MOLECULAR MECHANISM OF MALARIA PATHOGENESIS: REGULATION OF TRANSCRIPTIONAL CONTRO

恶性疟原虫（Plasmodiumfalciparum）是一种复杂的生命周期，在蚊媒和人宿主中经历了不同的形态发育阶段。寄生虫的发育和分化与不同基因表达模式的表达相一致。为了了解寄生虫如何调节其基因表达，我们克隆了恶性疟原虫编码组蛋白脱乙酰酶（PfHDAC）的基因，PfHDAC是一种参与组蛋白修饰及其在染色质内相互作用的关键转录调节因子。 PfHDAC与哺乳动物组蛋白脱乙酰酶具有约50%的同源性。 而且，像大多数哺乳动物的酶一样，这种蛋白质主要在成熟寄生虫的细胞核中表达。 近年来研究发现，以哺乳动物组蛋白脱乙酰酶为靶点的药物对包括疟原虫在内的顶复门原虫具有抑制活性。 随着疟原虫抗药性的广泛存在，鉴定恶性疟原虫中的这种蛋白对于未来开发抗疟原虫的新疗法至关重要。 我们目前正在表达这种酶，用于进一步的生化表征和药物筛选。 由于该基因在寄生虫生命周期中的特异性表达，我们正在靶向该基因进行破坏，以使寄生虫减毒。通过与PfHDAC基因同源重组实现基因破坏以产生无效突变体。突变体寄生虫将进行生化、形态学和感染性表征。

Human malaria parasite, Plasmodium falciparum, has a complex life cycle, which involves the developemnt of various morphologically distinct stages in both mosquito vector and human host. Development and differentiation of the parasite coincides with expression of different pattern of gene expression. To understand how the parasite regulates its gene expression, we have cloned the P. falciparum gene encoding histone deacetylase (PfHDAC), a key transcription modulator involved in the modification of histone proteins and their interaction within chromatin. PfHDAC shows about 50% homology with mammalian histone deacetylases. And, like most of the mammalian enzymes, this protein is expressed mainly in the nucleus of mature parasites. Recently the drugs targeting mammalian histone deacetylases were shown to exhibit the inhibitory activity against apicomplexa protozoan including Plasmodium spp. With the widespread of drug resistance in malaria parasites, identification of this protein in P. falciparum is critical for the future development of novel therapeutics against malaria parasites. We're currently expressing this enzyme for further biochemical characterization and drug screening. Because of the specific expression of this gene during parasite life cycle, we are targeting this gene for disruption in order to make an attenauted a parasite. The gene disruption is being achieved by homologous recombination with PfHDAC gene to create a null mutant. The mutant parasites will be characterized biochemically, morphologically, and for infectivity.