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Function and molecular properties of nuclear pore-targeting complex

核孔靶向复合物的功能和分子特性

基本信息

批准号：
09680692
负责人：
IMAMOTO Naoko
金额：
$ 2.11万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09680692/
关键词：
nuclear protein transport Importin α Importin β nuclear pore-targeting complex nuclear localization signal Ran β-catenin 核タンパク質輸送

项目摘要

Nuclear import of proteins arc initiated by nuclear localization signal (NLS)-dependent complex formation, termed the nuclear pore-targeting complex (PTAC), in the cytoplasm. PTAC is a stable protein complex composed of a karyophilic protein and two cytosolic components termed PTAC58/importin α and PTAC97/importin β. Importin α directly binds to NLS of karyophile and importin β provides nuclear pore complex (NPC) binding site for PTAC. We analyzed the properties of importin α and importin β, and obtained the following results : 1. We have identified three additional mouse genes homologous to the known importin α, and showed that the mouse importin α can be classified into three subfamilies (Rch1, NPI1, and Qip1), showing approximately 50% amino acid identity to one another. 2. We showed that importin α family proteins show some specificities in the recognition of substrates. For example, Qip1 recognizes a very restricted NLS, requiring both the upstream sequence and basic core sequence … More of Q1 ATPase for its substrate recognition. The other evidence is that tyrosine phosphorylated Stat his recognized by NPI1, but not Rch1. Stat 1 apparently does not possess typical basic-type NLS, and it binds to different portion of NPI1 from those of SV40 T-antigen basic NLS binding site. 3. We examined the behavior and functional domain of importin β Importin β rapidly shuttles between the cytoplasm and the nucleus through NPCs. The use of deletion mutants reveals that NPC-translocation of importin β requires neither Ran- nor importin α-binding but only the NPC-binding domain of this molecule. NPC translocation of importin β was found to require neither Ran nor its GTP hydrolysis. Furthermore, importin β possesses ability to translocate NPC on its own. This could be a common feature of transport factors that carries certain cargos through NPCs into and out of the nucleus. 4. We examined the nuclear import of β-catenin and found that b-catenin can translocate NPCs on it own without requiring soluble factors including Ran. Β-catenin is likely to share the same property with importin β for NPC translocation. Less

蛋白质的核输入是由细胞质中依赖于核定位信号(NLS)的复合体(称为核孔靶向复合体(PTAC))启动的。PTAC是一种稳定的蛋白质复合体，由一个亲核蛋白和两个胞浆组分组成，分别称为PTAC58/Importinα和PTAC97/Importinβ。Importinα直接与亲核细胞的NLS结合，Importinβ为PTAC提供核孔复合体结合部位。我们对Importinα和Importinβ的性质进行了分析，得到了以下结果：1.我们另外鉴定了三个与已知的Importinα同源的小鼠基因，发现小鼠Importinα可以分为三个亚家族(Rch1、NpI1和Qip1)，它们之间的氨基酸同源性约为50%。2.我们发现Importinα家族蛋白在识别底物方面表现出一定的特异性。例如，Qip1识别非常受限的NLS，需要上游序列和基本核心序列…更多的是Q1 ATPase对其底物的识别。另一个证据是，酪氨酸使STAT被NPI1识别，但不能被Rch1识别。STAT-1显然不具有典型的基本型NLS，它与NPI1的结合部位与SV40T抗原碱性NLS结合部位不同。3.研究了ImportinβImportinβ通过核祖细胞快速穿梭于胞浆和胞核之间的行为和功能结构域。缺失突变体的使用表明，Importinβ的NPC易位既不需要Ran-也不需要导入α结合区域，而只需要该分子的NPC结合区域。进口蛋白β的鼻咽癌易位既不需要RAN，也不需要它的GTP水解酶。此外，Importinβ还具有自行移位鼻咽癌的能力。这可能是运输因素的一个共同特征，它将某些货物通过NPC运进和运出原子核。4.我们对β-连环蛋白的核进口进行了检测，发现b-连环蛋白可以在不需要包括RAN在内的可溶性因子的情况下，自行转位NPC。对于鼻咽癌易位，Β-连环蛋白可能与进口蛋白β具有相同的性质。较少