Wang H W, Chen P J, Lee C Z, Wu H L, Chen D S
Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei.
J Virol. 1994 Oct;68(10):6363-71. doi: 10.1128/JVI.68.10.6363-6371.1994.
Hepatitis delta virus (HDV) is composed of four specific components. The first component is envelope protein which contains hepatitis B surface antigens. The second and third components are nucleocapsid proteins, referred to as small and large hepatitis delta antigens (HDAgs). The final component is a single-stranded circular RNA molecule known as the viral genome. In order to study the mechanism of HDV RNA packaging, a four-plasmid cotransfection system in which each viral component was provided by a separate plasmid was employed. Virus-like particles released from Huh-7 cells receiving such a cotransfection were found to contain HDV RNA along with three proteins. Therefore, the four-plasmid cotransfection system could lead to successful HDV RNA packaging in vitro. The system was then used to show that the large HDAg alone was able to achieve a low level of HDV RNA packaging. Analysis of a variety of large HDAg mutants revealed that the RNA-binding domain was essential for viral RNA packaging. By increasing the incorporation of small HDAg into virus-like particles, we found a three- to fourfold enhancement of HDV RNA packaging. This effect was probably through a direct binding of HDV RNA, independent from that of large HDAg, with the small HDAg. The subsequent RNA-protein complex was packaged into particles. The results provided insight into the roles and functional domains of small and large HDAgs in HDV RNA packaging.
丁型肝炎病毒（HDV）由四个特定成分组成。第一个成分是包膜蛋白，其含有乙型肝炎表面抗原。第二和第三个成分是核衣壳蛋白，分别称为小和大丁型肝炎抗原（HDAg）。最后一个成分是单链环状RNA分子，即病毒基因组。为了研究HDV RNA包装机制，采用了一种四质粒共转染系统，其中每个病毒成分由一个单独的质粒提供。从接受这种共转染的Huh-7细胞释放的病毒样颗粒被发现含有HDV RNA以及三种蛋白质。因此，四质粒共转染系统能够在体外成功实现HDV RNA包装。然后利用该系统表明，单独的大HDAg能够实现低水平的HDV RNA包装。对多种大HDAg突变体的分析表明，RNA结合结构域对于病毒RNA包装至关重要。通过增加小HDAg掺入病毒样颗粒，我们发现HDV RNA包装增强了三到四倍。这种效应可能是通过HDV RNA与小HDAg的直接结合，独立于大HDAg与小HDAg的结合。随后的RNA-蛋白质复合物被包装到颗粒中。这些结果为小和大HDAg在HDV RNA包装中的作用和功能结构域提供了见解。
