Export of importin alpha from the nucleus is mediated by a specific nuclear transport factor
Export of importin alpha from the nucleus is mediated by a specific nuclear transport factor
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DOI：
10.1016/s0092-8674(00)80372-4
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发表时间：
1997-09-19
期刊：
影响因子：
64.5
通讯作者：
Gorlich, D
中科院分区：
文献类型：
--
作者：
Kutay, U;Bischoff, FR;Gorlich, D
NLS 蛋白通过导入 α/β 异二聚体转运到细胞核中。输入蛋白 α 结合 NLS，而输入蛋白 β 介导通过核孔复合体的易位。易位后，RanGTP（其预测浓度在细胞核中较高，在细胞质中较低）结合输入蛋白β并取代输入蛋白α。然后，Importin alpha 必须返回细胞质，留下 NLS 蛋白。在这里，我们报告先前鉴定的 CAS 蛋白介导输入和 α 再输出。仅在 RanGTP 存在的情况下，CAS 才会与 importin α 牢固结合，形成 importin α/CAS/RanGTP 复合物。通过 RanBP1 和 RanGAP1 的联合作用，Importin α 从细胞质中的复合物中释放出来。 CAS 优先与不含 NLS 的输入蛋白 α 结合，这解释了为什么输入底物保留在细胞核中。
NLS proteins are transported into the nucleus by the importin alpha/beta heterodimer. Importin alpha binds the NLS, while importin beta mediates translocation through the nuclear pore complex. After translocation, RanGTP, whose predicted concentration is high in the nucleus and low in the cytoplasm, binds importin beta and displaces importin alpha. Importin alpha must then be returned to the cytoplasm, leaving the NLS protein behind. Here, we report that the previously identified CAS protein mediates importin alpha re-export. CAS binds strongly to importin alpha only in the presence of RanGTP, forming an importin alpha/CAS/RanGTP complex. Importin alpha is released from this complex in the cytoplasm by the combined action of RanBP1 and RanGAP1. CAS binds preferentially to NLS-free importin alpha, explaining why import substrates stay in the nucleus.