Achieving a Golden Mean: Mechanisms by Which Coronaviruses Ensure Synthesis of the Correct Stoichiometric Ratios of Viral Proteins
Achieving a Golden Mean: Mechanisms by Which Coronaviruses Ensure Synthesis of the Correct Stoichiometric Ratios of Viral Proteins
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DOI：
10.1128/jvi.02480-09
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发表时间：
2010-05-01
影响因子：
5.4
通讯作者：
Dinman, Jonathan D.
中科院分区：
文献类型：
--
作者：
Plant, Ewan P.;Rakauskaite, Rasa;Dinman, Jonathan D.
在逆转录病毒和双链RNA Totiviruses中，程序性-1核糖体移码的效率对于确保上游编码的衣壳蛋白与下游编码的复制酶的适当比例至关重要。许多其他移码病毒（包括冠状病毒）的基因组结构非常不同，因为它们的上游开放阅读框编码非结构蛋白，移码依赖性下游开放阅读框编码参与转录和复制的酶，而它们的结构蛋白由亚基因组mRNA编码。移码效率的生物学意义以及由上游和下游开放阅读框编码的蛋白质的相对比率如何影响病毒繁殖以前尚未被探索。在这里，采用了三种不同的策略来测试以下假设：冠状病毒的-1PRF信号已经进化以产生上游与下游编码蛋白质的正确比例。具体而言，严重急性呼吸综合征（SARS）相关冠状病毒的感染性克隆携带降低移码效率的突变，使感染性降低>4个数量级。第二，一系列的移码促进mRNA假结突变体被用来证明，移码信号的SARS相关冠状病毒和小鼠肝炎病毒已经发展到促进最佳移码效率。最后，我们表明，先前描述的移码衰减元件实际上并不影响移码本身，而是用来限制核糖体的分数可用于移码。这些分析的结果都支持一个“黄金分割”模型，即病毒使用程序化的核糖体移码和翻译衰减来控制其编码蛋白的相对比例。
In retroviruses and the double-stranded RNA totiviruses, the efficiency of programmed -1 ribosomal frameshifting is critical for ensuring the proper ratios of upstream-encoded capsid proteins to downstreamencoded replicase enzymes. The genomic organizations of many other frameshifting viruses, including the coronaviruses, are very different, in that their upstream open reading frames encode nonstructural proteins, the frameshift-dependent downstream open reading frames encode enzymes involved in transcription and replication, and their structural proteins are encoded by subgenomic mRNAs. The biological significance of frameshifting efficiency and how the relative ratios of proteins encoded by the upstream and downstream open reading frames affect virus propagation has not been explored before. Here, three different strategies were employed to test the hypothesis that the -1 PRF signals of coronaviruses have evolved to produce the correct ratios of upstream-to downstream-encoded proteins. Specifically, infectious clones of the severe acute respiratory syndrome (SARS)-associated coronavirus harboring mutations that lower frameshift efficiency decreased infectivity by >4 orders of magnitude. Second, a series of frameshift-promoting mRNA pseudoknot mutants was employed to demonstrate that the frameshift signals of the SARS-associated coronavirus and mouse hepatitis virus have evolved to promote optimal frameshift efficiencies. Finally, we show that a previously described frameshift attenuator element does not actually affect frameshifting per se but rather serves to limit the fraction of ribosomes available for frameshifting. The findings of these analyses all support a "golden mean" model in which viruses use both programmed ribosomal frameshifting and translational attenuation to control the relative ratios of their encoded proteins.