CELL CYCLE OF PLASMODIUM FALCIPARUM

恶性疟原虫是人类疟疾的病原体，在蚊子和人类宿主的生命周期中经历了明显的形态变化。在红细胞内的生命周期中，寄生虫与真核细胞周期的模式不同，经历了多轮DNA复制，从一个细胞形成8到32个分裂子。对调节疟原虫异常红细胞发育阶段的生化变化和分子开关的清晰理解尚未建立。本研究的长期目标是在疟原虫恶性疟原虫的红细胞内发育阶段建立细胞周期调节模型。恶性疟原虫发育过程中DNA合成起始的精确时间调控以及S期和有丝分裂之间的关系尚不清楚，参与细胞周期进程的蛋白质的身份及其调控方式也不清楚。我们实验室最近的研究已经确定了一些分子工具，以启动恶性疟原虫细胞周期调控的深入研究。具体来说，我们建议进行以下工作：(a)为了鉴定和表征恶性疟原虫复制前复合体的成分，我们将首先关注恶性疟原虫MCM4、ORC1和ORC5同源物在细胞周期调节下的表达、细胞内定位和磷酸化的变化。(b)通过基于噬菌体的相互作用克隆、lambda筛选库的磷酸化筛选和双杂交筛选，鉴定与恶性疟原虫CDK样激酶、CDK活化激酶和复制前复合物组分相互作用的蛋白。(c)发展更有效的寄生虫细胞周期同步方法。恶性疟原虫细胞周期调控因子的详细分析提供了洞察在疟原虫分裂过程中不寻常的无性分裂的分子机制。此外，参与细胞周期进程的酶有可能成为药物开发的有吸引力的靶点，特别是考虑到寄生虫和宿主细胞周期调节的差异可能允许在指导针对寄生虫的治疗时具有一定程度的特异性。

Plasmodium falciparum, the causative agent of human malaria, undergoes distinct morphological changes during the progression through its life cycle in the mosquito and human hosts. During the intraerythrocytic life cycle, the parasite diverges from the paradigm of eukaryotic cell cycle by undergoing multiple rounds of DNA replication and forms 8 to 32 merozoites from a single cell. A clear understanding of the biochemical changes and molecular switches that regulate the unusual erythrocytic developmental stages of the malaria parasite has not been established. The long-term goal of this research is to develop a model for cell cycle regulation in the intraerythrocytic stages of development of malaria parasite P. falciparum. The regulation of the precise timing of initiation of DNA synthesis and the relationship between S phase and mitosis during development in P. falciparum remains unclear, as does the identity of the proteins involved in cell cycle progression and how the are regulated. Recent research done in our laboratory has identified a few molecular tools to initiate an in-depth study of the cell cycle regulation of P. falciparum. Specifically, we propose to carry out the following: (a) To identify and characterize components of P. falciparum pre-replication complex, we will initially focus on cell cycle regulated changes in expression, intracellular localization, and phosphorylation of P. falciparum homologues of MCM4, ORC1 and ORC5. (b) Identify proteins interacting with P. falciparum CDK-like kinases, CDK- activating kinases and pre-replication complex components by phage- based interaction cloning, phosphorylation screen of a lambda screen library, and by two-hybrid screen. (c) Develop more effective means of cell cycle synchronization of the parasites. A detailed analysis of P. falciparum cell cycle regulators provide insight into the molecular mechanism of unusual asexual division during Plasmodium schizogony. Furthermore, enzymes involved in cell cycle progression have the potential to be attractive targets for drug development, especially given that differences between cell cycle regulation in parasite and host might permit a level of specificity in directing therapies against the parasite.