Yamshchikov V F, Compans R W
Department of Microbiology, University of Alabama, Birmingham 35294.
Virology. 1993 Jan;192(1):38-51. doi: 10.1006/viro.1993.1006.
In order to determine the requirements for secretion of flavivirus structural proteins, we analyzed the expression of several West Nile flavivirus gene cassettes of different lengths in vaccinia virus expression systems. Expression of the longest cassette coding for the 5'-nontranslated region, proteins C through NS2B, and the protease domain of NS3, resulted in secretion of prM-E complexes and cleavage of prM. The presence and proper processing of the NS2A-NS2B-NS3 region appeared to be necessary for prM-E secretion. These proteins were released from cells mostly as membranous complexes which may represent empty viral envelopes. Cleavage of the membrane-associated intracellular form of protein C (C(i)) to produce the virion form (Ce) appeared to be critical for release of viral proteins. The presence and proper cleavage of the NS2A-NS2B-NS3 region were also found to be necessary for efficient C-prM cleavage by signalases. The NS2B-NS3 complex was implicated in cleavage of the intracellular form of protein C. Formation of a low level of virus-like particles was detected by electron microscopy. A model for virion formation, suggesting a critical role of the NS2B and NS3 proteins, is discussed.
为了确定黄病毒结构蛋白分泌的要求，我们分析了痘苗病毒表达系统中几种不同长度的西尼罗河黄病毒基因盒的表达情况。编码5'-非翻译区、C至NS2B蛋白以及NS3蛋白酶结构域的最长基因盒的表达，导致了prM-E复合物的分泌和prM的切割。NS2A-NS2B-NS3区域的存在和正确加工似乎是prM-E分泌所必需的。这些蛋白大多以膜复合物的形式从细胞中释放出来，这些复合物可能代表空的病毒包膜。将与膜相关的细胞内形式的蛋白C（C(i)）切割产生病毒体形式（Ce）似乎对病毒蛋白的释放至关重要。还发现NS2A-NS2B-NS3区域的存在和正确切割对于信号肽酶有效切割C-prM是必需的。NS2B-NS3复合物与细胞内形式的蛋白C的切割有关。通过电子显微镜检测到形成了低水平的病毒样颗粒。讨论了一个病毒体形成模型，该模型表明NS2B和NS3蛋白起着关键作用。
