Wu T T, Bichko V V, Ryu W S, Lemon S M, Taylor J M
Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111-2497, USA.
J Virol. 1995 Nov;69(11):7226-31. doi: 10.1128/JVI.69.11.7226-7231.1995.
During the replication cycle of hepatitis delta virus (HDV), RNA editing occurs at position 1012 on the 1679-nucleotide RNA genome. This changes an A to G in the amber termination codon, UAG, of the small form of the delta antigen (delta Ag). The resultant UGG codon, tryptophan, allows the translation of a larger form of the delta Ag with a 19-amino-acid C-terminal extension. Using HDV cDNA-transfected cells, we examined the editing potential of HDV RNA mutated from G to A at 1011 on the antigenome, adjacent to normal editing site at 1012. Four procedures were used to study not only the editing of the A at 1012, but also that of the new A at 1011: (i) nucleotide sequencing, (ii) a PCR-based RNA-editing assay, (iii) immunoblot assays, and (iv) immunofluorescence. Five findings are reported. (i) Even after the mutation at 1011, editing still occurred at 1012. (ii) Site 1011 itself now acted as a novel RNA-editing site. (iii) Sites 1011 and 1012 were edited independently. (iv) At later times, both sites became edited, thereby allowing the synthesis of the large form of the delta Ag (delta Ag-L). (v) Via immunofluorescence, such double editing became apparent as a stochastic event, in that groups of cells arose in which the changes had taken place. Evaluation of these findings and of those from previous studies of the stability of the HDV genomic sequence (H.J. Netter et al., J. Virol. 69:1687-1692, 1995) supports both the recent reevaluation of HDV RNA editing as occurring on antigenomic RNA (Casey and Gerin, personal communication) and the interpretation that editing occurs via the RNA-modifying enzyme known as DRADA.
在丁型肝炎病毒（HDV）的复制周期中，RNA编辑发生在1679个核苷酸的RNA基因组的1012位。这使得丁型抗原（δAg）小形式的琥珀色终止密码子UAG中的A变为G。产生的UGG密码子（色氨酸）使得能够翻译出具有19个氨基酸C末端延伸的更大形式的δAg。我们使用HDV cDNA转染的细胞，研究了抗原组上1011位从G突变为A的HDV RNA的编辑潜力，该位置与正常编辑位点1012相邻。我们采用了四种方法来研究1012位A的编辑情况，以及新出现的1011位A的编辑情况：（i）核苷酸测序，（ii）基于PCR的RNA编辑检测，（iii）免疫印迹检测，以及（iv）免疫荧光检测。我们报告了五项发现。（i）即使在1011位发生突变后，1012位仍会发生编辑。（ii）1011位自身现在充当了一个新的RNA编辑位点。（iii）1011位和1012位的编辑是独立进行的。（iv）在随后的时间里，两个位点都发生了编辑，从而使得能够合成更大形式的δAg（δAg-L）。（v）通过免疫荧光检测，这种双重编辑表现为一个随机事件，即出现了发生了这些变化的细胞群。对这些发现以及先前关于HDV基因组序列稳定性研究结果（H.J. Netter等人，《病毒学杂志》69:1687 - 1692，1995）的评估，既支持了最近将HDV RNA编辑重新评估为发生在抗原组RNA上的观点（Casey和Gerin，个人交流），也支持了编辑是通过被称为DRADA的RNA修饰酶发生的这一解释。
