化mRNAs的翻译。然而，依赖于 基于4B的翻译活动与严重依赖4G的活动不同，尽管这两个因素 推进4A活动。此外，与前列腺癌4A和4G形成鲜明对比的是，增加的 4B可改善侵袭性癌症患者的生存率，初步数据直接与4B有关 在抗小鼠乳腺癌转移中的作用。了解4B如何调解翻译 特定的转录本可能对了解和预测转移表型很重要。 最后，已知eIF4因子的翻译后修饰在 哺乳动物，而放松管制在疾病状态下很常见。然而，目前尚不清楚如何修改 EIF4因子调节真菌物种中的翻译以及这如何影响特定基因的表达 信使核糖核酸。这份提案接受了这些挑战，投入了多年的经验来表征 酵母翻译启动的机制和强大的体外、遗传和基因组武器库- 宽阔的工具。为了更好地了解核糖体如何选择mRNAs进行翻译， 这项工作的目标是了解4B如何实现翻译与压制 酵母中特定的信使核糖核酸库。将追求三个目标：目标1.确定4F和4B如何 相互作用影响4B高依赖和低依赖mRNAs的翻译。目的2.阐明酵母4B- RNA结合首选项。目标3.了解4F和4F的翻译后修饰(PTM) 4B Impact 4B特异性mRNA调控。该提案将使用eIF4B作为模型，以确定核心 翻译起始因子调节特定信使核糖核酸库和意志的翻译与抑制 阐明了4B的强劲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.