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细节知之甚少。该过程的一部分受异质核核糖核蛋白A2 (hnRNP A2) 的活性控制。本研究研究了hnRNP A2在HeLa细胞中真正的前病毒表达中的作用。使用免疫荧光和荧光原位杂交技术,我们显示了HIV-1-expressing细胞中hnRNP A2表达的敲低导致HIV-1基因组RNA在与微管组织中心 (MTOC) 相对应的独特细胞质空间中快速积累。即使在hnRNP A2-response元件 (A2RE) 中携带突变的前病毒的表达过程中,由于hnRNP A2敲除,RNA也会在细胞核中离开并在MTOC区域积累,其表达导致基因组RNA的核保留。我们还证明hnRNP A2表达是细胞质中来自MTOC的基因组RNA下游运输所必需的。hnRNP A2敲低的结果和Rab7-interacting溶酶体蛋白的过表达在MTOC上的基因组RNA定位对pr55Gag的合成几乎没有影响,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定位调节病毒组装,并且MTOC充当HIV-1基因组RNA从细胞核退出后会聚的中心位点,宿主蛋白hnrnpa2在将其带到和从细胞中的该位点中起着核心作用。

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