Department of Medicine, Division of Infectious Diseases and Epidemiology, Penn State College of Medicine, Hershey, PA 17033, USA.
Department of Microbiology & Immunology, Penn State College of Medicine, Hershey, PA 17033, USA.
Viruses. 2021 May 13;13(5):903. doi: 10.3390/v13050903.
Retroviruses are unique in that they package their RNA genomes as non-covalently linked dimers. Failure to dimerize their genomes results in decreased infectivity and reduced packaging of genomic RNA into virus particles. Two models of retrovirus genome dimerization have been characterized: in murine leukemia virus (MLV), genomic RNA dimerization occurs co-transcriptionally in the nucleus, resulting in the preferential formation of genome homodimers; whereas in human immunodeficiency virus (HIV-1), genomic RNA dimerization occurs in the cytoplasm and at the plasma membrane, with a random distribution of heterodimers and homodimers. Although in vitro studies have identified the genomic RNA sequences that facilitate dimerization in Rous sarcoma virus (RSV), in vivo characterization of the location and preferences of genome dimerization has not been performed. In this study, we utilized three single molecule RNA imaging approaches to visualize genome dimers of RSV in cultured quail fibroblasts. The formation of genomic RNA heterodimers within cells was dependent on the presence of the dimerization initiation site (DIS) sequence in the L3 stem. Subcellular localization analysis revealed that heterodimers were present the nucleus, cytoplasm, and at the plasma membrane, indicating that genome dimers can form in the nucleus. Furthermore, single virion analysis revealed that RSV preferentially packages genome homodimers into virus particles. Therefore, the mechanism of RSV genomic RNA dimer formation appears more similar to MLV than HIV-1.
逆转录病毒的独特之处在于它们将 RNA 基因组包装成非共价连接的二聚体。如果不能使基因组二聚化，就会导致感染性降低，基因组 RNA 包装到病毒颗粒中的比例降低。已经描述了两种逆转录病毒基因组二聚化模型：在鼠白血病病毒（MLV）中，基因组 RNA 在核内转录过程中发生二聚化，导致基因组同源二聚体的优先形成；而在人类免疫缺陷病毒（HIV-1）中，基因组 RNA 二聚化发生在细胞质和质膜中，异源二聚体和同源二聚体随机分布。尽管体外研究已经鉴定了促进劳斯肉瘤病毒（RSV）二聚化的基因组 RNA 序列，但尚未对体内基因组二聚化的位置和偏好性进行表征。在这项研究中，我们利用三种单分子 RNA 成像方法来可视化培养的鹌鹑成纤维细胞中 RSV 的基因组二聚体。细胞内基因组 RNA 异源二聚体的形成依赖于 L3 茎中的二聚化起始位点（DIS）序列的存在。亚细胞定位分析表明异源二聚体存在于细胞核、细胞质和质膜中，表明基因组二聚体可以在核内形成。此外，单个病毒粒子分析表明 RSV 优先将基因组同源二聚体包装到病毒粒子中。因此，RSV 基因组 RNA 二聚体形成的机制似乎更类似于 MLV 而不是 HIV-1。
