Importin provides a link between nuclear protein import and U snRNA export

Item Type:	Article
Title:	Importin provides a link between nuclear protein import and U snRNA export
Creators Name:	Goerlich, D. and Kraft, R. and Kostka, S. and Vogel, F. and Hartmann, E. and Laskey, R.A. and Mattaj, I.W. and Izaurralde, E.
Abstract:	Importin-alpha mediates nuclear protein import by binding nuclear localization signals and importin-beta. We find approximately 30% of SRP1p, the yeast importin-alpha, in a nuclear complex with the Saccharomyces cerevisiae nuclear cap-binding protein complex (CBC). Similarly, a large fraction of Xenopus CBC is associated with importin-alpha in the nucleus. CBC promotes nuclear export of capped U snRNAs and shuttles between nucleus and cytoplasm. The CBC-importin-alpha complex binds specifically to capped RNA, suggesting that CBC might shuttle while bound to importin-alpha. Strikingly, importin-beta binding displaces the RNA from the CBC-importin-alpha complex. Thus, the commitment of CBC for nuclear reentry triggers the release of the export substrate into the cytoplasm. We provide evidence for a mechanism that ensures that importin-mediated RNA release is a specifically cytoplasmic event.
Keywords:	alpha Karyopherins, Amino Acid Sequence, Biological Transport, Cell Nucleus, Cytoplasm, Fungal Genes, Guanosine Triphosphate, Karyopherins, Molecular Sequence Data, Nuclear Proteins, Oocytes, Protein Binding, ran GTP-Binding Protein, RNA Cap-Binding Proteins, RNA Caps, RNA-Binding Proteins, Saccharomyces Cerevisiae, Small Nuclear RNA, Animals, Xenopus
Source:	Cell
ISSN:	0092-8674
Publisher:	Cell Press
Volume:	87
Number:	1
Page Range:	21-32
Date:	4 October 1996
Official Publication:	https://doi.org/10.1016/S0092-8674(00)81319-7
PubMed:	View item in PubMed

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