Coupled translation: a novel process for translation of two overlapping open reading frames in mRNA

翻译是生物学中最基本的过程的最后阶段，在这个过程中，生物体的遗传物质转化为蛋白质。在翻译过程中，核糖体（构建蛋白质的细胞机器）通过遵循一种称为mRNA的分子中编写的计划来制造新蛋白质。mRNA是一种单链分子，由4种不同的成分（称为核苷酸）组成，它们就像我们字母表中的字母一样组成代码。科学家们多年来一直在研究真核生物（高等生物）中核糖体机器的工作方式，并认为所有蛋白质都是以同样的方式产生的。病毒是一组微生物，它们感染其他生物并引起疾病。在感染过程中，它们必须利用被感染的细胞器官，包括核糖体来制造更多的新病毒。病毒不得不发展新的方法，以便在被感染的细胞摧毁它之前生存和繁殖得更快。这些新方法包括操纵细胞核糖体做有利于病毒的新事情。重要的是，病毒使用的所有新策略都必须与细胞的工作方式兼容。有趣的是，通过研究这些新策略，科学家们发现，不仅病毒使用它们，而且细胞也使用它们。我们正在研究一种名为RSV的病毒，大多数人可能在儿童时期感染过这种病毒，并且将来很有可能再次感染。RSV病毒还使用一种新的机制来表达一种名为M2-2的蛋白质。在这里，不是从一段mRNA中合成一种蛋白质，而是合成两种蛋白质。我们有兴趣弄清楚这是如何可能的。我们已经证明，为了制造第二种蛋白质：M2-2，必须制造第一种蛋白质M2-1。这意味着核糖体必须反向运动，因为第二种蛋白质的编码序列与第一种蛋白质的编码序列重叠。这是一个重要的发现，因为核糖体以前没有被证明具有这种能力。已经发现这段mRNA中的重要区域允许第二种蛋白质的产生。这些区域似乎存在于M2-1的编码序列中，这是令人惊讶的，因为在分子方面，这是一个很大的距离。如果我们通过引入突变来改变这些区域，那么第二种蛋白质的数量就会减少。在这个过程中很重要的一个区域已经被证明含有大量的二级结构。二级结构发生在mRNA分子不同部分的核苷酸可以相互作用的地方，这可以被认为是将两块拼图拼在一起。随着更多的部件被添加，结构变得更坚固。我们将进一步研究M2-1中的重要部分，以调查它们对M2-2生产的作用。要做到这一点，我们必须首先完成所有重要区域的位置映射。特别是我们专注于包含大量二级结构的区域。将在这些区域中引入不同类型的突变以确认其重要性。我们还希望更详细地研究制造第二种蛋白质M2-2的核糖体机器的组成部分。最后，我们希望我们可以解决mRNA分子的结构（完成拼图），以提供关于这种独特的蛋白质表达机制的更大图片。

Translation is the final stage of the most fundamental process in biology in which the genetic material of the organism is turned into proteins. During the process of translation; ribosomes (which are the cellular machines that build proteins) make the new protein by following a plan written in a molecule called mRNA. mRNA is a single stranded molecule made up from 4 different components (called nucleotides) which act like letters in our alphabet to make a code. Scientists have been studying the way the ribosome machine works in eukaryotes (higher organisms) for many years and thought that all proteins are made in the same way. Viruses are a group of microscopic organisms which infect and cause diseases in other organisms. During the infection process they must use the infected cells apparatus including ribosomes to make more new viruses. Viruses have been forced to develop new methods to survive and multiply faster before the infected cell can destroy it. These new methods include the manipulation of the cells ribosomes to do novel things which benefit the virus. Importantly, all new strategies used by the virus must be compatible with the workings of the cell to function. Interestingly, by studying these new strategies Scientists have seen that not only, do the viruses use them, but the cells also do. We are studying a virus called RSV which most individuals will have likely to have been infected with as a child and will have a good chance of being infected again in the future. The RSV virus also uses a novel mechanism to express a protein called M2-2. Here instead of just making one protein from a piece of mRNA two proteins are made. We are interested in working out how this is possible. We have shown that in order to make the second protein: M2-2 the first protein M2-1 must be made. This means the ribosomes must go in reverse as the coding sequence for the second protein overlaps with the coding sequence of the first. This was an important finding as ribosomes had not previously been shown to have this ability. Important regions within this piece of mRNA have been discovered that allow the second protein to be made. These regions appear to be present thought the coding sequence of M2-1 which is amazing because in molecular terms this is a large distance. If we change these regions by introducing mutations the amounts of the second protein made are reduced. One region which is important in this process has been shown to contain a lot of secondary structure. Secondary structure occurs where the nucleotides in different parts of the mRNA molecule can interact together, which can be thought of as like fitting two pieces of a jig-saw together. As more pieces are added the structure gets stronger. We will further characterise the important segments within M2-1 to investigate the role they have on M2-2 production. To do this we must first finish mapping the position of all of the important regions. In particular we focus on the region that contains a lot of secondary structure. Different types of mutations will be introduced in these regions to confirm there importance. We also hope to examine in more detail the components of the ribosome machine that make the second protein M2-2. Finally we hope that we can solve the structure (complete the jig-saw) of the mRNA molecule to provide a bigger picture on this unique mechanism of protein expression.