title: The yeast nuclear import receptor is required for mitosis.
abstract: The nuclear import system is highly conserved among eukaryotes. Here we report the effects of a conditional mutation in SRP1, which encodes a Saccharomyces cerevisiae homolog of the vertebrate nuclear import receptor importin. Importin was isolated as a factor required for the initial targeting step of a nuclear import substrate to the nuclear envelope in a mammalian in vitro assay. We show that yeast Srp1 is similarly required for protein import. In addition, Srp1 is also required for the execution of mitosis: we demonstrate that cells containing a conditional mutation of SRP1 arrest with a G2/M phenotype in a manner analogous to classic cdc mutants. This defect may be due to the failure of the mutant to degrade the mitotic cyclin Clb2 and other proteins required for mitosis. The requirement of a nuclear import receptor for cell cycle-regulated proteolysis implies that import of cell cycle regulators into the nucleus is critical for cell cycle progression.
authors.affiliation: Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology, Cambridge 02142, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Loeb
authors.forename: G
authors.initials: G
authors.lastname: Schlenstedt
authors.forename: D
authors.initials: D
authors.lastname: Pellman
authors.forename: D
authors.initials: D
authors.lastname: Kornitzer
authors.forename: P A
authors.initials: PA
authors.lastname: Silver
authors.forename: G R
authors.initials: GR
authors.lastname: Fink
mesh_terms: D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000502:physiology*; D017931:DNA Primers; D005800:Genes, Fungal; D005804:Genes, Lethal; D005838:Genotype; D028884:Karyopherins; D000072235:Mating Factor; D008938:Mitosis; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D010675:Pheromones / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D014714:Vertebrates; D028901:alpha Karyopherins
chemical_list: D017931:DNA Primers; D028884:Karyopherins; D009687:Nuclear Proteins; D010455:Peptides; D010675:Pheromones; D011993:Recombinant Fusion Proteins; D028901:alpha Karyopherins; D000072235:Mating Factor