title: Cse1p is required for export of Srp1p/importin-alpha from the nucleus in Saccharomyces cerevisiae.
abstract: In metazoan cells, the CAS protein has been shown to function as a recycling factor for the importin-alpha subunit of the classical nuclear localization signal receptor, exporting importin-alpha 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-beta, and that are found in all eukaryotes from yeast to humans. Sequence similarity identifies the product of the Saccharomyces 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-alpha in the nucleus, it localizes to the nuclear envelope in a pattern typical of nuclear transport receptors, and it associates in 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.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, and the Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA.
authors.forename: J K
authors.initials: JK
authors.lastname: Hood
authors.forename: P A
authors.initials: PA
authors.lastname: Silver
mesh_terms: D001692:Biological Transport; D002451:Cell Compartmentation; D002467:Cell Nucleus / Q000378:metabolism*; D029563:Cellular Apoptosis Susceptibility Protein; D005656:Fungal Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D028884:Karyopherins; D008164:Luminescent Proteins / Q000235:genetics / Q000302:isolation & purification; D009685:Nuclear Envelope / Q000737:chemistry; D009687:Nuclear Proteins / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins; D011233:Precipitin Tests; D011485:Protein Binding; D011506:Proteins; D011993:Recombinant Fusion Proteins / Q000302:isolation & purification / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D028901:alpha Karyopherins
chemical_list: C082274:CSE1 protein, S cerevisiae; D029563:Cellular Apoptosis Susceptibility Protein; D005656:Fungal Proteins; D028884:Karyopherins; D008164:Luminescent Proteins; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D011506:Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D028901:alpha Karyopherins; D049452:Green Fluorescent Proteins