Circadian dynamics of cytoplasmic mRNA polyadenylation and deadenylation

 描述(申请人提供)：整个身体的生物钟驱动数以千计的基因有节奏地表达，导致生物化学、生理和行为的节奏。哺乳动物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、睡眠异常和严重抑郁症之间存在密切联系。虽然转录的昼夜节律控制已经被广泛研究，但最近的数据表明，转录后控制，尽管了解得很少，但对正常的有节奏的蛋白质表达谱也是至关重要的。一种类型的帖子 转录调控是对信使核糖核酸Poly(A)尾长的调节，影响核糖体的稳定性和稳定性。 信使核糖核酸的翻译调控我们已经确定了数百个小鼠肝脏的mRNAs，它们的Poly(A)尾巴的长度表现出强劲的昼夜节律。在许多这样的案例中， 有节律性的尾巴长度是细胞质多聚腺苷和死烯基化节律的结果，细胞质多腺苷和死烯基化机制的许多组成部分本身都受到昼夜节律的控制。此外，节律性Poly(A)尾巴与节律性蛋白的表达密切相关。因此，生物钟调节许多mRNAs的动态多聚腺苷基化状态，这些mRNAs可以驱动有节奏的蛋白质表达，而不依赖于信息的稳态水平。在这项提案中，我们将探索导致Poly(A)尾部节律的机制以及这些机制如何调节由此产生的蛋白质生产。在第一个特定的目标中，我们将检验这样的假设，即RNA结合蛋白CPEB2与特定的mRNA靶标结合，并通过以一种时间依赖的方式协调死烯基酶和聚(A)聚合酶的相对活性来控制其多腺化状态。在第二个特定目标中，将检验死烯基酶Nocturin负责死烯基化的假设，并将确定Nocturin的死烯基化是否导致那些在夜间阶段调制有尾巴的mRNAs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mRNAs翻译的决定因素，并将研究生物钟如何控制有节奏的翻译。这些都是重要的研究，因为调节Poly(A)尾巴长度的转录后机制对于产生适当的有节奏的蛋白质谱至关重要，从而对肝脏的适当有节奏的功能至关重要。

 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.