Kann M, Sodeik B, Vlachou A, Gerlich W H, Helenius A
Institute of Medical Virology, Justus Liebig University, D-35392 Giessen, Germany.
J Cell Biol. 1999 Apr 5;145(1):45-55. doi: 10.1083/jcb.145.1.45.
Although many viruses replicate in the nucleus, little is known about the processes involved in the nuclear import of viral genomes. We show here that in vitro generated core particles of human hepatitis B virus bind to nuclear pore complexes (NPCs) in digitonin-permeabilized mammalian cells. This only occurred if the cores contained phosphorylated core proteins. Binding was inhibited by wheat germ agglutinin, by antinuclear pore complex antibodies, and by peptides corresponding either to classical nuclear localization signals (NLS) or to COOH-terminal sequences of the core protein. Binding was dependent on the nuclear transport factors importins (karyopherins) alpha and beta. The results suggested that phosphorylation induces exposure of NLS in the COOH-terminal portion of the core protein that allows core binding to the NPCs by the importin- (karyopherin-) mediated pathway. Thus, phosphorylation of the core protein emerged as an important step in the viral replication cycle necessary for transport of the viral genome to the nucleus.
尽管许多病毒在细胞核中复制，但对于病毒基因组核输入所涉及的过程却知之甚少。我们在此表明，体外生成的人乙型肝炎病毒核心颗粒可与洋地黄皂苷通透的哺乳动物细胞中的核孔复合体（NPC）结合。仅当核心颗粒含有磷酸化的核心蛋白时才会发生这种情况。小麦胚凝集素、抗核孔复合体抗体以及对应于经典核定位信号（NLS）或核心蛋白羧基末端序列的肽均可抑制这种结合。这种结合依赖于核转运因子输入蛋白（核转运蛋白）α和β。结果表明，磷酸化诱导核心蛋白羧基末端部分的NLS暴露，从而使核心颗粒通过输入蛋白（核转运蛋白）介导的途径与NPC结合。因此，核心蛋白的磷酸化成为病毒复制周期中病毒基因组转运至细胞核所必需的重要步骤。
