CELL CYCLE OF PLASMODIUM FALCIPARUM

恶性疟原虫（Plasmodium falciparum）是人类疟疾的病原体，其在蚊子和人类宿主中的生命周期过程中经历不同的形态学变化。在红细胞内的生命周期中，寄生虫通过经历多轮DNA复制而偏离真核细胞周期的范例，并从单个细胞形成8至32个裂殖子。对调节疟原虫不寻常的红细胞发育阶段的生物化学变化和分子开关的清楚理解尚未建立。本研究的长期目标是建立恶性疟原虫红细胞内发育阶段细胞周期调控的模型。在恶性疟原虫发育过程中，DNA合成起始的精确时间的调节以及S期和有丝分裂之间的关系仍然不清楚，参与细胞周期进程的蛋白质的身份以及如何调节也不清楚。我们实验室最近的研究已经确定了一些分子工具，以启动对恶性疟原虫细胞周期调控的深入研究。具体而言，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物的组分，我们将首先关注恶性疟原虫同源物MCM4、ORC1和ORC5的表达、细胞内定位和磷酸化的细胞周期调节变化。(b)通过基于噬菌体的相互作用克隆、λ筛选文库的磷酸化筛选和通过双杂交筛选来鉴定与恶性疟原虫CDK样激酶、CDK激活激酶和复制前复合物组分相互作用的蛋白质。(c)开发更有效的寄生虫细胞周期同步化手段。对恶性疟原虫细胞周期调节因子的详细分析为了解疟原虫无性生殖过程中不寻常的无性分裂的分子机制提供了线索。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控之间的差异可能允许针对寄生虫的治疗具有一定的特异性。

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.