Brown C M, Dinesh-Kumar S P, Miller W A
Department of Plant Pathology, Iowa State University, Ames 50011, USA.
J Virol. 1996 Sep;70(9):5884-92. doi: 10.1128/JVI.70.9.5884-5892.1996.
Many viruses use stop codon readthrough as a strategy to produce extended coat or replicase proteins. The stop codon of the barley yellow dwarf virus (PAV serotype) coat protein gene is read through at a low rate. This produces an extended polypeptide which becomes part of the virion. We have analyzed the cis-acting sequences in the barley yellow dwarf virus PAV genome required for this programmed readthrough in vitro in wheat germ extracts and reticulocyte lysates and in vivo in oat protoplasts. Two regions 3' to the stop codon were required. Deletion of sections containing the first 5 of the 16 CCN NNN repeats located 3' of the stop codon greatly reduced readthrough in vitro and in vivo. Surprisingly, readthrough also required a second, more distal element that is located 697 to 758 bases 3' of the stop codon within the readthrough open reading frame. This element also functioned in vivo in oat protoplasts when placed more than 2 kb from the coat protein gene stop in the untranslated region following a GUS reporter gene. This is the first report of a long-range readthrough signal in viruses.
许多病毒利用终止密码子通读作为产生延长的外壳蛋白或复制酶蛋白的一种策略。大麦黄矮病毒（PAV血清型）外壳蛋白基因的终止密码子以低频率发生通读。这产生了一种延长的多肽，它成为病毒粒子的一部分。我们已经分析了大麦黄矮病毒PAV基因组中在体外小麦胚提取物和网织红细胞裂解物以及体内燕麦原生质体中进行这种程序性通读所需的顺式作用序列。终止密码子下游需要两个区域。缺失包含位于终止密码子下游16个CCN NNN重复序列中前5个的片段，在体外和体内都大大降低了通读率。令人惊讶的是，通读还需要第二个更远端的元件，它位于通读开放阅读框内终止密码子下游697至758个碱基处。当该元件在GUS报告基因之后的非翻译区中距离外壳蛋白基因终止子超过2 kb时，它在燕麦原生质体中也能在体内发挥作用。这是关于病毒中远距离通读信号的首次报道。
