Understanding the reprogramming of host mRNA translation during calicivirus infection

我们的总体目标是了解一组特征不佳但却很重要的病毒调节宿主基因表达的机制，以调节细胞如何响应病毒感染体内的细胞以多种方式响应环境刺激和病原体感染，其中最常见的是通过调节细胞基因表达。储存在我们基因中的信息的表达在许多水平上受到严格控制，以确保在正确的时间和数量产生正确的蛋白质。首先，通过一个称为转录的过程，我们DNA中编码的遗传信息被转化为信使RNA(信使RNA)。然后，被称为核糖体的结构在称为起始因子的蛋白质的辅助下，将信使核糖核酸“翻译”成蛋白质。EIF4E就是这些蛋白质中的一种，它的关键作用是将核糖体和其他蛋白质定向到mRNA上。这个过程被称为翻译，合成的蛋白质决定了我们的细胞是什么，定义了它们的属性和功能。重要的是，细胞中蛋白质的变化也有助于对抗病毒等入侵的病原体。虽然病毒可以感染大多数生物体并造成严重损害，但它们主要由包裹在蛋白质外壳中的RNA或DNA组成，缺乏复制和传播所需的因素。因此，它们依赖宿主细胞资源来产生病毒蛋白。因此，许多病毒已经开发出调节宿主蛋白质合成机制功能的策略，通常导致病毒mRNAs的优先翻译。杯状病毒是一类可引起人类和动物疾病的小病毒家族。在人类中，它们主要导致胃肠炎。人类诺沃克病毒是一种杯状病毒，在细胞培养中不能很好地生长，而老鼠诺沃克病毒是一种小鼠同源物，可以作为实验室研究杯状病毒生物学许多方面的模型。它是剖析病毒如何影响宿主细胞蛋白质翻译的一个极好的模型。使用这个模型，我们以前已经在理解杯状病毒如何产生病毒蛋白方面取得了一些重大进展。我们发现，一种名为VPG的病毒编码蛋白对于病毒mRNA的翻译是必不可少的，因为它协调宿主蛋白向病毒RNA的招募。我们还发现杯状病毒感染调节了宿主翻译机制的组成和活性。然而，我们仍然对病原体，特别是杯状病毒在感染过程中如何调控宿主mRNAs的翻译知之甚少。这一点很重要，因为了解病毒对特定宿主mRNA翻译的调节可以揭示病毒如何操纵有机体对感染的反应。我们的假设是杯状病毒改变受感染宿主中特定mRNAs的翻译，以调节抗病毒基因的表达，并且它们通过调节翻译因子eIF4E来做到这一点。因此，我们的目标是使用高通量测序和生化方法1-表征病毒感染如何改变受感染宿主翻译的mRNA2-了解在这一过程中杯状病毒如何调节eIF4E的活性。如果我们能够充分了解杯状病毒是如何控制翻译因子的活性并重新编程宿主蛋白质合成的，我们就可以找到抑制病毒复制的方法。因此，我们的工作将有助于开发针对这一重要病毒组的新型抗病毒疗法，或许还包括其他调节翻译的病毒。了解基因调控的基本机制不仅对病毒学家，而且对更广泛的学术界都很重要。通过提高我们对翻译控制的基础知识，我们可能会更好地理解与eIF4E活动调节有关的几种病理机制，如癌症和糖尿病。

Our overarching aim is to understand the mechanism by which a group of poorly characterised, yet important viruses, regulate host gene expression to modulate how cells respond to viral infection Cells within the body respond to environmental stimuli and pathogen infection in many ways, the most common of which is via the regulation of cellular gene expression. The expression of the information stored in our genes is tightly controlled at numerous levels, to ensure that the correct protein is produced at the right time and quantity. First, the genetic information encoded in our DNA is converted into messenger RNA (mRNA), via a process called transcription. The mRNA is then "translated" into proteins by structures referred to as ribosomes, assisted by proteins called initiation factors. eIF4E is one of these proteins and its key role is to direct the ribosomes and other proteins to the mRNA. This process is called translation and the synthesised proteins make our cells what they are, defining their properties and functions. Importantly, changes to the proteins in our cells also help to fight against invading pathogens such as viruses. While viruses can infect most organisms and cause severe damage, they consist primarily of RNA or DNA enclosed in a protein coat and lack the factors required for replication and dissemination. They are therefore dependent on the host cell resources to produce viral proteins. Thus, many viruses have developed strategies that regulate the function of the host protein synthesis machinery, often leading to preferentially translation of viral mRNAs. Caliciviruses are a family of small viruses that can cause diseases both in humans and animals. In humans they primarily cause gastroenteritis. While the human norovirus, a calicivirus, does not grow well in cell culture, murine norovirus, a mouse homologue, acts as model with which to study many aspects of calicivirus biology in the laboratory. It represents an excellent model to dissect how viruses affect the translation of host cell proteins. Using this model we have previously made a number of significant advances in the understanding of how the caliciviruses produce viral proteins. We found that a virus-encoded protein, called VPg, is essential for the translation of viral mRNA as it coordinates the recruitment of host proteins to the viral RNA. We also showed that calicivirus infection modulates the composition and activity of the host translation machinery. However, we still know very little about how pathogens in general, and caliciviruses in particular, modulate the translation of host mRNAs during infection. This is important because understanding the modulation of specific host mRNA translation by viruses can reveal how viruses manipulate the organism's response to infection. Our hypothesis is that caliciviruses alter the translation of specific mRNAs in the infected host to regulate antiviral gene expression, and that they do so by modulating the translation factor eIF4E. Therefore, our objectives are to use high-throughput sequencing and biochemical methods to 1- characterize how the viral infection alters the profile of mRNAs that are translated by the infected host and 2- to understand how the activity of eIF4E is regulated by caliciviruses during this process. If we can fully understand how caliciviruses control the activity of translation factors and reprogramme the host protein synthesis, we can identify ways to inhibit virus replication. Therefore, our work will aid in the development of novel antiviral therapies for this important group of viruses, and perhaps other viruses that regulate translation. Understanding the fundamental mechanisms of gene regulation is important not only for virologists but also for broader academic communities. By advancing our basic knowledge of translational control we may understand better several pathologies that are linked to modulation of eIF4E activity, such as cancer and diabetes.