Mechanisms of Circadian Clock Control of mRNA Translation

摘要 生物钟对人类健康和药物新陈代谢至关重要，它调节有节奏的蛋白质生产。 从而影响细胞功能和新陈代谢。产生了许多蛋白质，它们的水平表现出强烈的昼夜节律。 来自没有节奏的mRNA。使用真核生物粗糙脉孢菌的模型，我们发现多达一半的 这种对蛋白质水平的昼夜节律调节是通过时钟控制保守的 翻译起始(eIF2α)，以及翻译核糖体的蛋白质组成。我们还制作了令人惊讶的 对生物钟控制核糖体通过正常停顿读取的概率的观察 密码子产生具有羧基末端延伸和潜在新功能的蛋白质。另外，我们发现， 生物钟调节tRNA合成酶的水平，tRNA合成酶向tRNA充电，使其含有适当的氨基酸 翻译，因此对准确的蛋白质合成至关重要。在接下来的5年里，我们将利用这些 测试这一令人兴奋的假设的发现，即生物钟控制翻译保真度和翻译保真度的每日变化 因此，蛋白质的多样性超出了基因组的编码范围。我们将确定核糖体的时钟控制 韵律终止密码子的组成是必需的，以及需要哪些特定的核糖体蛋白 通读。此外，我们还将测试协同伴侣Zuotin与核糖体结合的昼夜节律控制 调节蛋白质折叠的日常节律。我们将确定昼夜节律对甲硫酰-tRNA的影响 合成酶(MetRs)水平以及使MetRS磷酸化的激酶活性的节律，在三种不同的 MetRS调控通路。这些包括通过充电启动子蛋氨酰tRNA来启动翻译， 延伸物甲硫酰tRNA的荷电和甲硫氨酸的错误掺入 蛋白质合成通过非同源tRNA的错误充电。这项工作将对我们的 了解细胞在一天中的不同时间有何不同，以及蛋白质组如何可以 比人们从基因组序列中预测的要多样化。

Summary The circadian clock, critical to human health and drug metabolism, regulates rhythmic protein production and thus cell function and metabolism. Many proteins whose levels show robust circadian rhythms are produced from mRNAs that are not rhythmic. Using the model eukaryote Neurospora crassa, we found that up to half of this circadian regulation of protein levels is through clock control of the activities of a conserved regulator of translation initiation (eIF2α), and the protein composition of translating ribosomes. We also made the surprising observation that the circadian clock controls the probability that ribosomes will read through the normal stop codon to produce proteins with carboxy-terminal extensions and potentially new functions. In addition, we found that the clock regulates the levels of tRNA synthetases that charge tRNAs with the appropriate amino acids for translation, and thus are critical for accurate protein synthesis. Over the next 5 years, we will capitalize on these findings to test the exciting hypothesis that the circadian clock controls daily changes in translation fidelity and thus protein diversity beyond what is encoded for in the genome. We will determine if clock control of ribosome composition is necessary, and which specific ribosomal proteins are required, for rhythmic stop codon readthrough. In addition, we will test if circadian clock control of binding of the co-chaperone Zuotin to ribosomes regulates daily rhythms in protein folding. We will determine the impact of circadian rhythms in methionyl-tRNA synthetase (MetRS) levels, and rhythms in the activities of kinases that phosphorylate MetRS, on three different MetRS regulatory pathways. These include translation initiation through charging of the initiator methionyl tRNA, translation elongation through charging of elongator methionyl tRNA, and misincorporation of methionine during protein synthesis through the mischarging of non-cognate tRNA. This work will significantly impact our understanding of both how a cell is different at different times of the day, and how the proteome can be more diverse than what one would predict from the genome sequence.