The Rsr1/Bud1 GTPase interacts with itself and the Cdc42 GTPase during bud-site selection and polarity establishment in budding yeast.
Cell polarization occurs along a single axis that is generally determined in response to spatial cues. In budding yeast, the Rsr1 GTPase and its regulators direct the establishment of cell polarity at the proper cortical location in response to cell type-specific cues. Here we use a combination of in vivo and in vitro approaches to understand how Rsr1 polarization is established. We find that Rsr1 associates with itself in a spatially and temporally controlled manner. The homotypic interaction and localization of Rsr1 to the mother-bud neck and to the subsequent division site are dependent on its GDP-GTP exchange factor Bud5. Analyses of rsr1 mutants suggest that Bud5 recruits Rsr1 to these sites and promotes the homodimer formation. Rsr1 also exhibits heterotypic interaction with the Cdc42 GTPase in vivo. We show that the polybasic region of Rsr1 is necessary for the efficient homotypic and heterotypic interactions, selection of a proper growth site, and polarity establishment. Our findings thus suggest that dimerization of GTPases may be an efficient mechanism to set up cellular asymmetry.
Kang
Pil Jung
PJ
Department of Molecular Genetics and the Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA.
Béven
Laure
L
Hariharan
Seethalakshmi
S
Park
Hay-Oak
HO
D000595:Amino Acid Sequence; D002455:Cell Division; D002467:Cell Nucleus / Q000378:metabolism; D016764:Cell Polarity; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D055503:Protein Multimerization; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*
C091391:BUD5 protein, S cerevisiae; D020662:Guanine Nucleotide Exchange Factors; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; C084013:RSR1 protein, S cerevisiae; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae; D020691:rab GTP-Binding Proteins