title: Evidence for functional links between the Rgd1-Rho3 RhoGAP-GTPase module and Tos2, a protein involved in polarized growth in Saccharomyces cerevisiae.
abstract: The Rho GTPase-activating protein Rgd1p positively regulates the GTPase activity of Rho3p and Rho4p, which are involved in bud growth and cytokinesis, respectively, in the budding yeast Saccharomyces cerevisiae. Two-hybrid screening identified Tos2p as a candidate Rgd1p-binding protein. Further analyses confirmed that Tos2p binds to the RhoGAP Rgd1p through its C-terminal region. Both Tos2p and Rgd1p are localized to polarized growth sites during the cell cycle and associated with detergent-resistant membranes. We observed that TOS2 overexpression suppressed rgd1Δ sensitivity to a low pH. In the tos2Δ strain, the amount of GTP-bound Rho3p was increased, suggesting an influence of Tos2p on Rgd1p activity in vivo. We also showed a functional interaction between the TOS2 and the RHO3 genes: TOS2 overexpression partially suppressed the growth defect of rho3-V51 cells at a restrictive temperature. We propose that Tos2p, a protein involved in polarized growth and most probably associated with the plasma membrane, modulates the action of Rgd1p and Rho3p in S. cerevisiae.
authors.affiliation: RDPR, Institute of Cellular Biochemistry and Genetics, University of Bordeaux 2, Bordeaux, France.
authors.forename: Sandra
authors.initials: S
authors.lastname: Claret
authors.forename: Olivier
authors.initials: O
authors.lastname: Roumanie
authors.forename: Valérie
authors.initials: V
authors.lastname: Prouzet-Mauleon
authors.forename: Fabien
authors.initials: F
authors.lastname: Lefebvre
authors.forename: Didier
authors.initials: D
authors.lastname: Thoraval
authors.forename: Marc
authors.initials: M
authors.lastname: Crouzet
authors.forename: François
authors.initials: F
authors.lastname: Doignon
mesh_terms: D018797:Cell Cycle Proteins / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D017353:Gene Deletion; D011485:Protein Binding; D025941:Protein Interaction Mapping; D011494:Protein Kinases / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000254:growth & development* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D020690:GTPase-Activating Proteins; C449479:RGD1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C558448:Tos2 protein, S cerevisiae; C085379:rho GTPase-activating protein; D011494:Protein Kinases; D020558:GTP Phosphohydrolases; C074647:RHO3 protein, S cerevisiae; D020741:rho GTP-Binding Proteins