The function of Nup358 in nuclear protein import

核胞质转运通过核孔复合物（NPCs）发生，这是一种嵌入内外核膜之间的大结构。核孔蛋白（NPC的组成部分）不对称地定位于NPC的核侧或细胞质侧，被认为是运输复合物的初始或终端结合位点。然而，细胞质核孔蛋白Nup214和Nup358最近被证明对于标准进口货物进入细胞核的运输是必不可少的。与标准货物的这些发现相反，我们发现两种蛋白质，其核输入在nup358缺陷细胞中严重受损。人类免疫缺陷病毒的Rev蛋白和细胞蛋白TERT（端粒酶逆转录酶）在对照细胞中都是细胞核，但在Nup358浓度降低的细胞中主要局限于细胞质。因此，我们开始从Wiemann博士（DKFZ, Heidelberg）获得的大量开放阅读框中分析nup358缺失对蛋白质的影响。我们的初步结果表明，大约5-10%的核蛋白需要Nup358才能有效地导入核。我们的目标是：a)鉴定更多的nup358依赖蛋白。b)表征候选蛋白的核输入途径，并分析nup358依赖性输入的潜在分子机制。c)分析Nup214依赖性蛋白的潜在进口。

Nucleocytoplasmic transport occurs through nuclear pore complexes (NPCs), large structures that are embedded between the inner and outer nuclear membrane. Nucleoporins (the components of the NPC) that localize asymmetrically to either the nuclear or the cytoplasmic side of the NPC have been suggested to function as initial or terminal binding sites for transport complexes. The cytoplasmic nucleoporins Nup214 and Nup358, however, were recently shown to be dispensable for transport of standard import cargoes into the nucleus. In contrast to these findings on standard cargoes, we found two proteins, whose nuclear import is strongly impaired in Nup358-deficient cells. The Rev protein of the human immunodeficiency virus and the cellular protein TERT (telomerase reverse transcriptase) are both nuclear in control cells but largely restricted to the cytoplasm in cells with reduced concentrations of Nup358. We therefore set out to analyze the effect of Nup358-depletion on proteins from a large collection of open reading frames obtained from Dr. Wiemann (DKFZ, Heidelberg). Our preliminary results suggest that about 5-10% of nuclear proteins require Nup358 for efficient nuclear import. Our goals are: a) to identify more Nup358-dependent proteins. b) to characterize the nuclear import pathways of our candidate proteins and to analyze the underlying molecular mechanisms of Nup358-dependent import. c) to analyze potential Nup214- dependent import of proteins.