Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, 200241, PR China.
Virol J. 2011 Mar 31;8:147. doi: 10.1186/1743-422X-8-147.
Duck hepatitis virus (DHV-1) is a worldwide distributed picornavirus that causes acute and fatal disease in young ducklings. Recently, the complete genome of DHV-1 has been determined and comparative sequence analysis has shown that possesses the typical picornavirus organization but exhibits several unique features. For the first time, we provide evidence that the 626-nucleotide-long 5'-UTR of the DHV-1 genome contains an internal ribosome entry site (IRES) element that functions efficiently both in vitro and in mammalian cells. The prediction of the secondary structure of the DHV-1 IRES shows significant similarity to the hepatitis C virus (HCV) IRES. Moreover, similarly to HCV IRES, DHV-1 IRES can direct translation initiation in the absence of a functional eIF4F complex. We also demonstrate that the activity of the DHV-1 IRES is modulated by a viral coding sequence located downstream of the DHV-1 5'-UTR, which enhances DHV-1 IRES activity both in vitro and in vivo. Furthermore, mutational analysis of the predicted pseudo-knot structures at the 3'-end of the putative DHV-1 IRES supported the presence of conserved domains II and III and, as it has been previously described for other picornaviruses, these structures are essential for keeping the normal internal initiation of translation of DHV-1.
鸭肝炎病毒（DHV-1）是一种分布广泛的小核糖核酸病毒，可导致雏鸭急性和致命疾病。最近，已确定 DHV-1 的完整基因组，比较序列分析表明其具有典型的小核糖核酸病毒结构，但表现出几个独特的特征。我们首次提供证据表明，DHV-1 基因组 626 个核苷酸长的 5'UTR 包含一个内部核糖体进入位点（IRES）元件，该元件在体外和哺乳动物细胞中均能有效发挥作用。DHV-1 IRES 的二级结构预测显示与丙型肝炎病毒（HCV）IRES 具有显著相似性。此外，与 HCV IRES 类似，DHV-1 IRES 可在缺乏功能性 eIF4F 复合物的情况下指导翻译起始。我们还证明，位于 DHV-1 5'UTR 下游的病毒编码序列可调节 DHV-1 IRES 的活性，从而在体外和体内均增强 DHV-1 IRES 的活性。此外，对推定的 DHV-1 IRES 3'末端预测假结结构的突变分析支持保守结构域 II 和 III 的存在，并且与其他小核糖核酸病毒先前描述的情况一样，这些结构对于保持 DHV-1 的正常内部翻译起始是必不可少的。
