Mechanisms of protein production in the parasite Giardia Iamblia

总结 蓝氏贾第鞭毛虫是一种单细胞原生生物，其寄生虫感染人类对健康构成重大威胁 国际吧治疗方法有限且疗效不一：在发展中国家，贾第虫感染可能导致 严重的疾病和死亡，而在发达国家，甚至从处理过的水也发生了疫情 源虽然贾第虫的基本分子生物学与传统的模型系统相似， 也是一种分支很深的真核生物，其基因调控机制的许多方面都存在分歧， 实质上。贾第虫和宿主之间的基本分子差异提供了一个机会 进行治疗干预。然而，人们对这些差异知之甚少，因此这种治疗方法 机会尚未被利用。特别是，贾第虫如何启动蛋白质 生产似乎与传统模型系统中研究的不同，但目前， 这些差异的机械含义仍然是神秘的。贾第虫的mRNAs非常短， 在非翻译区，它们的核糖体似乎不扫描，我们的分析表明，它们缺乏一些 的核心起始因子几乎普遍存在于真核生物。这些结果表明， 在启动机制的差异，我们将通过一个生物化学和结构探索 approach.我们建议通过初步探索的基本特征， 贾第虫的蛋白质合成机制我们将利用我们的文化和遗传能力 操纵贾第虫，结合我们在翻译起始和结构的机制研究方面的专业知识， 生物学我们将追求两个目标：（1）我们将解决贾第虫核糖体的结构和它的 亚基的冷冻电镜观察。初步分析显示，这些差异出乎意料 核糖体与其他真核生物相比;观察这些差异的构象含义将 为详细的机制研究提供了必要的基础，并可能提出治疗靶点。（二） 我们将研究贾第虫翻译起始复合物的组成和结构。 总的来说，这些探索性研究有望产生与基本分子机制相关的发现 贾第虫用来产生蛋白质，为未来的研究奠定了基础， 深入探究贾第虫的基因调控机制。

SUMMARY Giardia lamblia is a unicellular protist whose parasitic infections of humans is a significant threat to health worldwide. Treatments are limited and of variable efficacy: in the developing world Giardia infection can lead to severe disease and death, while in the developed world outbreaks have occurred even from treated water sources. Although the basic molecular biology in Giardia is similar to that in traditional model systems, it is also a deeply branching eukaryote, and so many aspects of its gene regulatory mechanisms have diverged substantially. The fundamental molecular differences between Giardia and its hosts present an opportunity for therapeutic intervention. However, little is understood about these differences, and thus this treatment opportunity has not yet been exploited. In particular, many aspects of how Giardia initiates protein production seem different from what has been studied in traditional model systems, but, currently, the mechanistic implications of these differences remains mysterious. Giardia mRNAs have remarkably short untranslated regions, their ribosomes do not appear to scan, and our analysis suggests that they lack some of the core initiation factors shared almost universally in eukaryotes. These results suggest fundamental differences in the mechanism of initiation, which we will explore through a biochemical and structural approach. We propose to partially address this gap through an initial exploration of fundamental features of the protein synthesis machinery of Giardia. We will take advantage of our ability to culture and genetically manipulate Giardia, combined with our expertise in mechanistic studies of translation initiation and structural biology. We will pursue two aims: (1) We will solve the structure of the Giardia ribosome and its subunits using cryo-electron microscopy. Preliminary analysis shows unexpected differences in these ribosomes compared to other eukaryotes; observing the conformational implications of these differences will provide an essential foundation for detailed mechanistic studies and could suggest therapeutic targets. (2) We will investigate the composition and architecture of Giardia translation initiation complexes. Overall, these exploratory studies promise to yield discoveries related to the basic molecular machinery used by Giardia to generate protein, laying the foundation for future studies that will more broadly and deeply interrogate gene regulation mechanisms in Giardia.