title: The putative exchange factor Gef3p interacts with Rho3p GTPase and the septin ring during cytokinesis in fission yeast.
abstract: The small GTP-binding proteins of the Rho family and its regulatory proteins play a central role in cytokinetic actomyosin ring assembly and cytokinesis. Here we show that the fission yeast guanine nucleotide exchange factor Gef3p interacts with Rho3p at the division site. Gef3p contains a putative DH homology domain and a BAR/IMD-like domain. The protein localized to the division site late in mitosis, where it formed a ring that did not constrict with actomyosin ring (cytokinetic actomyosin ring) invagination; instead, it split into a double ring that resembled the septin ring. Gef3p co-localized with septins and Mid2p and required septins and Mid2p for its localization. Gef3p interacts physically with the GTP-bound form of Rho3p. Although Gef3p is not essential for cell separation, the simultaneous disruption of gef3(+) and Rho3p-interacting proteins, such as Sec8p, an exocyst component, Apm1p, a subunit of the clathrin adaptor complex or For3p, an actin-polymerizing protein, yielded cells with strong defects in septation and polarity respectively. Our results suggest that interactions between septins and Rho-GEFs provide a new targeting mechanism for GTPases in cytokinesis, in this case probably contributing to Rho3p function in vesicle tethering and vesicle trafficking in the later steps of cell separation.
authors.affiliation: From the Instituto de Biología Funcional y Genómica (IBFG), Consejo Superior de Investigaciones Científicas and Departamento de Microbiología y Genética, Universidad de Salamanca, C/ Zacarías González, s/n. 37007 Salamanca, Spain.
authors.forename: Sofía
authors.initials: S
authors.lastname: Muñoz
authors.affiliation: From the Instituto de Biología Funcional y Genómica (IBFG), Consejo Superior de Investigaciones Científicas and Departamento de Microbiología y Genética, Universidad de Salamanca, C/ Zacarías González, s/n. 37007 Salamanca, Spain.
authors.forename: Elvira
authors.initials: E
authors.lastname: Manjón
authors.affiliation: From the Instituto de Biología Funcional y Genómica (IBFG), Consejo Superior de Investigaciones Científicas and Departamento de Microbiología y Genética, Universidad de Salamanca, C/ Zacarías González, s/n. 37007 Salamanca, Spain ysm@usal.es.
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Sánchez
mesh_terms: D048749:Cytokinesis / Q000235:genetics / Q000502:physiology; D005800:Genes, Fungal; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D054730:Protein Interaction Domains and Motifs; D055550:Protein Stability; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D064067:Rho Guanine Nucleotide Exchange Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000166:cytology* / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D055571:Secretory Pathway; D058112:Septins / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D020741:rho GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: C000601634:Gef3 protein, S pombe; C516120:MID2 protein, S pombe; D008869:Microtubule-Associated Proteins; D011993:Recombinant Fusion Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; D029702:Schizosaccharomyces pombe Proteins; C489566:rho3 protein, S pombe; D049452:Green Fluorescent Proteins; D058112:Septins; D020741:rho GTP-Binding Proteins
keywords: Cytokinesis; Guanine Nucleotide Exchange Factor (GEF); Morphogenesis; Rho GTPases; Yeast Genetics