Chromatin-bound NLS proteins recruit membrane vesicles and nucleoporins for nuclear envelope assembly via importin-α/β

• Published in: Cell research Vol. 22; no. 11; pp. 1562 - 1575
• Main Authors: Lu, Quanlong, Lu, Zhigang, Liu, Qinying, Guo, Li, Ren, He, Fu, Jingyan, Jiang, Qing, Clarke, Paul R, Zhang, Chuanmao
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.11.2012; Nature Publishing Group
• Subjects: 631/136/334/1874/761; 631/337; 631/80/389/2029; alpha Karyopherins - metabolism; Animals; beta Karyopherins - metabolism; Biomedical and Life Sciences; Cell Biology; Cell Cycle Proteins - metabolism; Chromatin - metabolism; Guanine Nucleotide Exchange Factors - metabolism; HeLa Cells; Humans; Life Sciences; Nuclear Envelope - metabolism; Nuclear Localization Signals - metabolism; Nuclear Pore Complex Proteins - metabolism; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Original; original-article; ran GTP-Binding Protein - metabolism; Xenopus - genetics; Xenopus - metabolism; Xenopus Proteins - metabolism; 囊泡; 审查; 染色质; 核膜; 蛋白质; 装配过程; 贷款; 非洲爪蟾卵提取物; nuclear pore complex; importin; Ran GTPase; nucleoplasmin; nuclear assembly
• ISSN: 1001-0602; 1748-7838
• DOI: 10.1038/cr.2012.113

The mechanism for nuclear envelope （NE） assembly is not fully understood. Importin-β and the small GTPase Ran have been implicated in the spatial regulation of NE assembly process. Here we report that chromatin-bound NLS （nuclear localization sequence） proteins provide docking sites for the NE precursor membrane vesicles and nucleo- porins via importin-a and -β during NE assembly in Xenopus egg extracts. We show that along with the fast recruit- ment of the abundant NLS proteins such as nucleoplasmin and histones to the demembranated sperm chromatin in the extracts, importin-α binds the chromatin NLS proteins rapidly. Meanwhile, importin-β binds cytoplasmic NE precursor membrane vesicles and nucleoporins. Through interacting with importin-α on the chromatin NLS pro- teins, importin-β targets the membrane vesicles and nucleoporins to the chromatin surface. Once encountering Ran- GTP on the chromatin generated by RCC1, importin-β preferentially binds Ran-GTP and releases the membrane vesicles and nucleoporins for NE assembly. NE assembly is disrupted by blocking the interaction between importin-α and NLS proteins with excess soluble NLS proteins or by depletion of importin-β from the extract. Our findings reveal a novel molecular mechanism for NE assembly in Xenopus egg extracts.