Regulation of Retroviral RNA Packaging and Dynamics of HIV-1 RNA Export

全长HIV-1 RNA需要从细胞核中输出以执行其功能，包括作为Gag/Gag- pol翻译的模板和作为新组装的病毒粒子的基因组。为了研究HIV-1 RNA包装，我们开发了一种新的检测方法，以单RNA分子灵敏度直接观察颗粒中的病毒RNA。这一分析表明，大多数HIV-1颗粒含有病毒RNA。虽然已知包装成颗粒的逆转录病毒RNA是二聚体，但标准的生化分析不能确定一个颗粒中RNA分子的数量；我们的结果为长期以来的假设提供了证据，即两个RNA分子（一个二聚体）被包装成一个粒子。为了更好地理解RNA包装的机制，我们进行了遗传、生化和成像分析，表明HIV-1 RNA使用DIS序列的碱基配对来选择其共包装的RNA伴侣，这一过程在RNA包装成颗粒之前发生在产生细胞的细胞质中。我们和其他人已经观察到，HIV-1 RNA可以被操纵，使其偏离使用crm1介导的核输出途径，而是通过大多数细胞mrna使用的NXF1途径输出。然而，我们发现通过这两种途径输出的RNA分子不能有效地共包装，这表明输出途径影响这些RNA的亚细胞定位。我们目前在这个项目中的工作重点是使用高速、高分辨率显微镜检测HIV-1 RNA通过核孔复合体的输出动态。我们正在研究通过CRM1或NXF1途径的输出动力学，并探索不同的输出途径是否使用不同的核孔复合物。我们也在研究HIV-1用来调节哪些rna和多少rna被包装的机制。此外，我们正在使用RNA结合蛋白来重定向HIV-1 RNA包装特异性，我们正在使用超分辨率显微镜来研究病毒颗粒中的RNA结构。这些研究将使我们了解几个对艾滋病毒复制至关重要的问题，这些问题可用于制定阻止艾滋病毒传播的新策略。【对应2011年10月HIV耐药项目实地考察报告中的胡项目2】

Full-length HIV-1 RNA needs to be exported from the nucleus to carry out its functions, including serving as a template for Gag/Gag-Pol translation and as a genome in the newly assembled virion. To study HIV-1 RNA packaging, we have developed a novel assay to directly visualize viral RNA in the particles at single-RNA-molecule sensitivity. This assay reveals that most HIV-1 particles contain viral RNA. Although it is known that retroviral RNAs packaged into particles are dimeric, standard biochemical assays cannot determine the number of RNA molecules in one particle; our results provide evidence to support the long-standing assumption that two RNA molecules (one dimer) are packaged into a particle. To better understand the mechanisms of RNA packaging, we have performed genetic, biochemical, and imaging analyses to show that HIV-1 RNA uses base-pairing of the DIS sequences to select its copackaged RNA partner, and this process occurs in the cytoplasm of the producer cell prior to RNA packaging into particles. We and others have observed that HIV-1 RNA can be manipulated to deviate from using the CRM1-mediated nuclear export pathway and, instead, be exported via the NXF1 pathway, which is used by most cellular mRNAs. However, we found that RNA molecules exported through these two pathways do not copackage efficiently, indicating that the export pathway affects subcellular localization of these RNAs. Our current efforts in this project are focused on examining the dynamics of HIV-1 RNA export using high-speed, high-resolution microscopy to detect export of a single HIV-1 RNA through the nuclear pore complex. We are investigating the kinetics of export via the CRM1 or NXF1 pathways and exploring whether different export pathways use different nuclear pore complexes. We are also investigating the mechanisms that HIV-1 uses to regulate which and how many RNAs are packaged. Additionally, we are using an RNA-binding protein to redirect HIV-1 RNA-packaging specificity, and we are using super-resolution microscopy to study the RNA structure in viral particles. These studies will allow us to understand several questions that are fundamentally important to HIV replication, which can be used to generate new strategies to block the spread of HIV. [Corresponds to Hu Project 2 in the October 2011 site visit report of the HIV Drug Resistance Program]