Zhao H, Ekström M, Garoff H
Karolinska Institute, Department of Biosciences at Novum, Huddinge, Sweden.
J Gen Virol. 1998 Oct;79 ( Pt 10):2435-46. doi: 10.1099/0022-1317-79-10-2435.
The nucleoprotein (NP) and matrix protein (M1) are the most abundant structural proteins of influenza A virus. M1 forms a protein layer beneath the viral envelope and NP constitutes the protein backbone of the ribonucleoproteins (RNPs). In order to elucidate the functions of these proteins in virus assembly we have expressed NP and M1 in BHK-21 cells using Semliki Forest virus replicons and analysed their molecular interactions. We found that both M1 and NP engaged in extensive homooligomerization reactions soon after synthesis. However, there was no detectable heterooligomerization taking place between the two viral proteins, nor between these and host proteins. One interpretation of these results is that homooligomers, and not monomers, of NP and M1 are used as building blocks during RNP assembly and formation of the submembranous M1 layer, respectively. The complete absence of M1-NP heterooligomers suggests, on the other hand, that these two major viral proteins do not interact directly with each other during virus assembly. We also found that a fraction of M1 associated with cellular membranes. This did not, however, result in membrane budding or vesicularization as was the case with the matrix protein of vesicular stomatitis virus when expressed separately (P. A. Justice and others, Journal of Virology 69, 3156-3160, 1995).
核蛋白（NP）和基质蛋白（M1）是甲型流感病毒中含量最为丰富的结构蛋白。M1在病毒包膜下方形成一层蛋白质层，而NP构成核糖核蛋白（RNP）的蛋白质骨架。为了阐明这些蛋白在病毒组装中的功能，我们利用辛德毕斯病毒复制子在BHK - 21细胞中表达了NP和M1，并分析了它们之间的分子相互作用。我们发现，M1和NP在合成后不久就参与了广泛的同型寡聚化反应。然而，在这两种病毒蛋白之间，以及它们与宿主蛋白之间均未检测到异型寡聚化的发生。这些结果的一种解释是，NP和M1的同型寡聚体，而非单体，分别在RNP组装和膜下M1层形成过程中用作构建模块。另一方面，M1 - NP异型寡聚体的完全缺失表明，这两种主要的病毒蛋白在病毒组装过程中并不直接相互作用。我们还发现，一部分M1与细胞膜相关联。然而，这并未导致膜出芽或形成囊泡，单独表达时水疱性口炎病毒的基质蛋白则会出现这种情况（P. A. 贾斯蒂斯等人，《病毒学杂志》69，3156 - 3160，1995）。
