title: Roles of an N-terminal coiled-coil-containing domain in the localization and function of Bem3, a Rho GTPase-activating protein in budding yeast.
abstract: GTPase-activating proteins (GAPs) play critical roles in the spatial and temporal control of small GTPases. The budding yeast Bem3 is a GAP for Cdc42, a Rho GTPase crucial for actin and septin organization. Bem3 localizes to the sites of polarized growth. However, the amino acid sequence determinants mediating recruitment of Bem3 to its physiological sites of action and those important for Bem3 function are not clear. Here, we show that Bem3's localization is guided by two distinct targeting regions-the PX-PH-domain-containing TD1 and the coiled-coil-containing TD2. TD2 localization is largely mediated by its interaction with the polarisome component Epo1 via heterotypic coiled-coil interaction. This finding reveals a novel role for the polarisome in linking Bem3 to its functional target, Cdc42. We also show that the coiled-coil domain of Bem3 interacts homotypically and this interaction is important for the regulation of Cdc42 by Bem3. Moreover, we show that overexpression of a longer version of the TD2 domain disrupts septin-ring assembly in a RhoGAP-independent manner, suggesting that TD2 may be capable of interacting with proteins implicated in septin-ring assembly. Furthermore, we show that the longer version of TD2 interacts with Kss1, a MAPK involved in filamentous growth. Kss1 is reported to localize mainly in the nucleus. We find that Kss1 also localizes to the sites of polarized growth and Bem3 interacts with Kss1 at the septin-ring assembly site. Our study provides new insights in Bem3's localization and function.
authors.affiliation: Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China.
authors.forename: Wen-Chao
authors.initials: WC
authors.lastname: Nie
authors.affiliation: Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China.
authors.forename: Fei
authors.initials: F
authors.lastname: He
authors.affiliation: Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China.
authors.forename: Si-Min
authors.initials: SM
authors.lastname: Yuan
authors.affiliation: Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China.
authors.forename: Zhi-Wen
authors.initials: ZW
authors.lastname: Jia
authors.affiliation: Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China.
authors.forename: Rui-Rui
authors.initials: RR
authors.lastname: Wang
authors.affiliation: Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China; Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Wuhan, China. Electronic address: xdgao@whu.edu.cn.
authors.forename: Xiang-Dong
authors.initials: XD
authors.lastname: Gao
mesh_terms: D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D016764:Cell Polarity / Q000235:genetics; D020690:GTPase-Activating Proteins / Q000235:genetics* / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics* / Q000378:metabolism; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D058112:Septins / Q000235:genetics / Q000378:metabolism; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism
chemical_list: C084220:BEM3 protein, S cerevisiae; D002352:Carrier Proteins; C000594941:Epo1 protein, S cerevisiae; D020690:GTPase-Activating Proteins; D029701:Saccharomyces cerevisiae Proteins; C541984:KSS1 protein, S cerevisiae; D020928:Mitogen-Activated Protein Kinases; D058112:Septins; D020559:Monomeric GTP-Binding Proteins; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae
keywords: Bem3; Cdc42; Kss1; Polarized growth; RhoGAP; Septin