Mechanisms of protein production in the parasite Giardia Iamblia

摘要 蓝氏贾第鞭毛虫是一种单细胞原生生物，其对人类的寄生感染对健康构成重大威胁。 全世界。治疗是有限的，而且疗效各不相同：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，甚至在经过处理的水中也发生了疫情 消息来源。尽管贾第鞭毛虫的基本分子生物学与传统模型系统相似，但它是 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 基本上是这样的。贾第虫和它的宿主之间的根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 机会还没有被利用。特别是，贾第虫如何启动蛋白质的许多方面 生产似乎不同于在传统模型系统中所研究的东西，但目前 这些差异的机制含义仍然是个谜。贾第虫的mRNAs非常短 未翻译的区域，它们的核糖体似乎不能扫描，我们的分析表明它们缺乏一些 在真核生物中几乎普遍存在的核心启动因子。这些结果表明 引发机制的差异，我们将通过生化和结构来探索 接近。我们建议通过对基本特征的初步探索来部分解决这一差距 贾第虫的蛋白质合成机制。我们将利用我们的能力培养和遗传 操纵贾迪亚，结合我们在翻译启动和结构机制研究方面的专业知识 生物学。我们将追求两个目标：(1)解决贾第虫核糖体的结构和它的 用低温电子显微镜观察亚基。初步分析显示，在这些方面存在意想不到的差异 核糖体与其他真核生物的比较；观察这些差异的构象含义将 为详细的机制研究提供必要的基础，并可能提出治疗靶点。(2) 我们将研究贾第虫翻译起始复合体的组成和结构。 总体而言，这些探索性研究有望产生与基本分子机制相关的发现。 被贾第虫用来产生蛋白质，为未来的研究奠定了基础，这些研究将更广泛和 深入探讨贾第鞭毛虫的基因调控机制。

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.