Schaecher Scott R, Mackenzie Jason M, Pekosz Andrew
Department of Molecular Microbiology, Washington University School of Medicine, Campus Box 8230, 660 S. Euclid Ave., St. Louis, MO 63110-1093, USA.
J Virol. 2007 Jan;81(2):718-31. doi: 10.1128/JVI.01691-06. Epub 2006 Nov 1.
Coronavirus replication is facilitated by a number of highly conserved viral proteins. The viruses also encode accessory genes, which are virus group specific and believed to play roles in virus replication and pathogenesis in vivo. Of the eight putative accessory proteins encoded by the severe acute respiratory distress syndrome associated coronavirus (SARS-CoV), only two-open reading frame 3a (ORF3a) and ORF7a-have been identified in virus-infected cells to date. The ORF7b protein is a putative viral accessory protein encoded on subgenomic (sg) RNA 7. The ORF7b initiation codon overlaps the ORF7a stop codon in a -1 shifted ORF. We demonstrate that the ORF7b protein is expressed in virus-infected cell lysates and from a cDNA encoding the gene 7 coding region, indicating that the sgRNA7 is bicistronic. The translation of ORF7b appears to be mediated by ribosome leaky scanning, and the protein has biochemical properties consistent with that of an integral membrane protein. ORF7b localizes to the Golgi compartment and is incorporated into SARS-CoV particles. We therefore conclude that the ORF7b protein is not only an accessory protein but a structural component of the SARS-CoV virion.
多种高度保守的病毒蛋白促进冠状病毒的复制。这些病毒还编码辅助基因，这些基因具有病毒组特异性，并且被认为在病毒复制和体内发病机制中发挥作用。在严重急性呼吸综合征相关冠状病毒（SARS-CoV）编码的八种假定辅助蛋白中，迄今为止，仅在病毒感染的细胞中鉴定出两种——开放阅读框3a（ORF3a）和ORF7a。ORF7b蛋白是一种假定的病毒辅助蛋白，由亚基因组（sg）RNA 7编码。ORF7b起始密码子在一个-1移码的ORF中与ORF7a终止密码子重叠。我们证明ORF7b蛋白在病毒感染的细胞裂解物中表达，并且从编码基因7编码区的cDNA中表达，这表明sgRNA7是双顺反子的。ORF7b的翻译似乎由核糖体渗漏扫描介导，并且该蛋白具有与整合膜蛋白一致的生化特性。ORF7b定位于高尔基体区室，并被整合到SARS-CoV颗粒中。因此，我们得出结论，ORF7b蛋白不仅是一种辅助蛋白，而且是SARS-CoV病毒粒子的结构成分。
