title: The role of karyopherins in the regulated sumoylation of septins.
abstract: In the yeast Saccharomyces cerevisiae, several components of the septin ring are sumoylated during anaphase and then abruptly desumoylated at cytokinesis. We show that septin sumoylation is controlled by the interactions of two enzymes of the sumoylation pathway, Siz1p and Ulp1p, with the nuclear transport machinery. The E3 ligase Siz1p is imported into the nucleus by the karyopherin Kap95p during interphase. In M phase, Siz1p is exported from the nucleus by the karyopherin Kap142p/Msn5p and subsequently targeted to the septin ring, where it participates in septin sumoylation. We also show that the accumulation of sumoylated septins during mitosis is dependent on the interactions of the SUMO isopeptidase Ulp1p with Kap121p and Kap95p-Kap60p and the nuclear pore complex (NPC). In addition to sequestering Ulp1 at the NPC, Kap121p is required for targeting Ulp1p to the septin ring during mitosis. We present a model in which Ulp1p is maintained at the NPC during interphase and transiently interacts with the septin ring during mitosis.
authors.affiliation: Department of Cell Biology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
authors.forename: Taras
authors.initials: T
authors.lastname: Makhnevych
authors.forename: Christopher
authors.initials: C
authors.lastname: Ptak
authors.forename: C Patrick
authors.initials: CP
authors.lastname: Lusk
authors.forename: John D
authors.initials: JD
authors.lastname: Aitchison
authors.forename: Richard W
authors.initials: RW
authors.lastname: Wozniak
mesh_terms: D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division / Q000502:physiology; D003546:Cysteine Endopeptidases / Q000502:physiology; D028884:Karyopherins / Q000502:physiology*; D008954:Models, Biological; D022022:Nuclear Pore / Q000378:metabolism; D051304:Profilins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism* / Q000502:physiology; D025841:Small Ubiquitin-Related Modifier Proteins / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
chemical_list: C086662:CDC3 protein, S cerevisiae; D018797:Cell Cycle Proteins; D028884:Karyopherins; D051304:Profilins; D029701:Saccharomyces cerevisiae Proteins; D025841:Small Ubiquitin-Related Modifier Proteins; D044767:Ubiquitin-Protein Ligases; D003546:Cysteine Endopeptidases; C118083:Ulp1 protease; C436837:Siz1 protein, S cerevisiae