Tijms Marieke A, van der Meer Yvonne, Snijder Eric J
Molecular Virology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, LUMC E4-P, PO Box 9600, 2300 RC Leiden, The Netherlands1.
J Gen Virol. 2002 Apr;83(Pt 4):795-800. doi: 10.1099/0022-1317-83-4-795.
RNA synthesis (genome replication and subgenomic mRNA transcription) directed by equine arteritis virus (EAV; family Arteriviridae, order Nidovirales) occurs on modified cytoplasmic membranes to which most viral replicase subunits localize. Remarkably, a fraction of non-structural protein 1 (nsp1), a protein essential for transcription but dispensable for genome replication, is present in the host cell nucleus, in particular during the earlier stages of infection. Expression of GFP-tagged fusion proteins revealed that nsp1 is actively imported into the nucleus. Although the signals responsible for nsp1 transport could not be identified, our studies revealed that another EAV protein with a partially nuclear localization, the nucleocapsid (N) protein, utilizes the CRM1-mediated nuclear export pathway. Inactivation of this pathway with the drug leptomycin B resulted in the unexpected and immediate nuclear retention of all N protein molecules, thus revealing that the protein shuttles between cytoplasm and nucleus before playing its role in cytoplasmic virus assembly.
马动脉炎病毒（EAV；动脉炎病毒科，尼多病毒目）指导的RNA合成（基因组复制和亚基因组mRNA转录）发生在修饰的细胞质膜上，大多数病毒复制酶亚基定位于此。值得注意的是，非结构蛋白1（nsp1）的一部分，一种对转录必不可少但对基因组复制可有可无的蛋白质，存在于宿主细胞核中，尤其是在感染的早期阶段。绿色荧光蛋白标记的融合蛋白的表达表明nsp1被主动转运到细胞核中。尽管无法确定负责nsp1转运的信号，但我们的研究表明，另一种具有部分核定位的EAV蛋白，核衣壳（N）蛋白，利用CRM1介导的核输出途径。用药物雷帕霉素B使该途径失活导致所有N蛋白分子意外且立即被核滞留，从而揭示该蛋白在细胞质中发挥其在病毒组装中的作用之前在细胞质和细胞核之间穿梭。
