Regulation of cell cycle transition by a cyclin-dependent kinase in trypanosomes

细胞周期蛋白依赖性激酶（CDKs）是真核生物细胞周期的基本调节因子， 通过与细胞周期蛋白结合而被激活，细胞周期蛋白的丰度在细胞周期中发生变化。单个细胞周期蛋白和多个 CDK在酵母细胞周期控制中起作用，而多种细胞周期蛋白和多种CDK控制细胞周期 动物的进步锥虫似乎采用一种细胞周期控制系统， 从真菌和动物中分离出来。PHO 80样细胞周期蛋白CYC 2和CDK相关激酶CRK 1控制G1/S G2/M转换由B型细胞周期蛋白CYC 6和另一种CDK相关激酶CRK 3控制。 然而，CRK 1如何发挥其在细胞周期进程中的作用仍然是难以捉摸的，主要是因为其下游 目标不明。目前的建议旨在了解G1/S细胞的机制 细胞周期转换和不同生命周期形式之间的不同细胞周期调节的分子基础， T.布鲁塞。在本计划的目标1中，我们计划应用化学遗传学方法来鉴定CRK 1底物 从前循环和血流形式，并比较分析CRK 1调节的细胞通路 两种形式之间。目的二是了解细胞周期依赖蛋白的作用机制 翻译起始，重点是CRK 1对两个翻译起始因子的调控。目标3是 通过研究CRK 1介导的DNA复制调控，剖析CRK 1在DNA复制起始中的作用 Cdc 45-Mcm 2 -7-GINS复合物中的复制因子。通过分子、细胞生物学、化学遗传学， 和生物化学方法，我们在这个建议中的总体目标是了解CRK 1的机制作用 通过调节DNA复制解旋酶参与G1/S调控，并参与G1特异性蛋白质翻译 通过调控翻译起始因子来启动。这些研究的结果不仅将 显著推进我们对锥虫细胞周期转换机制的理解，但也 可以验证CRK 1及其锥虫特异性下游途径作为抗锥虫的药物靶点 化疗

Cyclin-dependent kinases (CDKs) are the fundamental regulators of the cell cycle in eukaryotes, which are activated by binding to cyclins whose abundance changes during the cell cycle. A single cyclin and multiple CDKs function in yeast cell cycle control, whereas multiple cyclins and multiple CDKs control the cell cycle progression in animals. Trypanosomes appear to employ a cell cycle control system that is strikingly different from that in fungi and animals. A PHO80-like cyclin, CYC2, and a CDK-related kinase, CRK1, control the G1/S transition, whereas a B-type cyclin, CYC6, and another CDK-related kinase, CRK3, govern the G2/M transition. However, how CRK1 exert their roles in cell cycle progression remains elusive, mainly because its downstream targets are not known. The current proposal aims to understand the mechanisms underlying the G1/S cell cycle transition and the molecular basis for the distinct cell cycle regulation between different life cycle forms of T. brucei. In aim 1 of this proposal, we plan to apply chemical genetic approach to identify CRK1 substrates from the procyclic and bloodstream forms and to comparatively analyze the CRK1-regulated cellular pathways between the two forms. Aim 2 is to understand the mechanisms underlying the cell cycle-dependent protein translation initiation, with a focus on the regulation of two translation initiation factors by CRK1. Aim 3 is to dissect the role of CRK1 in DNA replication initiation by investigating CRK1-mediated regulation of the DNA replication factors in the Cdc45-Mcm2-7-GINS complex. Through molecular, cell biological, chemical genetic, and biochemical approaches, our overall goal in this proposal is to understand the mechanistic roles of CRK1 in the G1/S control through regulating the DNA replicative helicase and in G1-specific protein translation initiation through regulating translation initiation factors. The outcomes from these studies not only will significantly advance our understanding of the mechanisms of cell cycle transitions in trypanosomes, but also could validate CRK1 and its trypanosome-specific downstream pathways as drug targets for anti-trypanosome chemotherapy.