Department of Biochemistry, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan.
Mol Biol Cell. 2010 Jun 1;21(11):1885-96. doi: 10.1091/mbc.e09-12-1041. Epub 2010 Apr 7.
Nup98 is a mobile nucleoporin that forms distinct dots in the nucleus, and, although a role for Nup98 in nuclear transport has been suggested, its precise function remains unclear. Here, we show that Nup98 plays an important role in Crm1-mediated nuclear protein export. Nuclear, but not cytoplasmic, dots of EGFP-tagged Nup98 disappeared rapidly after cell treatment with leptomycin B, a specific inhibitor of the nuclear export receptor, Crm1. Mutational analysis demonstrated that Nup98 physically and functionally interacts with Crm1 in a RanGTP-dependent manner through its N-terminal phenylalanine-glycine (FG) repeat region. Moreover, the activity of the Nup98-Crm1 complex was modulated by RanBP3, a known cofactor for Crm1-mediated nuclear export. Finally, cytoplasmic microinjection of anti-Nup98 inhibited the Crm1-dependent nuclear export of proteins, concomitant with the accumulation of anti-Nup98 in the nucleus. These results clearly demonstrate that Nup98 functions as a novel shuttling cofactor for Crm1-mediated nuclear export in conjunction with RanBP3.
Nup98 是一种可移动的核孔蛋白，在核内形成明显的小点。虽然已经有人提出 Nup98 在核转运中发挥作用，但它的确切功能仍不清楚。在这里，我们表明 Nup98 在 Crm1 介导的核蛋白输出中发挥重要作用。细胞用莱普霉素 B 处理后，核内（而非细胞质内）的 EGFP 标记的 Nup98 点迅速消失，莱普霉素 B 是核输出受体 Crm1 的特异性抑制剂。突变分析表明，Nup98 通过其 N 端苯丙氨酸-甘氨酸（FG）重复区以 RanGTP 依赖性的方式与 Crm1 发生物理和功能相互作用。此外，RanBP3 调节 Nup98-Crm1 复合物的活性，RanBP3 是 Crm1 介导的核输出的已知共因子。最后，细胞质内微注射抗 Nup98 抑制了 Crm1 依赖性的核蛋白输出，同时抗 Nup98 在核内积累。这些结果清楚地表明，Nup98 作为一种新型穿梭共因子，与 RanBP3 一起参与 Crm1 介导的核输出。
