Chao M, Hsieh S Y, Taylor J
Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111.
J Virol. 1991 Aug;65(8):4057-62. doi: 10.1128/JVI.65.8.4057-4062.1991.
The only known protein of hepatitis delta virus (HDV), the delta antigen, is found both within virus particles and within the nucleus of the infected cell, where it has one or more roles essential for RNA genome replication. Others have demonstrated that the antigen has the ability, in vitro, to specifically bind HDV RNA species. We report a further examination of this phenomenon, using partially purified recombinant protein, expressed as a fusion with the staphylococcal protein A. From Northwestern (RNA-immunoblot) analyses with both complete and various subdomains of HDV genomic and antigenomic RNAs, we found that a necessary feature for specific binding was that the RNA be able to fold to some extent into the so-called rodlike structure; this structure is a predicted intramolecular partial base-pairing of the circular RNA, with about 70% of all bases involved, so as to produce an unbranched rodlike structure. Six different subregions of the HDV rodlike structure, three on the genomic RNA and three on its complement, the antigenomic RNA, were tested and found to be sufficient for antigen binding. However, features in addition to the rodlike structure may also be necessary for specific binding, because we found that a similar structure present in the RNA of the potato spindle tuber viroid did not allow binding.
丁型肝炎病毒（HDV）唯一已知的蛋白质——丁型抗原，存在于病毒颗粒内部以及受感染细胞的细胞核中，在那里它对RNA基因组复制起着一个或多个至关重要的作用。其他人已经证明，该抗原在体外具有特异性结合HDV RNA种类的能力。我们报告了对这一现象的进一步研究，使用部分纯化的重组蛋白，该重组蛋白作为与葡萄球菌蛋白A的融合蛋白表达。通过对HDV基因组和反基因组RNA的完整片段以及各种亚结构域进行蛋白质印迹（RNA免疫印迹）分析，我们发现特异性结合的一个必要特征是RNA能够在一定程度上折叠成所谓的杆状结构；这种结构是环状RNA预测的分子内部分碱基配对，约70%的碱基参与其中，从而产生无分支的杆状结构。对HDV杆状结构的六个不同亚区域进行了测试，其中三个位于基因组RNA上，三个位于其互补链反基因组RNA上，结果发现这些亚区域足以与抗原结合。然而，除了杆状结构外的其他特征可能对于特异性结合也是必要的，因为我们发现马铃薯纺锤块茎类病毒RNA中存在的类似结构并不允许结合。
