title: The Cdc42p GTPase is involved in a G2/M morphogenetic checkpoint regulating the apical-isotropic switch and nuclear division in yeast.
abstract: The Cdc42p GTPase is involved in the signal transduction cascades controlling bud emergence and polarized cell growth in S. cerevisiae. Cells expressing the cdc42(V44A) effector domain mutant allele displayed morphological defects of highly elongated and multielongated budded cells indicative of a defect in the apical-isotropic switch in bud growth. In addition, these cells contained one, two, or multiple nuclei indicative of a G2/M delay in nuclear division and also a defect in cytokinesis and/or cell separation. Actin and chitin were delocalized, and septin ring structure was aberrant and partially delocalized to the tips of elongated cdc42(V44A) cells; however, Cdc42(V44A)p localization was normal. Two-hybrid protein analyses showed that the V44A mutation interfered with Cdc42p's interactions with Cla4p, a p21(Cdc42/Rac)-activated kinase (PAK)-like kinase, and the novel effectors Gic1p and Gic2p, but not with the Ste20p or Skm1p PAK-like kinases, the Bni1p formin, or the Iqg1p IQGAP homolog. Furthermore, the cdc42(V44A) morphological defects were suppressed by deletion of the Swe1p cyclin-dependent kinase inhibitory kinase and by overexpression of Cla4p, Ste20p, the Cdc12 septin protein, or the guanine nucleotide exchange factor Cdc24p. In sum, these results suggest that proper Cdc42p function is essential for timely progression through the apical-isotropic switch and G2/M transition and that Cdc42(V44A)p differentially interacts with a number of effectors and regulators.
authors.affiliation: Department of Microbiology and Molecular Genetics and the Markey Center for Molecular Genetics, University of Vermont, Burlington, Vermont 05405, USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Richman
authors.forename: M M
authors.initials: MM
authors.lastname: Sawyer
authors.forename: D I
authors.initials: DI
authors.lastname: Johnson
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002455:Cell Division; D002467:Cell Nucleus / Q000502:physiology*; D016764:Cell Polarity; D002686:Chitin / Q000302:isolation & purification; D003598:Cytoskeletal Proteins; D005656:Fungal Proteins / Q000302:isolation & purification; D016195:G2 Phase; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D020930:MAP Kinase Kinase Kinases; D008938:Mitosis; D009024:Morphogenesis; D009154:Mutation; D051304:Profilins; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology*; D029701:Saccharomyces cerevisiae Proteins; D013489:Suppression, Genetic; D013997:Time Factors; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C099504:CDC12 protein, S cerevisiae; C086662:CDC3 protein, S cerevisiae; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; D005656:Fungal Proteins; C109252:GIC1 protein, S cerevisiae; C109253:GIC2 protein, S cerevisiae; D047908:Intracellular Signaling Peptides and Proteins; D051304:Profilins; D029701:Saccharomyces cerevisiae Proteins; D002686:Chitin; D011494:Protein Kinases; C099685:SWE1 protein, S cerevisiae; D011505:Protein-Tyrosine Kinases; C095212:CLA4 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D020930:MAP Kinase Kinase Kinases; C078754:STE20 protein, S cerevisiae; D019204:GTP-Binding Proteins; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae