Plasmodium Recombination of Machinery

疟疾寄生虫，全世界负责3亿至5亿新感染和1-2百万人死亡 年然而，一种有效的疫苗仍然难以捉摸，部分原因是抗原多样性和免疫缺陷。 寄生虫的逃避策略免疫机制与抗原变异密切相关， 这一现象对于疫苗的研制具有极其重要的意义， 寄生虫拟议研究的长期目标是研究遗传学的机制， 与抗原变异等现象相关的重排。这项工作的基本原则 提出的是，了解疟原虫中的重组机制将提供改进的 为治疗的发展提供了机会。在其他真核生物中，同源重组（HR） 在染色体重排中起主要作用，而Rad 51和Dmc 1蛋白，真核生物的对应物， 是有丝分裂和减数分裂过程中参与HR的中心分子。在 在真核生物中，另外的蛋白质如RPA和Rad 54在功能上与Rad 51合作并介导HR， 修复受损的染色体所提出的研究的假设是，Rad 51和 其他相互作用的蛋白质，作为HR的介质，在生长和发育过程中起着关键作用。 寄生虫和促进基因重排的恶性疟原虫。Rad 51和Dmc 1的分子鉴定 恶性疟原虫中的同源物和重组PfRad 51的酶性质的最新表征， 例如DNA链交换和ATP酶活性，已经强烈地表明了保守功能作用 PfRad 51在这些生物体中。我们将用生物化学和遗传学来检验我们的假设 方法。具体目标1-3中的研究将导致涉及以下的蛋白质的体外表征： 从而探讨寄生虫重组和基因重排的生化基础。 在特定目标4中PfRad 51过表达和基因敲除研究将直接评估 PfRad 51在疟原虫红细胞生长中的作用及var基因转录谱分析 此外，对Dmc 1破坏的研究（具体目的4）将评估减数分裂特异性重组酶的作用 在疟疾传播过程中。这项研究的结果应该是重要的，在解开重组 机制和分子和遗传基础的重组和遗传重排的恶性疟原虫。

Malaria parasites, worldwide are responsible for 300-500 million new infections and 1-2 million deaths each year. An effective vaccine, however, remains elusive, partly due to antigenic diversity and the immune evasion strategies of the parasite. Recombination mechanisms are intimately linked with antigenic variation, a phenomenon of utmost significance for vaccine development against protozoan parasites like the malaria parasite. The long term objective of the proposed studies is to investigate mechanism(s) of genetic rearrangements associated with phenomenon like antigenic variation. An underlying tenet of the work proposed is that understanding the recombination mechanisms in Plasmodium will provide improved opportunities for the development of therapies. In other eukaryotes, homologous recombination (HR) plays a major role in chromosomal rearrangements, and Rad51 and Dmc1 proteins, the eukaryotic counterparts of bacterial RecA recombinase, are central molecules involved in HR during mitosis and meiosis. In eukaryotes, additional proteins like RPA and Rad54 functionally cooperate with Rad51 and mediate HR and the repair of damaged chromosomes. The hypothesis underlying proposed studies is that the Rad51 and other interacting proteins, as mediators of HR, play critical role(s) during growth and development of the parasite and facilitate gene rearrangements in P. falciparum. Molecular identification of Rad51 and Dmc1 homologues in P. falciparum and recent characterization of enzymatic properties of recombinant PfRad51, such as DNA strand exchange and ATPase activities, have strongly indicated a conserved functional role for PfRad51 in these organisms. We will test our hypothesis using biochemical as well as genetic approaches. Studies in the specific aims 1-3 will lead to in vitro characterization of the proteins involved in HR and thus probe into the biochemical basis of recombination and gene rearrangements in the parasites. PfRad51 over-expression and gene knockout studies in specific aim 4 will directly evaluate importance of PfRad51 in the erythrocytic growth of the parasite and analysis of repertoire of var gene transcripts. Moreover, studies on Dmc1 disruption (specific aim 4) will evaluate the role of meiosis specific recombinase during malaria transmission. The results of this study should be important in unraveling the recombination machinery and molecular and genetic basis for recombination and genetic rearrangements in P. falciparum.