Few details are known about how the human immunodeficiency virus type 1 (HIV-1) genomic RNA is trafficked in the cytoplasm. Part of this process is controlled by the activity of heterogeneous nuclear ribonucleoprotein A2 (hnRNP A2). The role of hnRNP A2 during the expression of a bona fide provirus in HeLa cells is investigated in this study. Using immunofluorescence and fluorescence in situ hybridization techniques, we show that knockdown of hnRNP A2 expression in HIV-1-expressing cells results in the rapid accumulation of HIV-1 genomic RNA in a distinct, cytoplasmic space that corresponds to the microtubule-organizing center (MTOC). The RNA exits in the nucleus and accumulates at the MTOC region as a result of hnRNP A2 knockdown even during the expression of a provirus harboring mutations in the hnRNP A2-response element (A2RE), the expression of which results in nuclear retention of genomic RNA. We also demonstrate that hnRNP A2 expression is required for downstream trafficking of genomic RNA from the MTOC in the cytoplasm. Genomic RNA localization at the MTOC that was both the result of hnRNP A2 knockdown and the overexpression of Rab7-interacting lysosomal protein had little effect on pr55Gag synthesis but negatively influenced virus production and infectivity. These data indicate that altered HIV-1 genomic RNA localization modulates viral assembly and that the MTOC serves as a central site to which HIV-1 genomic RNA converges following its exit from the nucleus, with the host protein, hnRNP A2, playing a central role in taking it to and from this site in the cell.

译文

关于人类免疫缺陷病毒1型(HIV-1)基因组RNA如何在细胞质中运输的信息鲜为人知。该过程的一部分由异质核糖核蛋白A2(hnRNP A2)的活性控制。这项研究调查了hnRNP A2在HeLa细胞中表达真正的原病毒的过程中的作用。使用免疫荧光和荧光原位杂交技术,我们显示敲低表达HIV-1的细胞中hnRNP A2表达的表达导致HIV-1基因组RNA在与微管组织中心相对应的独特细胞质空间中的快速积累( MTOC)。即使hnRNP A2反应元件(A2RE)中携带有突变的原病毒表达,RNA仍会通过hnRNP A2敲除而留在细胞核中并在MTOC区域积聚,其表达会导致基因组RNA的核保留。我们还证明hnRNP A2表达是从细胞质MTOC下游运输基因组RNA所必需的。基因组RNA在MTOC处的定位既是hnRNP A2敲除的结果,又是与Rab7相互作用的溶酶体蛋白的过表达,对pr55Gag的合成影响很小,但对病毒的产生和感染性产生负面影响。这些数据表明,改变的HIV-1基因组RNA定位可调节病毒装配,MTOC充当HIV-1基因组RNA从细胞核退出后向其汇聚的中心位点,宿主蛋白hnRNP A2发挥着核心作用。将其带入和移出该单元格中的此站点。

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