title: IQGAP and mitotic exit network (MEN) proteins are required for cytokinesis and re-polarization of the actin cytoskeleton in the budding yeast, Saccharomyces cerevisiae.
abstract: In budding yeast the final stages of the cell division cycle, cytokinesis and cell separation, are distinct events that require to be coupled, both together and with mitotic exit. Here we demonstrate that mutations in genes of the mitotic exit network (MEN) prevent cell separation and are synthetically lethal in combination with both cytokinesis and septation defective mutations. Analysis of the synthetic lethal phenotypes reveals that Iqg1p functions in combination with the MEN components, Tem1p, Cdc15p Dbf20p and Dbf2p to govern the re-polarization of the actin cytoskeleton to either side of the bud neck. In addition phosphorylation of the conserved PCH protein, Hof1p, is dependent upon these activities and requires actin ring assembly. Recruitment of Dbf2p to the bud neck is dependent upon actin ring assembly and correlates with Hof1p phosphorylation. Failure to phosphorylate Hof1p results in the increased stability of the protein and its persistence at the bud neck. These data establish a mechanistic dependency of cell separation upon an intermediate step requiring actomyosin ring assembly.
authors.affiliation: Biological Sciences, Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK.
authors.forename: Mark
authors.initials: M
authors.lastname: Corbett
authors.forename: Yulan
authors.initials: Y
authors.lastname: Xiong
authors.forename: James R
authors.initials: JR
authors.lastname: Boyne
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Wright
authors.forename: Ewen
authors.initials: E
authors.lastname: Munro
authors.forename: Clive
authors.initials: C
authors.lastname: Price
mesh_terms: D008841:Actin Cytoskeleton / Q000502:physiology* / Q000648:ultrastructure; D000199:Actins / Q000032:analysis; D018797:Cell Cycle Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D048749:Cytokinesis / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D008938:Mitosis / Q000502:physiology; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010641:Phenotype; D010766:Phosphorylation; D011494:Protein Kinases / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D020703:ras GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; C082279:CDC15 protein; D018797:Cell Cycle Proteins; C116847:HOF1 protein, S cerevisiae; C101203:IQ motif containing GTPase activating protein 1; D008869:Microtubule-Associated Proteins; D029701:Saccharomyces cerevisiae Proteins; C089965:TEM1 protein, S cerevisiae; D020703:ras GTPase-Activating Proteins; D011494:Protein Kinases; C085768:DBF2 protein, S cerevisiae; C085769:DBF20 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D019204:GTP-Binding Proteins; D020559:Monomeric GTP-Binding Proteins