Viral Recombination Section, HIV Drug Resistance Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA.
J Virol. 2014 Apr;88(8):4040-6. doi: 10.1128/JVI.03745-13. Epub 2014 Jan 22.
A key step of retroviral replication is packaging of the viral RNA genome during virus assembly. Specific packaging is mediated by interactions between the viral protein Gag and elements in the viral RNA genome. In HIV-1, similar to most retroviruses, the packaging signal is located within the 5' untranslated region and extends into the gag-coding region. A recent study reported that a region including the Gag-Pol ribosomal frameshift signal plays an important role in HIV-1 RNA packaging; deletions or mutations that affect the RNA structure of this signal lead to drastic decreases (10- to 50-fold) in viral RNA packaging and virus titer. We examined here the role of the ribosomal frameshift signal in HIV-1 RNA packaging by studying the RNA packaging and virus titer in the context of proviruses. Three mutants with altered ribosomal frameshift signal, either through direct deletion of the signal, mutation of the 6U slippery sequence, or alterations of the secondary structure were examined. We found that RNAs from all three mutants were packaged efficiently, and they generate titers similar to that of a virus containing the wild-type ribosomal frameshift signal. We conclude that although the ribosomal frameshift signal plays an important role in regulating the replication cycle, this RNA element is not directly involved in regulating RNA encapsidation.
To generate infectious viruses, HIV-1 must package viral RNA genome during virus assembly. The specific HIV-1 genome packaging is mediated by interactions between the structural protein Gag and elements near the 5' end of the viral RNA known as packaging signal. In this study, we examined whether the Gag-Pol ribosomal frameshift signal is important for HIV-1 RNA packaging as recently reported. Our results demonstrated that when Gag/Gag-Pol is supplied in trans, none of the tested ribosomal frameshift signal mutants has defects in RNA packaging or virus titer. These studies provide important information on how HIV-1 regulates its genome packaging and generate infectious viruses necessary for transmission to new hosts.
逆转录病毒复制的关键步骤是在病毒组装过程中包装病毒 RNA 基因组。特定的包装是由病毒蛋白 Gag 与病毒 RNA 基因组中元件之间的相互作用介导的。在 HIV-1 中，与大多数逆转录病毒类似，包装信号位于 5'非翻译区，并延伸到 gag 编码区。最近的一项研究报告称，包括 Gag-Pol 核糖体移码信号在内的一个区域在 HIV-1 RNA 包装中起着重要作用；影响该信号 RNA 结构的缺失或突变会导致病毒 RNA 包装和病毒滴度急剧下降（10-50 倍）。我们通过研究前病毒中的 RNA 包装和病毒滴度，研究了核糖体移码信号在 HIV-1 RNA 包装中的作用。通过直接删除信号、突变 6U 滑序列或改变二级结构，研究了三种改变核糖体移码信号的突变体。我们发现，所有三种突变体的 RNA 都能有效地包装，它们产生的滴度与含有野生型核糖体移码信号的病毒相似。我们得出结论，尽管核糖体移码信号在调节复制周期中起着重要作用，但该 RNA 元件并不直接参与调节 RNA 封装。
为了产生感染性病毒，HIV-1 必须在病毒组装过程中包装病毒 RNA 基因组。特定的 HIV-1 基因组包装是由结构蛋白 Gag 与病毒 RNA 近 5' 端的称为包装信号的元件之间的相互作用介导的。在这项研究中，我们检查了最近报道的 Gag-Pol 核糖体移码信号是否对 HIV-1 RNA 包装很重要。我们的结果表明，当 Gag/Gag-Pol 以转染方式提供时，测试的核糖体移码信号突变体在 RNA 包装或病毒滴度方面均无缺陷。这些研究提供了关于 HIV-1 如何调节其基因组包装并产生感染性病毒以传播给新宿主的重要信息。
