REGULATION OF MITOSIS BY PROTEOLYSIS IN YEAST

描述：在所有真核生物中，进入S期和有丝分裂都是被触发的 通过蛋白激酶，其活性取决于调控的细胞周期蛋白亚基 (细胞周期蛋白依赖性激酶；CDKs)。不同类型的CDK启动 细胞周期的不同事件。因此，这一点至关重要。 它们的活动被限制在适当的细胞周期阶段。 泛素依赖的有丝分裂周期蛋白分解在 限制有丝分裂CDK的活性。有丝分裂周期蛋白分解 在有丝分裂结束时使有丝分裂的CDK失活，并阻止其 在整个G1中积累。在S期和有丝分裂早期，有丝分裂 细胞周期蛋白分解被抑制，使有丝分裂的CDK积聚。 这项建议的目标是：(1)确定(S)的途径 激活有丝分裂周期蛋白分解；(2)确定CDKs的作用 抑制有丝分裂周期蛋白分解；以及(3)鉴定基因 S期抑制有丝分裂周期蛋白分解所需 早期有丝分裂。为了表征蛋白水解酶的激活途径(S)， 在这一过程中，基因将被识别出具体的缺陷。这些 分析将利用检测来激活蛋白分解和维持 阿蒙博士最近开发的蛋白质分解技术。使用这些化验方法， 推测的酪氨酸磷酸酶cdc14已经被鉴定为 特别需要激活，但对于维护来说却是必不可少的 有丝分裂周期蛋白分解。CDC14在有丝分裂激活中的作用 我们将详细描述细胞周期蛋白的降解作用。两种方法将是 研究CDKs在抑制有丝分裂周期中的作用 S期的蛋白分解和早期有丝分裂。(1)生化实验 我将讨论CDK的磷酸化是否直接抑制蛋白分解 进程。(2)基因方法将识别抑制所需的基因 有丝分裂周期蛋白在S期和有丝分裂早期的蛋白分解。 不受控制的细胞周期蛋白表达可能是致命的。它已链接到 癌变：细胞周期蛋白过度表达是卵巢癌的一个显著特征 某些肿瘤，包括乳腺癌。识别和表征 调控网络，如有丝分裂周期蛋白分解，限制 这些蛋白质的活性将为发展 癌症诊断和治疗学。

DESCRIPTION: In all eukaryotes, entry into S phase and mitosis is triggered by protein kinases, whose activity depends on regulatory cyclin subunits (cyclin-dependent kinases; Cdks). Different types of Cdks initiate different events of the cell cycle. It is therefore critically important that their activities are restricted to the appropriate cell cycle stages. Ubiquitin-dependent proteolysis of mitotic cyclins plays a key role in restricting the activity of the mitotic Cdks. Mitotic cyclin proteolysis inactivates mitotic Cdks at the end of mitosis and prevents their accumulation throughout G1. During S phase and early mitosis, mitotic cyclin proteolysis is inhibited, allowing mitotic Cdks to accumulate. The goals of this proposal are: (1) to identify the pathway(s) of activation of mitotic cyclin proteolysis; (2) to determine the role of Cdks in repression of mitotic cyclin proteolysis; and (3) to identify genes required for repression of mitotic cyclin proteolysis during S-phase and early mitosis. To characterize the pathway(s) of activation of proteolysis, genes will be identified specifically defective in this process. These analyses will utilize assays for activation of proteolysis and maintenance of proteolysis, recently developed by Dr. Amon. Using these assays, the putative tyrosine phosphatase Cdc14 has already been identified as being specifically required for activation but dispensable for maintenance of mitotic cyclin proteolysis. The role of CDC14 in activation of mitotic cyclin proteolysis will be characterized in detail. Two approaches will be taken to investigate the role of Cdks in repression of mitotic cyclin proteolysis during S phase and early mitosis. (1) Biochemical experiments will address whether Cdk phosphorylation directly inhibits the proteolysis process. (2) A genetic approach will identify genes required for repression of mitotic cyclin proteolysis during S phase and early mitosis. Uncontrolled cyclin expression can be lethal. It has been linked to cancerous transformation: cyclin overexpression is a prominent feature of certain tumors including breast cancer. Identifying and characterizing the regulatory networks, such as mitotic cyclin proteolysis, that restrict the activity of these proteins will open avenues towards the development of cancer diagnostics and therapeutics.