title: Localization of the Rsr1/Bud1 GTPase involved in selection of a proper growth site in yeast.
abstract: Yeast cells organize their actin cytoskeleton in a highly polarized manner during vegetative growth. The Ras-like GTPase Rsr1/Bud1 and its regulators are required for selection of a specific site for growth. Here we showed that Rsr1/Bud1 was broadly distributed on the plasma membrane and highly concentrated at the incipient bud site and polarized growth sites. We also showed that localization of Cdc24, a guanine nucleotide exchange factor for the Cdc42 GTPase, to the proper bud site was dependent on Rsr1/Bud1. Surprisingly, Rsr1/Bud1 also localized to intracellular membranes. A mutation in the lysine repeat in the hypervariable region of Rsr1/Bud1 specifically abolished its plasma membrane localization, whereas a mutation at the CAAX motif eliminated both plasma membrane and internal membrane association of Rsr1/Bud1. Thus the lysine repeat and the CAAX motif of Rsr1/Bud1 are important for its localization to the plasma membrane and to the polarized growth sites. This localization of Rsr1/Bud1 is essential for its function in proper bud site selection because both mutations resulted in random bud site selection.
authors.affiliation: Graduate Program in Molecular, Cellular, and Developmental Biology, Department of Molecular Genetics, The Ohio State University, 484 West 12th Avenue, Columbus, OH 43210-1292, USA. park.294@osu.edu
authors.forename: Hay-Oak
authors.initials: HO
authors.lastname: Park
authors.forename: Pil Jung
authors.initials: PJ
authors.lastname: Kang
authors.forename: Amy Wilson
authors.initials: AW
authors.lastname: Rachfal
mesh_terms: D020816:Amino Acid Motifs; D018797:Cell Cycle Proteins / Q000096:biosynthesis; D002455:Cell Division; D002462:Cell Membrane / Q000378:metabolism; D016193:G1 Phase; D049452:Green Fluorescent Proteins; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D008164:Luminescent Proteins / Q000378:metabolism; D008239:Lysine / Q000737:chemistry; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011003:Ploidies; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D015398:Signal Transduction; D014617:Vacuoles / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000096:biosynthesis*
chemical_list: C073594:CDC24 protein, S cerevisiae; D018797:Cell Cycle Proteins; D020662:Guanine Nucleotide Exchange Factors; D008164:Luminescent Proteins; D011518:Proto-Oncogene Proteins; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins; C084013:RSR1 protein, S cerevisiae; D020691:rab GTP-Binding Proteins; D008239:Lysine