title: The GTPase-activating protein Rga1 interacts with Rho3 GTPase and may regulate its function in polarized growth in budding yeast.
abstract: In budding yeast, Rga1 negatively regulates the Rho GTPase Cdc42 by acting as a GTPase-activating protein (GAP) for Cdc42. To gain insight into the function and regulation of Rga1, we overexpressed Rga1 and an N-terminally truncated Rga1-C538 (a.a. 538-1007) segment. Overexpression of Rga1-C538 but not full-length Rga1 severely impaired growth and cell morphology in wild-type cells. We show that Rga1 is phosphorylated during the cell cycle. The lack of phenotype for full-length Rga1 upon overexpression may result from a negative regulation by G1-specific Pho85, a cyclin-dependent kinase (CDK). From a high-copy suppressor screen, we isolated RHO3, SEC9, SEC1, SSO1, SSO2, and SRO7, genes involved in exocytosis, as suppressors of the growth defect caused by Rga1-C538 overexpression. Moreover, we detected that Rga1 interacts with Rho3 in two-hybrid and bimolecular fluorescence complementation (BiFC) assays. Rga1 preferentially interacts with the GTP-bound form of Rho3 and the interaction requires the GAP domain and additional sequence upstream of the GAP domain. Our data suggest that the interaction of Rga1 with Rho3 may regulate Rho3's function in polarized bud growth.
authors: Department of Microbiology, College of Life Sciences, Wuhan University, Wuhan, China.
authors: Fei
authors: F
authors: He
authors: Department of Microbiology, College of Life Sciences, Wuhan University, Wuhan, China.
authors: Wen-Chao
authors: WC
authors: Nie
authors: Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, United States of America.
authors: Zongtian
authors: Z
authors: Tong
authors: Department of Microbiology, College of Life Sciences, Wuhan University, Wuhan, China.
authors: Si-Min
authors: SM
authors: Yuan
authors: Department of Microbiology, College of Life Sciences, Wuhan University, Wuhan, China.
authors: Ting
authors: T
authors: Gong
authors: Department of Microbiology, College of Life Sciences, Wuhan University, Wuhan, China.
authors: Yuan
authors: Y
authors: Liao
authors: Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, United States of America.
authors: Erfei
authors: E
authors: Bi
authors: Department of Microbiology, College of Life Sciences, Wuhan University, Wuhan, China; Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Wuhan, China.
authors: Xiang-Dong
authors: XD
authors: Gao
mesh_terms: D005089:Exocytosis; D020690:GTPase-Activating Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D010641:Phenotype; D010766:Phosphorylation; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs / Q000235:genetics; D004718:Saccharomycetales / Q000502:physiology*; D020741:rho GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D020690:GTPase-Activating Proteins; D020741:rho GTP-Binding Proteins