Regulatory Enzymes and Systems in Cell Cycle Control

项目总结/摘要 这项拟议中的研究探索了支配真核细胞分裂的迷人的调控系统 周期细胞周期控制系统是基于主要的调节酶，包括细胞周期蛋白依赖的 蛋白激酶（Cdks）和称为后期促进复合物或环体（APC/C）的泛素连接酶。 随着细胞通过细胞分裂步骤的进展，连续的Cdk-细胞周期蛋白复合物修饰了数百个 蛋白质，导致染色体在S期复制和重复染色体上的对齐， M期纺锤体。APC/C然后触发几个关键监管机构的破坏，释放 染色体分离和胞质分裂的戏剧性事件。一种关键的APC/C基质是securin， 蛋白酶的抑制剂，分离酶; APC/C介导的securin破坏释放分离酶， 将复制的染色体结合在一起的粘着蛋白复合体。细胞周期事件的精确定时需要 Cdks和APC/C被激活并以特定的顺序修饰它们的靶标。生化 该顺序下的机制是本申请中描述的研究的中心焦点。工作 将探讨各种各样的有趣的机制问题Cdk和APC/C功能。萌芽研究 酵母将解决复杂的信息处理，可以通过多位点磷酸化来实现 的Cdk底物，专注于控制细胞周期蛋白基因表达的转录调节因子。多行 研究将解决APC/C与其底物结合激活剂一起 亚单位，控制特定目标的破坏。一种新开发的单分子方法将提供 APC/C-底物相互作用的严格定量测量，提供了对 底物亲和力，是细胞周期事件有序化的基础。生物化学和结构方法， 人类蛋白质将被用来阐明APC/C激活子亚单位被加载到 APC/C通过伴侣蛋白TRiC/CCT。类似的方法将用于确定机制， 人类分离酶识别其底物的机制，以及securin和其他调节蛋白的机制。 蛋白质抑制分离酶催化功能。从这些研究中获得的信息将提供重要的 对细胞周期进程控制的新见解，从而将增强我们对疾病的理解， 如细胞周期控制或染色体分离缺陷癌症。这些研究还将 阐明在整个细胞生物学和人类疾病中具有重要意义的一般调节机制。

PROJECT SUMMARY/ABSTRACT The proposed research explores the fascinating regulatory system that governs the eukaryotic cell division cycle. The cell-cycle control system is based on master regulatory enzymes that include the cyclin-dependent protein kinases (Cdks) and a ubiquitin ligase called the anaphase-promoting complex or cyclosome (APC/C). As the cell progresses through the steps of cell division, sequential Cdk-cyclin complexes modify hundreds of proteins, leading to chromosome duplication in S phase and alignment of duplicated chromosome on the mitotic spindle in M phase. The APC/C then triggers destruction of several key regulators, unleashing the dramatic events of chromosome segregation and cytokinesis. One critical APC/C substrate is securin, an inhibitor of the protease, separase; APC/C-mediated securin destruction releases separase to cleave the cohesin complex holding duplicated chromosomes together. The precise timing of cell cycle events requires that Cdks and the APC/C are activated and modify their targets in a specific order. The biochemical mechanisms underlying this order are the central focus of the research described in this application. The work will explore a diverse array of interesting mechanistic problems in Cdk and APC/C function. Studies in budding yeast will address the complex information processing that can be achieved through multi-site phosphorylation of Cdk substrates, focusing on transcriptional regulators that govern cyclin gene expression. Multiple lines of investigation will address the mechanisms by which the APC/C, together with its substrate-binding activator subunit, controls the destruction of specific targets. A newly developed single-molecule approach will provide rigorous quantitative measurements of APC/C-substrate interactions, providing insight into the variations in substrate affinity that underlie the ordering of cell cycle events. Biochemical and structural approaches with human proteins will be used to unravel the mechanisms by which the APC/C activator subunit is loaded onto the APC/C by the chaperonin TRiC/CCT. Similar approaches will be used to determine the mechanisms by which human separase recognizes its substrates, and the mechanisms by which securin and other regulatory proteins inhibit separase catalytic function. The information gained from these studies will provide important new insights into the control of cell-cycle progression, and will thereby enhance our understanding of diseases, such as cancer, in which cell-cycle control or chromosome segregation is defective. These studies will also illuminate general regulatory mechanisms of major importance throughout cell biology and human disease.