Circadian dynamics of cytoplasmic mRNA polyadenylation and deadenylation

 描述（由申请人提供）：整个身体的生物钟驱动数千个基因的节律表达，导致生物化学、生理学和行为的节律。在哺乳动物中，这些节律的破坏已被证明会导致严重的健康问题。除了对新陈代谢（包括肥胖和糖尿病）造成重大有害影响，增加某些类型癌症和心血管问题的风险外，最近的证据还表明生物钟与情感障碍，睡眠异常和重度抑郁症之间存在密切联系。尽管转录的昼夜节律控制已被广泛研究，但最近的数据表明，转录后控制（尽管了解得少得多）对于正常节律蛋白质表达谱也是至关重要的。一类员额 转录控制是mRNA poly（A）尾长度的调节，其影响稳定性和 mRNA的翻译调控。我们已经鉴定了数百种小鼠肝脏mRNA，它们在poly（A）尾的长度上表现出强大的昼夜节律。在许多情况下， 有节奏的尾长是有节奏的细胞质多腺苷酸化和去腺苷酸化节奏的结果，并且细胞质多腺苷酸化和去腺苷酸化机制的许多组分本身受昼夜节律控制。此外，节律性poly（A）尾与节律性蛋白表达密切相关。因此，生物钟调节许多mRNA的动态多聚腺苷酸化状态，这些mRNA可以独立于稳态水平的信息驱动有节奏的蛋白质表达。在这项提案中，我们将探索导致poly（A）尾节律的机制以及这些机制如何调节蛋白质的产生。在第一个具体的目标，我们将测试的假设，RNA结合蛋白CPEB2结合到特定的mRNA目标，并控制其多聚腺苷酸化状态，通过协调的相对活动的deadenylases和poly（A）聚合酶在一天中的时间依赖性的方式。在第二个具体目标中，将测试去腺苷酶Nocturnin负责去腺苷化的假设，并将确定Nocturnin的去腺苷化是否导致具有在夜间阶段调节的尾部的那些mRNA的衰变。在第三个目标中，我们将确定poly（A）尾长本身是否是调节这些mRNA翻译的决定因素，并将研究生物钟如何控制节奏翻译。这些都是重要的研究，因为调节poly（A）尾长的转录后机制对于产生适当的节律性蛋白质谱以及因此肝脏的适当节律性功能是至关重要的。

 DESCRIPTION (provided by applicant): Circadian clocks throughout the body drive rhythmic expression of thousands of genes, resulting in rhythms in biochemistry, physiology and behavior. Disruption of these rhythms in mammals has been shown to result in significant health problems. In addition to causing major deleterious effects on metabolism (including obesity and diabetes), increased risk of some types of cancer and cardiovascular problems, recent evidence has also shown a close tie between circadian clocks and affective disorders, sleep abnormalities and major depression. Although circadian control of transcription has been widely studied, recent data have demonstrated that post- transcriptional control, although much less well understood, is also critical for normal rhythmic protein expression profiles. One type of post transcriptional control is regulation of mRNA poly (A) tail length, which impacts the stability and translational regulation of mRNA. We have identified hundreds of mouse liver mRNAs that exhibit robust circadian rhythms in the length of their poly (A) tails. In many of these cases, the rhythmic tail lengths are the result of rhythmic cytoplasmic polyadenylation and deadenylation rhythms and many components of the cytoplasmic polyadenylation and deadenylation machinery are themselves under circadian control. Furthermore, the rhythmic poly (A) tails is closely correlated with the rhythmic protein expression. Therefore, the circadian clock regulates dynamic polyadenylation status of many mRNAs that can drive rhythmic protein expression independent of the steady-state levels of the message. In this proposal, we will explore the mechanisms that cause poly (A) tail rhythms and how these regulate the resulting protein production. In the first specific aim, we will test the hypothesis that the RNA-binding protein CPEB2 binds to specific mRNA targets and controls their polyadenylation state by coordinating the relative activities of deadenylases and poly (A) polymerases in a time of day-dependent manner. In the second specific aim, will test the hypothesis that the deadenylase Nocturnin is responsible for deadenylation and will determine whether deadenylation by Nocturnin leads to decay of those mRNAs that have tails that are modulated during the night phase. And in the third aim we will determine whether the poly (A) tail lengths are themselves the determining factor in regulating the translation of these mRNAs and will examine how the circadian clock controls rhythmic translation. These are important studies because the post-transcriptional mechanisms that regulate poly (A) tail lengths are critical for the generation of the appropriate rhythmic protein profiles and thus the appropriate rhythmic function of the liver.