title: Enhanced cell polarity in mutants of the budding yeast cyclin-dependent kinase Cdc28p.
abstract: The yeast cyclin-dependent kinase Cdc28p regulates bud morphogenesis and cell cycle progression via the antagonistic activities of Cln and Clb cyclins. Cln G1 cyclins direct polarized growth and bud emergence, whereas Clb G2 cyclins promote isotropic growth of the bud and chromosome segregation. Using colony morphology as a screen to dissect regulation of polarity by Cdc28p, we identified nine point mutations that block the apical-isotropic switch while maintaining other functions. Like a clb2 Delta mutation, each confers tubular bud shape, apically polarized actin distribution, unipolar budding, and delayed anaphase. The mutations are all suppressed by CLB2 overexpression and are synthetically lethal with a CLB2 deletion. However, defects in multiple independent pathways may underlie their common phenotype, because the mutations are scattered throughout the CDC28 sequence, complement each other, and confer diverse biochemical properties. Glu12Gly, a mutation that alters a residue involved in Swe1p inhibition of Cdc28p, was unique in being suppressed by deficiency of SWE1 or CLN1. With wild-type CDC28, filament formation induced by CLN1 overexpression was markedly decreased in a SWE1 deletion. These results suggest that Swe1p, via inhibition of Clb2p/Cdc28p, may mediate much of the effect of Cln1p on filamentous morphogenesis.
authors.affiliation: Center for Molecular Oncology, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: S H
authors.initials: SH
authors.lastname: Ahn
authors.forename: B T
authors.initials: BT
authors.lastname: Tobe
authors.forename: J N
authors.initials: JN
authors.lastname: Fitz Gerald
authors.forename: S L
authors.initials: SL
authors.lastname: Anderson
authors.forename: A
authors.initials: A
authors.lastname: Acurio
authors.forename: S J
authors.initials: SJ
authors.lastname: Kron
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D017489:CDC28 Protein Kinase, S cerevisiae / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D016764:Cell Polarity / Q000502:physiology*; D019926:Cyclin B / Q000235:genetics / Q000378:metabolism; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D005800:Genes, Fungal; D008938:Mitosis; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009024:Morphogenesis; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000254:growth & development / Q000378:metabolism / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins
chemical_list: C093749:CLB2 protein, S cerevisiae; C082719:CLN1 protein, S cerevisiae; D018797:Cell Cycle Proteins; D019926:Cyclin B; D016213:Cyclins; D029701:Saccharomyces cerevisiae Proteins; C099685:SWE1 protein, S cerevisiae; D011505:Protein-Tyrosine Kinases; D017489:CDC28 Protein Kinase, S cerevisiae