Regulation of Gene Expression by microRNAs in C. elegans

描述（由申请人提供）：通过一大类小（约 22nt）非编码 microRNA 对基因表达的控制已成为动物发育和疾病中转录后基因调控的新模式。 microRNA 诱导的沉默复合物 (miRISC) 通过部分碱基配对引导 microRNA 到达靶 mRNA 的 3<UTR，并导致翻译抑制和/或靶标降解。然而，目标识别和结合的步骤以及 miRISC 和其他 RNA 相关因子的作用仍然是活跃的研究领域。在本提案中，我们将确定在线虫秀丽隐杆线虫中结合 microRNA 及其靶标的新型蛋白质复合物的功能。该复合物包括 AIN-1（miRISC 的保守成员）以及三个具有冷休克结构域 (CSD) 的高度保守的 RNA 结合蛋白。我们假设 CSD 蛋白是抑制 microRNA 靶标表达的关键因素。为了阐明 CSD 蛋白的功能，我们将研究重点放在秀丽隐杆线虫身体肌肉中 miR-1 mRNA 靶标的调节上。我们之前关于 miR-1 及其对神经肌肉接头处突触信号传导的调节的工作为我们当前的提议建立了实验框架。我们将测试 miR-1 靶标表达、与 AIN-1 复合物结合以及招募到 P 体中对 CSD 蛋白的要求。我们将在以下两个目标中检验我们的假设： 在目标 1 中，我们将研究 CSD 蛋白在调节 miR-1 靶标表达和与 AIN-1 复合物结合中的功能。我们假设 CSD 蛋白直接或间接地将 miR-1 靶标 mRNA 募集至 AIN-1 复合物，以进行后续的靶标抑制。在目标 2 中，我们将测试 CSD 蛋白在 AIN-1 复合物形成和招募到 P 体（抑制 microRNA 靶 mRNA 的细胞质中心）中的作用。我们假设 CSD 蛋白与 mRNA 底物的结合是 AIN-1 复合物形成和靶向 P 体的必需步骤。最后，我们将测试单个 CSD 蛋白是否形成独特的模块化 AIN-1 复合物的假设，这或许是调节 microRNA 靶标子集的一种方法。我们期望这些研究能够深入了解 microRNA 靶标如何被识别并指定用于翻译抑制或降解的保守机制。

DESCRIPTION (provided by applicant): The control of gene expression by the large class of small (~22nt), noncoding microRNAs has emerged as a new mode of post-transcriptional gene regulation in animal development and disease. The microRNA-induced silencing complex (miRISC) guides microRNAs to the 3< UTR of target mRNAs through partial base pairing and leads to translational inhibition and/or target degradation. However, the steps of target recognition and binding, and the role of miRISC and other RNA-associated factors remain active areas of investigation. In this proposal we will determine the function of a novel protein complex that binds microRNAs and their targets in the nematode, C. elegans. This complex includes AIN-1, a conserved member of miRISC, as well as three highly conserved RNA binding proteins with Cold Shock Domains (CSD). We hypothesize that the CSD proteins function as key factors for repressing the expression of microRNA targets. To elucidate the function of the CSD proteins, we will focus our studies on the regulation of miR-1 mRNA targets in the body muscle of C. elegans. Our previous work on miR-1 and its regulation of synaptic signaling at the neuromuscular junction establishes the experiment framework for our current proposal. We will test the requirement for the CSD proteins in miR-1 target expression, binding to the AIN-1 complex, and recruitment to P bodies. We will test our hypothesis in the following two aims: In Aim 1, we will investigate the function of the CSD proteins in the regulation of miR- 1 target expression and binding to the AIN-1 complex. We hypothesize that the CSD proteins recruit the miR-1 target mRNAs, directly or indirectly, to the AIN-1 complex for subsequent target repression. In Aim 2, we will test the role of the CSD proteins in AIN-1 complex formation and recruitment to the P bodies, the cytoplasmic centers for repression of microRNA target mRNAs. We hypothesize that binding of mRNA substrates by the CSD proteins is a required step for AIN-1 complex formation and targeting to P bodies. Finally, we will test the hypothesis of whether individual CSD proteins form distinct, modular AIN-1 complexes, perhaps as a way to regulate subsets of microRNA targets. We expect that these studies will provide insights into the conserved mechanisms of how microRNA targets are recognized and designated for translational inhibition or degradation.