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

描述（由申请人提供）：细胞周期的单向进展取决于泛素-蛋白酶体系统（UPS）对关键调节因子的特异性、快速和暂时控制的蛋白质水解。E3泛素连接酶赋予UPS底物特异性。因此，这些酶功能的改变有助于包括癌症在内的各种疾病的发展，这并不奇怪。SCF （Skp1, Cul1， F-box蛋白）复合物（也称为Cul1-环连接酶或CRL1）代表E3泛素连接酶家族，参与关键的细胞途径，如基因转录，蛋白质合成，细胞分裂，dna损伤检查点，生物钟和凋亡。F-box蛋白作为直接结合和招募底物的受体，在SCF复合体中起着关键作用。虽然某些F-box蛋白已经被表征，但它们中的大多数尚未与其同源底物匹配，因此被定义为“孤儿”。FBXO11是一种孤儿F-box蛋白，参与调节细胞命运的决定，编码该蛋白的基因突变与人类和动物模型中病理状况的发生和进展有关。使用无偏倚的蛋白质组学筛选，我们已经确定Cdt2是SCFFBXO11的一个新的假定底物。Cdt2属于DCAF蛋白家族，是被称为CRL4 （Cul4-Ring-连接酶）的多亚基E3复合物的底物受体。CRL4Cdt2在正常细胞和癌细胞中控制增殖关键调控因子（Cdt1、p21、Set8等）的降解；然而，控制Cdt2自身降解的机制仍然未知。在本项目下，我们将研究FBXO11和Cdt2共同调控的分子机制和途径。为此，我们将讨论SCFFBXO11如何，何时（Aim2）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回路提供新的见解。此外，它们可能为未来研究FBXO11和Cdt2在各种细胞增殖性疾病中的作用提供平台。拟议的研究是美国国立卫生研究院拨款R37-CA076584（07/01/1-06/30/2016）的延伸，代表了与阿根廷马克斯普朗克学会（低收入和中等收入国家（LMIC）站点）生物医学研究所的组长Mario Rossi博士的合作努力，其中项目的大部分将在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.