Structural mechanisms of assembling, activating and inhibiting CDK4

细胞的生长和分裂在分子水平上受到一系列酶的严格控制，其中包括细胞周期蛋白依赖性蛋白激酶(CDKs)。这些酶按顺序开启和关闭，以确保细胞分裂在所需的时间开始和停止。虽然在序列上密切相关，但对CDK家族不同成员的生物学研究表明，每个成员都有独特的特性。特别是，它们的活性既可以通过与不同的调节蛋白家族结合来调节，也可以通过在特定的氨基酸侧链上添加磷酸基团来修改蛋白质序列来调节。我们的工作，使用X射线结晶学技术，使我们能够在原子分辨率下看到这些分子的结构，从而了解它们之间的区别。我们工作的第一个目的是了解细胞周期蛋白依赖性激酶抑制剂(CKI)家族的成员如何与CDK家族中的一个成员CDK4结合，并促进其与其调节因子Cyclin D的组装(导致活性酶复合体)或抑制其活性。CDK4与CDK家族其他成员的不同之处还在于它的底物数量非常有限。我们工作的第二个目标是理解为什么会这样。CDK活性异常与癌症、神经系统疾病和类风湿性关节炎有关。特别是，由于调节CDK4活性的蛋白质的基因突变而导致的CDK4活性水平升高，在许多癌症中普遍存在，并与不良预后有关。近年来，对导致疾病的特定缺陷的了解导致了针对特定目标的令人兴奋的新药(例如，治疗癌症的药物格列卫、易瑞沙和赫赛汀)。一些CDK选择性抑制剂正在进行癌症治疗的临床试验。这些试剂都通过与CDK活性部位结合来阻断CDK活性。阻断CDK/细胞周期蛋白复合体的其他相互作用的化合物是CDK导向治疗的替代靶点。本项目中描述的工作，阐述了介导底物与CDK和CDK调节蛋白结合的相互作用，将有助于此类化合物的进一步开发，并可能揭示抑制剂开发的更多靶点。

The growth and division of cells is strictly controlled at the molecular level by a series of enzymes that include the cyclin dependent protein kinases (CDKs). These enzymes are switched on and off in an orderly sequence, to ensure that cell division starts and stops at the required time. Though closely related in sequence, biological studies of the different members of the CDK family have revealed that each has unique properties. In particular, their activities can be regulated both by association with different families of regulatory proteins and by modification of the protein sequence by addition of a phosphate group to specific amino acid side chains. Our work, using the technique of X-ray crystallography, allows us to see the structures of these molecules at atomic resolution and so to learn how they differ from each other. The first aim of our work is to understand how members of the family of cyclin-dependent kinase inhibitors (CKIs) can bind to one member of the CDK family called CDK4 and either promote its assembly with its regulator cyclin D (resulting in an active enzyme complex) or inhibit its activity. CDK4 is also distinguished from other members of the CDK family in that it has a very limited number of substrates. The second aim of our work is to understand why this is the case. Aberrant CDK activity has been linked to cancer, neurological diseases, and rheumatoid arthritis. In particular, elevated levels of CDK4 activity, resulting from mutations in the genes for the proteins that regulate its activity, is commonly found in a number of cancers and is associated with a poor prognosis. In recent years, understanding a particular defect that leads to disease has led to exciting new medicines directed towards a particular target (e.g. the drugs Gleevec, Iressa and Herceptin for cancer treatment). A number of CDK-selective inhibitors are in clinical trials for the treatment of cancer. These agents all act by binding to the CDK active site to block CDK activity. Compounds that block other interactions made by CDK/cyclin complexes represent an alternative target for CDK-directed therapies. The work described in this project, to elaborate the interactions that mediate the binding of substrates to CDKs and CDK-regulatory proteins, will aid the further development of such compounds and may also reveal additional targets for inhibitor development.