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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Evidence that viral RNAs have evolved for efficient two-stage packaging
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Evidence that viral RNAs have evolved for efficient two-stage packaging

机译：病毒RNA已经进化为有效的两阶段包装的证据

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摘要

Genome packaging is an essential step in virus replication and a potential drug target. Single-stranded RNA viruses have been thought to encapsidate their genomes by gradual co-assembly with capsid subunits. In contrast, using a single molecule fluorescence assay to monitor RNA conformation and virus assembly in real time, with two viruses from differing structural families, we have discovered that packaging is a two-stage process. Initially, the genomic RNAs undergo rapid and dramatic (approximately 20-30%) collapse of their solution conformations upon addition of cognate coat proteins. The collapse occurs with a substoichio-metric ratio of coat protein subunits and is followed by a gradual increase in particle size, consistent with the recruitment of additional subunits to complete a growing capsid. Equivalently sized nonviral RNAs, including high copy potential in vivo competitor mRNAs, do not collapse. They do support particle assembly, however, but yield many aberrant structures in contrast to viral RNAs that make only capsids of the correct size. The collapse is specific to viral RNA fragments, implying that it depends on a series of specific RNA-protein interactions. For bacteriophage MS2, we have shown that collapse is driven by subsequent protein-protein interactions, consistent with the RNA-protein contacts occurring in defined spatial locations. Conformational collapse appears to be a distinct feature of viral RNA that has evolved to facilitate assembly. Aspects of this process mimic those seen in ribosome assembly.
机译：基因组包装是病毒复制中必不可少的步骤，也是潜在的药物靶标。人们认为单链RNA病毒通过与衣壳亚基逐渐共组装而使其基因组封闭。相反，使用单分子荧光测定法实时监测RNA构象和病毒装配，并使用来自不同结构家族的两种病毒，我们发现包装是一个两阶段的过程。最初，在添加同源外壳蛋白后，基因组RNA的溶液构象迅速而剧烈地（大约20％至30％）崩溃。塌陷发生在外壳蛋白亚基的亚化学计量比下，随后粒径逐渐增加，这与补充其他亚基以完成衣壳生长有关。等效大小的非病毒RNA（包括具有高复制潜力的体内竞争者mRNA）不会崩溃。它们确实支持颗粒装配，但是与仅构成正确大小衣壳的病毒RNA相比，会产生许多异常结构。崩溃是病毒RNA片段特有的，这意味着它取决于一系列特定的RNA-蛋白质相互作用。对于噬菌体MS2，我们已经表明崩溃是由随后的蛋白质-蛋白质相互作用驱动的，这与在确定的空间位置发生的RNA-蛋白质接触一致。构象性崩溃似乎是病毒RNA的一个显着特征，它已经进化为促进装配。该过程的各个方面模仿了核糖体装配中看到的那些。

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