title: Interaction between a Ras and a Rho GTPase couples selection of a growth site to the development of cell polarity in yeast.
abstract: Polarized cell growth requires the coupling of a defined spatial site on the cell cortex to the apparatus that directs the establishment of cell polarity. In the budding yeast Saccharomyces cerevisiae, the Ras-family GTPase Rsr1p/Bud1p and its regulators select the proper site for bud emergence on the cell cortex. The Rho-family GTPase Cdc42p and its associated proteins then establish an axis of polarized growth by triggering an asymmetric organization of the actin cytoskeleton and secretory apparatus at the selected bud site. We explored whether a direct linkage exists between the Rsr1p/Bud1p and Cdc42p GTPases. Here we show specific genetic interactions between RSR1/BUD1 and particular cdc42 mutants defective in polarity establishment. We also show that Cdc42p coimmunoprecipitated with Rsr1p/Bud1p from yeast extracts. In vitro studies indicated a direct interaction between Rsr1p/Bud1p and Cdc42p, which was enhanced by Cdc24p, a guanine nucleotide exchange factor for Cdc42p. Our findings suggest that Cdc42p interacts directly with Rsr1p/Bud1p in vivo, providing a novel mechanism by which direct contact between a Ras-family GTPase and a Rho-family GTPase links the selection of a growth site to polarity establishment.
authors.affiliation: Departments of Biology and Cell Biology, University of Virginia, Charlottesville, Virginia 22904, USA.
authors.forename: Keith G
authors.initials: KG
authors.lastname: Kozminski
authors.forename: Laure
authors.initials: L
authors.lastname: Beven
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Angerman
authors.forename: Amy Hin Yan
authors.initials: AH
authors.lastname: Tong
authors.forename: Charles
authors.initials: C
authors.lastname: Boone
authors.forename: Hay-Oak
authors.initials: HO
authors.lastname: Park
mesh_terms: D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D016764:Cell Polarity / Q000502:physiology*; D003001:Cloning, Molecular; D020662:Guanine Nucleotide Exchange Factors; D008958:Models, Molecular; D011485:Protein Binding; D017434:Protein Structure, Tertiary / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C073594:CDC24 protein, S cerevisiae; D018797:Cell Cycle Proteins; D020662:Guanine Nucleotide Exchange Factors; D011518:Proto-Oncogene Proteins; D029701:Saccharomyces cerevisiae Proteins; C084013:RSR1 protein, S cerevisiae; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae; D020691:rab GTP-Binding Proteins