title: The Ran GTPase system in fission yeast affects microtubules and cytokinesis in cells that are competent for nucleocytoplasmic protein transport.
abstract: Misregulation of the evolutionarily conserved GTPase Ran in fission yeast results in defects in several cellular processes in cells that are competent for nucleocytoplasmic protein transport. These results suggest that transport is neither the only nor the primary Ran-dependent process in living cells. The ability of Ran to independently regulate multiple cellular processes in vivo is demonstrated by showing that (i) eight different transport-competent RanGEF (guanine nucleotide exchange factor) mutants have defects in mitotic spindle formation; (ii) the RanGEF temperature-sensitive mutant pim1-d1 has abnormal actin ring structures at the septum. Overexpression of Imp2p, which specifically destabilizes these structures, restores viability. (iii) Ran-dependent processes differ in their requirements for active Ran in vivo. Microtubule function, cytokinesis, and nuclear envelope structure are the Ran-dependent processes most sensitive to the amount of Ran protein in the cell, whereas nucleocytoplasmic protein transport is the most robust. Therefore, the ability of Ran from Schizosaccharomyces pombe to independently regulate multiple cellular processes may reflect differences in its interactions with the binding proteins that mediate these functions and explain the complex phenotypic consequences of its misregulation in vivo.
authors.affiliation: Interdepartmental Program in Cell and Molecular Biology, Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
authors.forename: Sandra S
authors.initials: SS
authors.lastname: Salus
authors.forename: Janos
authors.initials: J
authors.lastname: Demeter
authors.forename: Shelley
authors.initials: S
authors.lastname: Sazer
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D002453:Cell Cycle / Q000502:physiology; D002455:Cell Division / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D010450:Endopeptidases / Q000378:metabolism; D005800:Genes, Fungal; D018816:Genes, cdc; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism*; D009154:Mutation; D010641:Phenotype; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D012568:Schizosaccharomyces / Q000166:cytology / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*; D008941:Spindle Apparatus / Q000378:metabolism; D013827:Thiabendazole / Q000494:pharmacology; D020931:ran GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D010450:Endopeptidases; D020931:ran GTP-Binding Protein; D013827:Thiabendazole