Cse1p Is Required for Export of Srp1p/Importin-α from the Nucleus in Saccharomyces cerevisiae*
- From the Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, and the Dana-Farber Cancer Institute, Boston, Massachusetts 02115
Abstract
In metazoan cells, the CAS protein has been shown to function as a recycling factor for the importin-α subunit of the classical nuclear localization signal receptor, exporting importin-α from the nucleus to allow its participation in multiple rounds of nuclear import. CAS is a member of a family of proteins that bear homology to the larger subunit of the nuclear localization signal receptor, importin-β, and that are found in all eukaryotes from yeast to humans. Sequence similarity identifies the product of theSaccharomyces cerevisiae CSE1 gene as a potential CAS homologue. Here we present evidence that Cse1p is the functional homologue of CAS: Cse1p is required to prevent accumulation of Srp1p/importin-α in the nucleus, it localizes to the nuclear envelope in a pattern typical of nuclear transport receptors, and it associatesin vivo with Srp1p in a nucleotide-specific manner. We show further that mutations in CSE1 and SRP1 have specific effects on their association and on the intracellular localization of Cse1p.
Footnotes
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↵* This work was supported by grants from the National Institutes of Health and the Novartis/Dana-Farber Cancer Institute Drug Discovery Program (to P. A. S.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵‡ Supported by a National Science Foundation pre-doctoral fellowship and a National Institutes of Health training grant.
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↵§ To whom correspondence should be addressed: Dana-Farber Cancer Inst., Smith 922, 44 Binney St., Boston, MA 02115. Tel.: 617-632-5102; Fax: 617-632-5103; E-mail: pamela_silver{at}dfci.harvard.edu.
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↵2 A. Schroeder, personal communication.
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↵3 J. K. Hood and P. A. Silver, unpublished results.
- Abbreviations:
- NPC
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nuclear pore complex
- NLS
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nuclear localization signal
- GFP
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green fluorescent protein
- PCR
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polymerase chain reaction
- PBS
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phosphate-buffered saline
- GMPPNP
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5′-guanylyl imidodiphosphate
- arm
-
armadillo.
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- Received October 8, 1998.
- Revision received October 29, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
