Article
- The EMBO Journal (2004) 23, 1526 - 1535
- doi:10.1038/sj.emboj.7600154
Published online: 11 March 2004
Subject Categories:
Importin 
associates with membranes and participates in nuclear envelope assembly in vitro
Virginie Hachet, Thomas Köcher, Matthias Wilm and Iain W Mattaj
- European Molecular Biology Laboratory, Meyerhofstrasse, Heidelberg, Germany
Correspondence to:
Iain W Mattaj, Gene Expression Programme, European Molecular Biology Laboratory, Meyerhofstrasse 1, D-69117 Heidelberg, Germany. Tel.: +49 6221 387 393; Fax: +49 6221 387 518; E-mail: mattaj@embl-heidelberg.de
Received 22 December 2003; Accepted 11 February 2004
Abstract
Importin 
is well known as an adaptor that functions with Importin 
in the nuclear import of proteins containing specific nuclear localization signals (NLSs). We show here that either an excess or a lack of Importin blocks nuclear envelope (NE) assembly in vitro, and our data suggest that soluble Importin functions in NE assembly in conjunction with NLS-containing partner proteins. Surprisingly, a significant proportion of Importin is found to fractionate with Xenopus egg membranes. We demonstrate that membrane association of Importin is regulated by phosphorylation. Using mutant forms of Importin that either do not bind membranes or are not released from them by phosphorylation, we provide evidence that membrane-associated Importin is required for NE formation. Unlike other functions of Importin , this membrane-associated activity does not require interaction with NLS proteins.
Keywords:
- Importin ,
- nuclear assembly,
- nuclear envelope,
- protein phosphorylation
- Importin
