INTEGRATION OF ONCOGENIC SIGNALS BY THE NUCLEOLAR ARF-NPM NETWORK

摘要 核仁最初被描述为包含在特定染色体区域内的细胞器， 在过去的世纪里，沿着着细胞和癌症生物学知识的传授。一旦 作为核糖体生物合成的静态中心， 可见的细胞器是近年来建立的。哺乳动物中最活跃的居住者之一 核仁是ARF肿瘤抑制蛋白。自发现以来，ARF肿瘤背后的机制 抑制功能一直在深入研究中。最初被吹捧为真正的p53抑制剂， 负调节因子Mdm 2，最近的研究已经确定了ARF在抑制ARF中的p53独立作用。 在小鼠和人类中的肿瘤形成。最近的大部分工作都集中在小说的本地化， 核仁中的ARF，就转化性质而言，它是一种看似良性的细胞器。一个最小的身上 我们对ARF生物学的理解是ARF在核仁中的作用。很多实验室，包括我们的， 已经鉴定出核磷蛋白（NPM）原癌基因作为ARF的核仁结合伴侣。我们 初步数据表明，Tsc 1肿瘤抑制因子缺失所产生的过度生长信号， 刺激NPM和ARF两者的蛋白质表达以影响核糖体合成速率。 此外，基础核仁ARF蛋白与核仁中的NPM池相互作用， 基础ARF分子导致NPM功能失调和核糖体生物合成增加。损失 核仁ARF改变了核仁的景观，允许蛋白质，如p68 RNA解旋酶， 更容易与NPM相互作用，从而潜在地促进核糖体生物发生和细胞转化。我们 假设ARF存在于核仁中，通过感知 过度生长信号和停止不必要的NPM-p68活动。根据我们的初步数据和我们的声明， 假设，提出了三个具体的目标：1）确定致癌生长信号是如何解释的， 核仁ARF-NPM复合物，2）建立p68 RNA解旋酶的物理和功能相互作用 3）测定ARF在体外和体内充当核仁检查点蛋白的能力。项目叙述 ARF肿瘤抑制基因是人类癌症中第二常见的突变基因， 只到p53。我们刚刚开始了解这种关键的肿瘤抑制因子是如何发挥作用的， 防止不必要的细胞生长和增殖。我们试图了解背后的机制 ARF在体内调节p53非依赖性生长停滞的能力，并将这些发现转化为一种新的研究方法。 新的ARF靶向治疗可能会影响广泛的临床环境， 癌症患者。因此，鉴于ARF生物学的突变性，对其进行基础研究是适当的 人类癌症的发病率。

ABSTRACT Initially described as an organelle contained within specific chromosomal regions, the nucleolus has advanced through the past century imparting much knowledge about cell and cancer biology along the way. Once hindered with the label as being the static center of ribosome biogenesis, a newfound appreciation for this visible organelle has been established in recent years. One of the most dynamic occupants of the mammalian nucleolus is the ARF tumor suppressor protein. Since its discovery, the mechanism behind ARF's tumor suppressive function has been under intense investigation. Initially touted as a bona fide inhibitor of the p53 negative regulator, Mdm2, more recent studies have identified a p53-independent role for ARF in suppressing tumor formation in mice and humans. Much of the more recent work has focused on the novel localization of ARF in the nucleolus, a seemingly benign organelle in terms of transformation properties. One of the least understood aspects of ARF biology is what is ARF doing in the nucleolus. Numerous labs, including ours, have identified the nucleophosmin (NPM) proto-oncogene as a nucleolar binding partner of ARF. Our preliminary data demonstrates that hypergrowth signals emanating from the loss of the Tsc1 tumor suppressor stimulate the protein expression of both NPM and ARF in an effort to influence ribosome synthesis rates. Additionally, basal nucleolar ARF proteins interact with a pool of NPM in the nucleolus and acute loss of these basal ARF molecules results in dysregulated NPM function and increased ribosome biogenesis. Loss of nucleolar ARF alters the landscape of the nucleolus, allowing for proteins, such as the p68 RNA helicase, to interact more readily with NPM to potentially promote ribosome biogenesis and cell transformation. We hypothesize that ARF resides in the nucleolus to tightly regulate ribosome biogenesis through the sensing of hypergrowth signals and to halt unwarranted NPM-p68 activities. Based on our preliminary data and our stated hypothesis, three specific aims are proposed: 1) Determine how oncogenic growth signals are interpreted by the nucleolar ARF-NPM complex, 2) Establish the physical and functional interaction of the p68 RNA helicase with NPM, and 3) Determine the in vitro and in vivo ability of ARF to act as a nucleolar checkpoint protein. PROJECT NARRATIVE The ARF tumor suppressor is the second most commonly mutated gene in human cancers, second only to p53. We are just beginning to appreciate how this critical tumor suppressor functions to prevent unwarranted cell growth and proliferation. We seek to understand the mechanism behind ARF's ability to regulate p53-independent growth arrest in vivo and to move these findings into a more clinical setting where novel ARF-targeted therapeutics might affect a broad spectrum of cancer patients. Thus, basic research into ARF biology is appropriate given its mutational prevalence in human cancers.