title: Hob3p, the fission yeast ortholog of human BIN3, localizes Cdc42p to the division site and regulates cytokinesis.
abstract: Cdc42 GTPase is required for polarization in eukaryotic cells, but its spatial regulation is poorly understood. In Schizosaccharomyces pombe, Cdc42p is activated by Scd1p and Gef1p, two guanine-nucleotide exchange factors. Two-hybrid screening identified Hob3p as a Gef1p binding partner. Hob3p is a BAR domain-containing protein ortholog of human Bin3. Hob3p also interacts directly with Cdc42p independently of Gef1p. Hob3p, Cdc42p and Gef1p form a complex, and Hob3p facilitates Gef1p-Cdc42p interaction and activation. Hob3p forms a ring in the division area, similar to that of Gef1p. This localization requires actin polymerization and Cdc15p but is independent of the septation initiation network. Hob3p is required for the concentration of Cdc42p to the division area. The actomyosin ring contraction is slower in hob3Delta than in wild-type cells, and this contributes to its cytokinesis defect. Moreover, this report extends previous evidence that human Bin3 suppresses the cytokinesis phenotype of hob3Delta cells, showing that Bin3 can partially recover the GTP-Cdc42p level and its localization. These results suggest that Hob3p is required to recruit and activate Cdc42p at the cell division site and that this function might be conserved in other eukaryotes.
authors.affiliation: Consejo Superior de Investigaciones Científicas (CSIC)/Departamento de Microbiología y Genética, Instituto de Microbiología Bioquímica, Universidad de Salamanca, Edificio Departamental, Salamanca 37007, Spain.
authors.forename: Pedro M
authors.initials: PM
authors.lastname: Coll
authors.forename: Sergio A
authors.initials: SA
authors.lastname: Rincon
authors.forename: Raul A
authors.initials: RA
authors.lastname: Izquierdo
authors.forename: Pilar
authors.initials: P
authors.lastname: Perez
mesh_terms: D000199:Actins / Q000378:metabolism; D000205:Actomyosin / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D016764:Cell Polarity; D048749:Cytokinesis; D004789:Enzyme Activation; D008840:Microfilament Proteins / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D012568:Schizosaccharomyces / Q000166:cytology*; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D000199:Actins; C430883:BIN3 protein, human; D002352:Carrier Proteins; C519557:Hob3p protein, S pombe; D008840:Microfilament Proteins; D029702:Schizosaccharomyces pombe Proteins; D000205:Actomyosin; D020764:cdc42 GTP-Binding Protein