CRYSTALLOGRAPHIC STUDIES OF VIRAL CYCLINS AND CDK6

近年来，调节细胞周期进程的关键酶已经 得到了广泛的鉴定和表征。的重大转变 真核细胞周期受细胞周期蛋白调控 通过磷酸化发挥调节功能的激酶(CDK) 参与细胞周期转变的关键蛋白质。为了确保适当的 细胞周期事件的计时和协调，CDK激酶的活性是 受到各种机制的严格控制，例如激活 脱辅酶与细胞周期蛋白形成复合体，激活和抑制 磷酸化，以及与抑制蛋白形成复合体。不 令人惊讶的是，它们在细胞周期控制中的关键作用，突变和 据报道，细胞周期蛋白和CDKs的过度表达是致癌的 事件。最近在致癌疱疹中发现的两种蛋白质 与人类D型细胞周期蛋白载体有密切同源性的病毒 这些观察结果。来自疱疹病毒Simiri的V-Cyclin和K- 卡波西肉瘤相关疱疹病毒(KSHV)的细胞周期蛋白显示24 分别有31%和31%的人与人类细胞周期蛋白D1和D3相一致， 分别进行了分析。它们与CDK4和CDK6结合，导致强烈的 视网膜母细胞瘤蛋白和组蛋白H1的激酶活性。这么高 未经许可的激酶活性水平最有可能导致对 HVS和KSHV疾病固有的细胞增殖。该序列 病毒细胞周期蛋白与D型细胞周期蛋白的同源性和相似性 在CDK激活中使病毒周期蛋白成为研究激活的好系统 CDK4和CDK6的作用机制，否则可能导致致癌事件 控制得当。此外，KSHV还参与了该病毒的发展。 卡波西肉瘤，尤其是艾滋病患者。因此，对这一现象的研究 两个同源的病毒细胞周期蛋白可能有助于理解 该病的发病机制和治疗。 短期目标是确定 V-Cyclin。长期目标是确定k-的结构。 Cyclin、CDK6的X射线结晶学研究及CDK6的络合物研究 与病毒周期蛋白结合，最终目的是确定结构 井。这些信息将有助于理解激活机制 引起各种疾病的病毒蛋白对宿主细胞CDK的影响 包括癌症。

In recent years, key enzymes that regulate cell cycle progression have been identified and characterized extensively. The major transition of the eucaryotic cell cycle are controlled by cyclin-dependent protein kinases (CDKs) that exert their regulatory function by phosphorylation of key proteins involved in cell cycle transitions. To ensure proper timing and coordination of cell cycle events, CDK kinase activity is tightly controlled by various mechanisms, such as activation of the apoenzyme by complex formation with cyclins, activating and inhibiting phosphorylations, and complex formation with inhibitory proteins. Not surprisingly from their key role in cell cycle control, mutations and overexpression of cyclins and CDKs have been reported to be oncogenic events. The recent discovery of two proteins from oncogenic herpes viruses that show close homology with human D-type cyclins supports these observations. V-cyclin from herpesvirus saimiri (HVS) and k- cyclin from Kaposi's sarcoma associated herpesvirus (KSHV) show 24 percent and 31 percent identity with human cyclin D1 and D3, respectively. They associate with CDK4 and CDK6, resulting in strong kinase activity toward retinoblastoma protein and histone H1. This high level of unlicensed kinase activity most likely induces deregulation of cell proliferation inherent to HVS and KSHV diseases. The sequence homologies between viral cyclins and D-type cyclins and the similarities in CDK activation make viral cyclins a good system to study activation mechanisms of CDK4 and CDK6, that might lead to oncogenic events if not properly controlled. Futhermore, KSHV is implicated in the development of Kaposi's sarcoma, especially in AIDS patients. Hence, studies of the two homologous viral cylclins may contribute to understanding the pathogenesis and treatment of this disease. The short term goal is to determine the three-dimensional structure of v-cyclin. The long-term goal is to determine the structures of k- cyclin, and CDK6 by x-ray crystallography and to study complexes of CDK6 with viral cyclins with the final aim of structure determination as well. This information will help to understand the activation mechanism of host cell CDKs by proteins from viruses that cause various diseases including cancer.