RNA-guided assembly of Rev-RRE nuclear export complexes.
RNA-guided assembly of Rev-RRE nuclear export complexes.
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DOI：
10.7554/elife.03656
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发表时间：
2014-08-27
期刊：
影响因子：
7.7
通讯作者：
Doudna JA
中科院分区：
文献类型：
--
作者：
Bai Y;Tambe A;Zhou K;Doudna JA
HIV复制需要未剪接和单剪接病毒转录物的核输出。虽然已经提出了一个独特的RNA结构的Rev反应元件（RRE）负责病毒mRNA的输出，它如何招募多个HIV Rev蛋白形成一个出口复合物一直不清楚。我们在这里表明，Rev与RRE的初始结合触发RNA三级结构的变化，使进一步的Rev结合和病毒输出复合物的快速形成。使用SHAPE-Seq和小角X射线散射（SAXS）分析Rev-RRE组装途径揭示了Rev-RRE复合物形成的两个主要步骤，从快速Rev结合到呈现多个Rev结合位点的预组织区域开始。该步骤诱导RNA的长距离重塑以暴露隐藏的Rev结合位点，使得能够将额外的Rev蛋白快速组装到RNA输出复合物中。这种动力学途径可能有助于维持病毒复制和成熟之间的平衡。DOI：http://dx.doi.org/10.7554/eLife.03656.001 HIV是一种病毒，它会导致感染者的免疫系统逐渐衰竭，最终导致艾滋病。这种病毒由一个RNA分子组成，它编码病毒的遗传信息，并被蛋白质外壳包围。一旦艾滋病毒进入宿主细胞，其RNA基因组转化为DNA分子，DNA分子进入细胞核并成为宿主基因组的一部分。整合的病毒基因组可以在病毒开始复制之前保持休眠一段时间。HIV复制始于病毒基因组的RNA拷贝的产生。对于某些类型的病毒RNA分子要被翻译和包装成新的病毒颗粒，它们需要作为“核输出复合物”的一部分从细胞核输出。它由一个HIV RNA分子，一个称为Rev的HIV蛋白和两个宿主蛋白组成。核输出复合物的形成始于Rev蛋白的多个拷贝附着在病毒RNA的特定片段上，但Rev蛋白如何在RNA分子上组装以前尚不清楚。Bai等人现在已经使用结构和生物化学技术来剖析这一过程中的各个步骤。首先，Rev蛋白快速结合到RNA分子的预先形成的区域，其中多个结合位点是复杂组织的。这导致RNA的整体形状发生变化，并暴露出先前隐藏的Rev蛋白质的额外结合位点。然后，更多的Rev蛋白快速结合到新暴露的位点，最后两个宿主蛋白结合，整个复合物从细胞核中输出。Bai等人提出，在这两步组装过程中需要检查点以确保Rev蛋白特异性结合病毒RNA，并且这些检查点对于控制病毒复制可能是重要的。Bai等人的发现可能有助于开发通过阻断病毒从细胞核输出从而抑制HIV复制来治疗HIV感染的新药。DOI：http://dx.doi.org/10.7554/eLife.03656.002网站
HIV replication requires nuclear export of unspliced and singly spliced viral transcripts. Although a unique RNA structure has been proposed for the Rev-response element (RRE) responsible for viral mRNA export, how it recruits multiple HIV Rev proteins to form an export complex has been unclear. We show here that initial binding of Rev to the RRE triggers RNA tertiary structural changes, enabling further Rev binding and the rapid formation of a viral export complex. Analysis of the Rev-RRE assembly pathway using SHAPE-Seq and small-angle X-ray scattering (SAXS) reveals two major steps of Rev-RRE complex formation, beginning with rapid Rev binding to a pre-organized region presenting multiple Rev binding sites. This step induces long-range remodeling of the RNA to expose a cryptic Rev binding site, enabling rapid assembly of additional Rev proteins into the RNA export complex. This kinetic pathway may help maintain the balance between viral replication and maturation. DOI: http://dx.doi.org/10.7554/eLife.03656.001 HIV is a virus that causes the immune system of an infected person to gradually fail, which can eventually result in AIDS. The virus consists of an RNA molecule—which encodes its genetic information—surrounded by coats of proteins. Once HIV enters a host cell, its RNA genome is converted into a DNA molecule, which travels to the nucleus and becomes part of the host's genome. The integrated viral genome can remain dormant for an extended period before the virus starts to replicate. HIV replication begins with the production of RNA copies of the viral genome. For certain types of viral RNA molecules to be translated and packaged into new virus particles they need to be exported from the nucleus as part of the ‘nuclear–export complex’. This is made up of: a HIV RNA molecule, a HIV protein called Rev, and two host proteins. Formation of the nuclear–export complex begins with multiple copies of the Rev protein attaching to specific stretches of the viral RNA, but how the Rev proteins assemble on the RNA molecule was previously unclear. Bai et al. have now used both structural and biochemical techniques to dissect the individual steps in this process. First, Rev proteins rapidly bind to a pre-formed region of the RNA molecule where multiple binding sites are compactly organized. This causes the overall shape of the RNA to change, and exposes a previously hidden extra binding site for Rev proteins. More Rev proteins then quickly bind to the newly exposed site, before finally the two host proteins bind and the whole complex is exported from the nucleus. Bai et al. propose that checkpoints during this two-step assembly process are required to ensure that Rev proteins specifically bind to viral RNAs, and that such checkpoints may be important for controlling viral replication. The findings of Bai et al. may, in future, help to develop new drugs that treat HIV infection by blocking the export of the virus from the nucleus and thus inhibiting HIV replication. DOI: http://dx.doi.org/10.7554/eLife.03656.002