Department of Biochemistry I, Faculty of Medicine, Georg-August-University of Göttingen, Humboldtallee 23, 37073, Göttingen, Germany.
Traffic. 2012 Feb;13(2):218-33. doi: 10.1111/j.1600-0854.2011.01302.x. Epub 2011 Nov 21.
In vertebrates, the nuclear pore complex (NPC), the gate for transport of macromolecules between the nucleus and the cytoplasm, consists of approximately 30 different nucleoporins (Nups). The Nup and SUMO E3-ligase Nup358/RanBP2 are the major components of the cytoplasmic filaments of the NPC. In this study, we perform a structure-function analysis of Nup358 and describe its role in nuclear import of specific proteins. In a screen for nuclear proteins that accumulate in the cytoplasm upon Nup358 depletion, we identified proteins that were able to interact with Nup358 in a receptor-independent manner. These included the importin α/β-cargo DBC-1 (deleted in breast cancer 1) and DMAP-1 (DNA methyltransferase 1 associated protein 1). Strikingly, a short N-terminal fragment of Nup358 was sufficient to promote import of DBC-1, whereas DMAP-1 required a larger portion of Nup358 for stimulated import. Neither the interaction of RanGAP with Nup358 nor its SUMO-E3 ligase activity was required for nuclear import of all tested cargos. Together, Nup358 functions as a cargo- and receptor-specific assembly platform, increasing the efficiency of nuclear import of proteins through various mechanisms.
在脊椎动物中，核孔复合物（NPC）是核质间大分子运输的门户，由大约 30 种不同的核孔蛋白（Nups）组成。Nup 和 SUMO E3 连接酶 Nup358/RanBP2 是 NPC 细胞质丝的主要成分。在这项研究中，我们对 Nup358 进行了结构-功能分析，并描述了它在特定蛋白质核输入中的作用。在 Nup358 耗尽时，我们进行了一个筛选核蛋白在细胞质中积累的筛选，鉴定出了能够以受体非依赖的方式与 Nup358 相互作用的蛋白质。这些包括 importin α/β-cargo DBC-1（乳腺癌 1 缺失）和 DMAP-1（DNA 甲基转移酶 1 相关蛋白 1）。引人注目的是，Nup358 的短 N 端片段足以促进 DBC-1 的输入，而 DMAP-1 则需要 Nup358 的更大部分才能刺激输入。RanGAP 与 Nup358 的相互作用及其 SUMO-E3 连接酶活性均不是所有测试 cargo 核输入所必需的。总之，Nup358 作为一种货物和受体特异性组装平台，通过多种机制提高了蛋白质的核输入效率。
