title: The Rho-GEF Gef3 interacts with the septin complex and activates the GTPase Rho4 during fission yeast cytokinesis.
abstract: Rho GTPases, activated by Rho guanine nucleotide exchange factors (GEFs), are conserved molecular switches for signal transductions that regulate diverse cellular processes, including cell polarization and cytokinesis. The fission yeast Schizosaccharomyces pombe has six Rho GTPases (Cdc42 and Rho1-Rho5) and seven Rho GEFs (Scd1, Rgf1-Rgf3, and Gef1-Gef3). The GEFs for Rho2-Rho5 have not been unequivocally assigned. In particular, Gef3, the smallest Rho GEF, was barely studied. Here we show that Gef3 colocalizes with septins at the cell equator. Gef3 physically interacts with septins and anillin Mid2 and depends on them to localize. Gef3 coprecipitates with GDP-bound Rho4 in vitro and accelerates nucleotide exchange of Rho4, suggesting that Gef3 is a GEF for Rho4. Consistently, Gef3 and Rho4 are in the same genetic pathways to regulate septum formation and/or cell separation. In gef3∆ cells, the localizations of two potential Rho4 effectors--glucanases Eng1 and Agn1--are abnormal, and active Rho4 level is reduced, indicating that Gef3 is involved in Rho4 activation in vivo. Moreover, overexpression of active Rho4 or Eng1 rescues the septation defects of mutants containing gef3∆. Together our data support that Gef3 interacts with the septin complex and activates Rho4 GTPase as a Rho GEF for septation in fission yeast.
authors.affiliation: Department of Molecular Genetics.
authors.forename: Ning
authors.initials: N
authors.lastname: Wang
authors.affiliation: Department of Molecular Genetics.
authors.forename: Mo
authors.initials: M
authors.lastname: Wang
authors.affiliation: Department of Molecular Genetics.
authors.forename: Yi-Hua
authors.initials: YH
authors.lastname: Zhu
authors.affiliation: Department of Molecular Genetics.
authors.forename: Timothy W
authors.initials: TW
authors.lastname: Grosel
authors.affiliation: Department of Molecular Genetics.
authors.forename: Daokun
authors.initials: D
authors.lastname: Sun
authors.affiliation: Department of Chemistry and Biochemistry.
authors.forename: Dmitri S
authors.initials: DS
authors.lastname: Kudryashov
authors.affiliation: Department of Molecular Genetics Department of Molecular and Cellular Biochemistry, The Ohio State University, Columbus, OH 43210 wu.620@osu.edu.
authors.forename: Jian-Qiu
authors.initials: JQ
authors.lastname: Wu
mesh_terms: D015153:Blotting, Western; D002455:Cell Division; D048749:Cytokinesis; D036681:Fluorescence Recovery After Photobleaching; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D009154:Mutation; D011485:Protein Binding; D064067:Rho Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*; D058112:Septins / Q000235:genetics / Q000378:metabolism*
chemical_list: C000601634:Gef3 protein, S pombe; C506338:RHO4 protein, S pombe; D064067:Rho Guanine Nucleotide Exchange Factors; D029702:Schizosaccharomyces pombe Proteins; D049452:Green Fluorescent Proteins; D006026:Glycoside Hydrolases; C511866:Agn1 protein, S pombe; D019204:GTP-Binding Proteins; D058112:Septins