Regulation Of A Novel Xenopus Polo-Like Kinase 1 Substrate

描述（由申请人提供）：polo样激酶1 （PLK1）在有丝分裂的多个步骤中起关键作用。最近，PLK1被认为是一种致癌基因，并已成为抗癌药物的潜在靶点。尽管在了解PLK1在细胞周期控制中的作用方面已经取得了重大进展，但在一些重要的有丝分裂事件中，PLK1执行其功能的分子机制仍然难以捉摸，这主要是由于缺乏确定的PLK1生理底物。该申请人提出了一种新的非洲爪蟾样马球激酶1 （PLX1）底物的初步数据。该底物已被鉴定为去泛素酶，其哺乳动物同源物特异性修饰组蛋白并影响细胞分裂。本研究的长期目标是确定PLX1通过磷酸化去泛素酶来调节细胞周期进程的新机制。为了本应用的目的，近期或短期目标是阐明PLX1对新型底物的调控，并确定这种磷酸化对去泛素酶的影响。由于cyclin B/Cdk1 （MPF）也被认为是去泛素酶的磷酸化激酶，我们的假设是PLX1在体内与MPF协同调节去泛素酶的活性和可能的定位，从而影响细胞周期的进展。该假设将通过与以下目标相关的活动进行检验：(1)确定PLX1和MPF磷酸化的去泛素酶的主要位点；(2)确定PLX1磷酸化对该底物活性和定位的影响。PLX1磷酸化激活去泛素酶并改变其定位的可能性将被研究；(3)确定PLX1磷酸化底物是否需要MPF启动。在许多情况下，PLX1磷酸化需要由一个不同的激酶启动PLX1底物，以产生polo box结构域的结合位点，polo box结构域是polo样激酶家族中的一种独特结构。拟议的研究预计将进一步积累初步数据，并在项目结束时提交一份完整的研究建议。

DESCRIPTION (provided by applicant): Polo-like kinase 1 (PLK1) plays a pivotal role at multiple steps of mitosis. Recently, PLK1 was implicated as an oncogene and has emerged as a potential target for anti-cancer drugs. Although significant progress has been made towards the understanding of the roles of PLK1 in cell cycle control, the molecular mechanisms by which it executes its functions during some important mitotic events remains elusive, largely due to the lack of identified physiological substrates for PLK1. This applicant presents preliminary data that focuses on a novel substrate for Xenopus polo- like kinase 1 (PLX1). The substrate has been identified and characterized as a deubiquitinase, whose mammalian homologue specifically modifies histone and affects cell division. The long- term goal of this proposed research is to define a novel mechanism by which PLX1 regulates the progression of cell cycle through the phosphorylation of this deubiquitinase. For the purposes of this application, the immediate or short-term goal is to clarify PLX1 regulation of the novel substrate and to determine the impact of such phosphorylation on the deubiquitinase. Since cyclin B/Cdk1 (MPF) is also suggested as a phosphorylating kinase for the deubiquitinase, our hypothesis is that PLX1 regulates the activity and possibly the localization of this deubiquitinase in vivo in coordination with MPF, which in turn, affects the progression of cell cycle. The hypothesis will be tested through the activities associated with following objectives: (1) Identify the main sites in the deubiquitinase phosphorylated by PLX1 and MPF; (2) Determine the impact of PLX1 phosphorylation on activity and localization of this substrate. The possibility that PLX1 phosphorylation activates the deubiquitinase and changes its localization will be examined; and (3) Determine whether phosphorylation of the substrate by PLX1 requires MPF priming. In many cases, PLX1 phosphorylation requires the priming of a PLX1 substrate by a distinct kinase in order to generate a binding site for polo box domain, a unique structure in the polo-like kinase family. The proposed studies are expected to result in accumulation of further preliminary data and lead to the submission of a full research proposal by the end of the project. PUBLIC HEALTH RELEVANCE: Polo-like kinase 1 is a key cell cycle regulator and has recently emerged as a promising target for anti-cancer drugs. This application proposes to study the regulation of a novel substrate for polo-like kinase 1. The study is expected to reveal a new mechanism of cell cycle control and may also provide a foundation for developing innovative strategies for treating human diseases such as cancer.