Circadian regulation of mitochondrial RNA polyadenylation

描述（由申请人提供）：生物钟是一种内部计时机制，它在时间上协调行为和生理的许多方面与昼夜周期。这些时钟控制着数千个基因，这些基因驱动细胞内的许多关键过程，包括许多代谢过程。此外，营养摄入和许多代谢过程也反馈调节中央时钟机制，时钟的破坏导致广泛的代谢功能障碍。生物钟的一个重要作用可能是在整个昼夜周期中暂时协调代谢程序，以提高效率并避免无效反应。在这个提议中，我们提供了证据，将时钟的影响扩展到细胞的另一个关键代谢成分-线粒体的氧化磷酸化系统。我们提出新的证据表明，昼夜节律蛋白夜曲素调节电子传递链的细胞色素c氧化酶（复合体IV）的活性。夜曲蛋白编码一种deadenylase，一种负责从mrna中去除聚a尾的酶，在本提案中，我们提供的数据表明，夜曲蛋白在线粒体中起作用（除了其在细胞质中的已知作用外）以转录后控制线粒体

DESCRIPTION (provided by applicant): Circadian clocks are internal timekeeping mechanisms that temporally coordinate many aspects of behavior and physiology with the diurnal cycle. These clocks control thousands of genes that drive many critical processes within the cell, including many metabolic processes. Furthermore, nutrient intake and many metabolic processes also feedback to regulate the central clock mechanism and disruption of the clock results in broad metabolic dysfunction. An important role of the clock may be to temporally coordinate metabolic programs throughout the circadian cycle to increase efficiency and avoid futile reactions. In this proposal, we provide evidence that expands the influence of the clock to yet another critical metabolic component of the cell - the oxidative phosphorylation system of the mitochondrion. We present new evidence demonstrating that the circadian protein Nocturnin is regulating the activity of cytochrome c oxidase (Complex IV) of the electron transport chain. Nocturnin encodes a deadenylase, an enzyme responsible for removing poly A tails from mRNAs, and in this proposal we present data that shows that Nocturnin works in the mitochondria (in addition to its known role in the cytoplasm) to post-transcriptionally control one of the mRNAs that is critical for Complex IV assembly and function. Based on these data, we propose three specific aims designed to test the general hypothesis that the circadian clock regulates oxidative phosphorylation through rhythmic Nocturnin deadenylation of mitochondria-encoded mRNAs. In the first specific aim, we will examine how Nocturnin intracellular localization is regulated and test whether alternative translation initiation regulates whether or not a mitochondrial targeting signal is added to the Nocturnin protein. In the second aim, we will examine the mechanism by which Nocturnin regulates Complex IV activity and mitochondrial oxidative phosphorylation. We will test whether Nocturnin is part of a "machine" that dynamically regulates mitochondrial mRNA poly A tail length and test whether this results in altered translation of the target mRNA. Finally, in the third aim, we will test whether these processes are directly regulated by the circadian clock and will determine the kinetics of Complex IV assembly at different times of day. Furthermore, we will test whether Nocturnin' s rhythmicity is important for proper functioning of the oxidative phosphorylation system using an inducible mouse model that expresses Nocturnin in a non-rhythmic manner. These proposed studies will uncover the mechanism behind this new and exciting role, for the circadian system control of the ATP generating system of the cell. One in 5000 humans have mutations that affect Complex IV assembly and activity resulting in severe disease, including encephalomyopathies, neurodegenerative Leigh syndrome, hypertrophic cardiomyopathies, and fatal lactic acidosis. Therefore, understanding how this system is modulated is of critical importance.