Role of the SCF/FBX011 ubiquitin ligase in the control of cell proliferation

描述(由申请人提供)：细胞周期中的单向进展依赖于泛素-蛋白酶体系统(UPS)对关键调节因子的特定、快速和时间控制的蛋白分解。E3泛素连接酶赋予UPS底物特异性。因此，这些酶功能的改变导致包括癌症在内的多种疾病的发展也就不足为奇了。SCF(Skp1，Cul1，F-box Protein)复合体(又称Cul1环连接酶或CRL1)是一类E3泛素连接酶家族，参与基因转录、蛋白质合成、细胞分裂、DNA损伤检查点、生物钟和细胞凋亡等重要细胞通路。F-box蛋白通过作为受体直接与底物结合和募集，在SCF复合体中发挥着关键作用。虽然已经确定了某些F-box蛋白的特征，但它们中的大多数还没有与它们的同源底物匹配，因此被定义为“孤儿”。FBXO11是一种参与调节细胞命运决定的孤儿F-box蛋白，编码该蛋白的基因突变与人类和动物模型的病理条件的发生和发展有关。利用无偏倚的蛋白质组筛选，我们已经确定CDT2是SCFFBXO11的一种新的、可能的底物。CDT2属于DCAF蛋白家族，是被称为CRL4(CUL4环连接酶)的多亚单位E3复合体的底物受体。CRL4CDt2控制细胞增殖的关键调控因子(CDt1、p21、Set8等)的降解。无论是在正常细胞还是癌细胞中；然而，控制CDT2本身降解的机制仍然不清楚。在目前的应用中，我们将研究FBXO11和Cdt2共同调控的分子机制和途径。为此，我们将解决SCFFBXO11如何、何时(AIM1)以及为什么(AIM2)控制CdT2的降解。综上所述，我们的研究将为控制细胞增殖和分化的调控电路提供新的见解。此外，它们可能为未来的研究提供一个平台，以探索FBXO11和CDT2在各种细胞增生性疾病中的作用。这项拟议的研究是美国国立卫生研究院R37-CA076584(07/01/1-06/30/2016)拨款的延伸，并代表了与Mario Rossi博士的合作努力，Mario Rossi博士是布宜诺斯艾利斯-CONICET生物医学研究所的小组负责人，阿根廷Max Planck协会的合作伙伴研究所与这项申请相关的低收入到中等收入国家(LMIC)网站，项目的最大部分将在Rossi博士的监督下进行。

DESCRIPTION (provided by applicant): Unidirectional progression through the cell cycle depends on the specific, rapid, and temporally controlled proteolysis of key regulators by the ubiquitin-proteasome system (UPS). E3 ubiquitin ligases confer substrate specificity to the UPS. Therefore, it is not surprising that alteration of the functions of these enzymes contribute to the development of a wide variety of diseases, including cancer. SCF (Skp1, Cul1, F-box protein) complexes (also known as Cul1-Ring-ligases or CRL1) represent a family of E3 ubiquitin ligases involved in crucial cellular pathways as gene transcription, protein synthesis, cell division, DNA-damage checkpoints, the circadian clock, and apoptosis. F-box proteins play a pivotal role in the SCF complex by functioning as receptors that directly bind to and recruit substrates. Although certain F-box proteins have been characterized, most of them have not yet been matched to their cognate substrates and, therefore, are defined "orphan." FBXO11 is an orphan F-box protein involved in regulating cell fate determination, and mutations of the gene encoding this protein have been associated with the onset and progression of pathological conditions both in humans and in animal models. Using unbiased proteomic screens, we have identified Cdt2 as a novel, putative substrate of SCFFBXO11. Cdt2 belongs to the family of DCAF proteins that are the substrate receptors of multi-subunit E3 complexes known as CRL4 (Cul4-Ring- ligase). CRL4Cdt2 controls the degradation of key regulators of proliferation (Cdt1, p21, Set8, etc.) in both normal and cancer cells; however, the mechanisms controlling the degradation of Cdt2 itself have remained unknown. Under the present application, we will study the molecular mechanisms and pathways regulated by both FBXO11 and Cdt2. To this end we will address how, when (Aim1), and why (Aim2) the SCFFBXO11 control the degradation of Cdt2. Taking together, our studies will provide novel insights into the regulatory circuits that control cell proliferation and differentiation. Moreover, they may offer a platform for future studies to explore the role of FBXO11 and Cdt2 in various cellular proliferative disorders. The proposed research is an extension of the NIH grant R37-CA076584 (07/01/1-06/30/2016) and represents a collaborative effort with Dr. Mario Rossi, a Group Leader at the BioMedicine Institute of Buenos Aires-CONICET-Partner Institute of the Max Planck Society in Argentina, the low- to middle-income countries (LMIC) site associated with this application, where the largest part of the project will be carried out under the supervision of Dr. Rossi.