Novel Substrates of SCF Ubiquitin Ligases in Cell Cycle Control and Cancer

泛素系统是细胞过程的主要调节机制，其中速度， 特殊性和时机是至关重要的。泛素介导的关键底物蛋白降解控制细胞 周期进程，信号转导通路，分化，细胞凋亡，DNA修复和 免疫反应。这一过程是由一台多功能机器介导的，该机器由一个监管机构 泛素靶向组件和效应器蛋白质降解引擎。监管 以泛素为靶标的成分本身由以下组成 一些多聚体元素(例如，SCFubiquitin连接酶复合体)贡献了很大一部分 这一过程所固有的特殊性。在人类中，有68个SCFligase，每个都具有 通过不同的F-盒蛋白亚基，通过直接招募底物来提供特异性 连接酶的其余部分，最终进入泛素结合酶。值得注意的是，只有三个 在68个人SCFubiquitin连接酶中(包含F-box蛋白UTrcp、Fbw7和Skp2， 分别)具有成熟的底物，其中许多参与细胞周期控制。 剩余的65F-box蛋白被认为是“孤儿”，因为它们的底物仍在等待 发现号。 我们最近开发了一种新的免疫纯化策略，可以丰富底物 对F-box蛋白进行质谱分析。我们将系统地识别 具有生物学意义的人孤儿F-盒蛋白底物(特定目标1)。因为我们的 研究兴趣，我们将特别关注那些孤儿F-盒蛋白，我们的初步 结果表明，它参与了细胞周期控制和癌症的发生。在目标2下，我们将验证 目标1中确定的生物学意义最大的底物。 鉴于它们在调节细胞增殖方面的关键作用，SCFligase通常是癌症的靶点- 相关的放松管制和参与致癌转化。因此，所获得的信息 来自拟议的研究将与癌症生物学和其他增殖性疾病直接相关 疾病。

The ubiquitin system is a major regulatory mechanism of cellular processes in which speed, specificity, and timing are critical. Ubiquitin-mediated proteolysis of key substrates controls cell cycle progression, signal transduction pathways, differentiation,apoptosis, DNA repair and the immune response. This process is mediated by a multimericmachine, composed of a regulatory ubiquitin-targeting component and an effector protein degradation engine. Theregulatory component, which targets ubiquitin to proteins destined for degradation, is itself composed of several multimeric elements (e.g., the SCFubiquitin ligase complexes) that contribute much of the specificity inherent in the process. In humans, there are sixty-eight SCFligases, each characterized by a different F-boxprotein subunit that provides specificity by directly recruiting the substrate to the rest of the ligase and,ultimately, to the ubiquitin-conjugating enzyme. Notably, only three out of 68 human SCFubiquitin ligases (containing the F-box proteins UTrcp, Fbw7 and Skp2, respectively) have well-established substrates, many of which are involved in cell cycle control. The remaining 65F-box proteins are considered as "orphan" since their substrates still await discovery. We have recently developed a novel immunopurification strategy that enriches for substrates of F-box proteins followed by mass spectrometry analysis. We will systematicallyidentify biologically significantsubstrates of human orphan F-boxproteins (Specific Aim 1). Because of our research interest, we will focus particularly on those orphan F-boxproteins that our preliminary results suggest to be involved in cell cycle control and cancer. Under Aim 2,we will validate the biologically most significantsubstrates identifiedunder Aim 1. Given their critical role in regulating cell proliferation, SCFligases are often the target of cancer- related deregulation and involved in oncogenic transformation. Therefore,the information gained from the proposed studies will be of direct relevance to cancer biology and other proliferative diseases.