title: Bud3 activates Cdc42 to establish a proper growth site in budding yeast.
abstract: Cell polarization occurs along a single axis that is generally determined by a spatial cue, yet the underlying mechanism is poorly understood. Using biochemical assays and live-cell imaging, we show that cell polarization to a proper growth site requires activation of Cdc42 by Bud3 in haploid budding yeast. Bud3 catalyzes the release of guanosine diphosphate (GDP) from Cdc42 and elevates intracellular Cdc42-guanosine triphosphate (GTP) levels in cells with inactive Cdc24, which has as of yet been the sole GDP-GTP exchange factor for Cdc42. Cdc42 is activated in two temporal steps in the G1 phase: the first depends on Bud3, whereas subsequent activation depends on Cdc24. Mutational analyses suggest that biphasic activation of Cdc42 in G1 is necessary for assembly of a proper bud site. Biphasic activation of Cdc42 or Rac GTPases may be a general mechanism for spatial cue-directed cell polarization in eukaryotes.
authors.affiliation: Department of Molecular Genetics and Molecular Cellular Developmental Biology Program, The Ohio State University, Columbus, OH 43210.
authors.forename: Pil Jung
authors.initials: PJ
authors.lastname: Kang
authors.affiliation: Department of Molecular Genetics and Molecular Cellular Developmental Biology Program, The Ohio State University, Columbus, OH 43210.
authors.forename: Mid Eum
authors.initials: ME
authors.lastname: Lee
authors.affiliation: Department of Molecular Genetics and Molecular Cellular Developmental Biology Program, The Ohio State University, Columbus, OH 43210Department of Molecular Genetics and Molecular Cellular Developmental Biology Program, The Ohio State University, Columbus, OH 43210 park.294@osu.edu.
authors.forename: Hay-Oak
authors.initials: HO
authors.lastname: Park
mesh_terms: D000595:Amino Acid Sequence; D002455:Cell Division; D016764:Cell Polarity; D004789:Enzyme Activation; D059585:G1 Phase Cell Cycle Checkpoints; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000502:physiology*; D059008:Time-Lapse Imaging; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / Q000378:metabolism*
chemical_list: C093319:BUD3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae