Monitoring mechanisms in mammalian ribosome biogenesis

描述(由申请人提供)： 合成新的核糖体是一种基本的细胞活动，越来越清楚的是，核糖体的生物发生在癌症和人类疾病中扮演着重要的角色。然而，这一高度复杂的过程及其与其他细胞通路的联系的分子机制仍未被充分了解，特别是在哺乳动物系统中。最近的证据表明，哺乳动物细胞拥有一种监视系统，该系统将核糖体合成的扰动传递给肿瘤抑制因子p53。目前尚不清楚核糖体组装中的错误是如何被识别的，以及核糖体生物发生机制中的哪些成分介导了对p53途径的信号传递。我们试图通过分析新发现的核仁GTP结合蛋白(GTP结合蛋白)Nog1和Nug1A/B来了解监控哺乳动物细胞核糖体生物发生的机制。最近的实验证据表明，这些GTP酶的功能对于60S核糖体亚基的合成是必不可少的，也暗示它们是核糖体合成和增殖控制通路之间的潜在信号链接。这些研究旨在阐明哺乳动物核仁GTP酶在核糖体生物发生监测中的作用，并深入了解其作用的分子机制。我们将首先回答两个问题，以评估核仁GTP酶的监测功能。小鼠Nog1和Nug1A/B在rRNA成熟中起什么作用？它们的功能如何有助于核糖体生物发生的准确性和对P53网络的信号传递？通过结合生物化学和遗传学方法，我们将进一步研究代表该群体的模型NOG1的分子机制。鸟嘌呤核苷酸结合和水解在该GTP酶的活性中起什么作用？哪些蛋白质是Nog1功能的效应者和调节者，它们如何影响其GTPase循环？总之，这些研究将为一组新的GTP结合蛋白提供重要的新信息，产生对核糖体组装的机械性见解，并有助于我们理解核糖体生物发生与哺乳动物细胞增殖控制之间的联系。

DESCRIPTION (provided by applicant): Synthesis of new ribosomes is an essential cellular activity and it is becoming increasingly clear that ribosome biogenesis plays an important role in cancer and human disease. However, molecular mechanisms of this highly complex process and its links to other cellular pathways remain inadequately understood, especially in a mammalian system. Recent evidence indicates that mammalian cells possess a surveillance system that communicates perturbations in ribosome synthesis to the tumor suppressor p53. It is currently unknown how errors in ribosome assembly are recognized and which components in the ribosome biogenesis machinery mediate signaling to the p53 pathway. We seek to understand the mechanisms that provide monitoring of ribosome biogenesis in mammalian cells through analysis of the newly discovered nucleolar GTP-binding proteins (GTPases) Nog1 and Nug1A/B. Recent experimental evidence shows that the function of these GTPases is essential for synthesis of 60S ribosomal subunits and also implicates them as potential signaling links between ribosome synthesis and proliferation control pathways. The studies proposed here are designed to elucidate the role of the mammalian nucleolar GTPases in surveillance of ribosome biogenesis and to gain insight into the molecular mechanisms of their action. We will begin by addressing two questions to assess the monitoring function of the nucleolar GTPases. What is the role of mouse Nog1 and Nug1A/B in rRNA maturation? How does their function contribute to the accuracy of ribosome biogenesis and signaling to the p53 network? By using a combination of biochemical and genetic approaches, we will further investigate the molecular mechanisms of a model representative of the group, Nog1. What role do guanine nucleotide binding and hydrolysis play in the activities of this GTPase? What proteins serve as effectors and regulators of Nog1 function and how do they influence its GTPase cycle? Collectively, these studies should provide significant new information on a novel group of GTP-binding proteins, yield mechanistic insights into ribosome assembly and contribute to our understanding of the link between ribosome biogenesis and proliferation control in mammalian cells.