title: Pob1 participates in the Cdc42 regulation of fission yeast actin cytoskeleton.
abstract: Rho GTPases regulate the actin cytoskeleton in all eukaryotes. Fission yeast Cdc42 is involved in actin cable assembly and formin For3 regulation. We isolated cdc42-879 as a thermosensitive strain with actin cable and For3 localization defects. In a multicopy suppressor screening, we identified pob1(+) as suppressor of cdc42-879 thermosensitivity. Pob1 overexpression also partially restores actin cables and localization of For3 in the mutant strain. Pob1 interacts with Cdc42 and this GTPase regulates Pob1 localization and/or stability. The C-terminal pleckstrin homology (PH) domain of Pob1 is required for Cdc42 binding. Pob1 also binds to For3 through its N-terminal sterile alpha motif (SAM) domain and contributes to the formin localization at the cell tips. The previously described pob1-664 mutant strain (Mol. Biol. Cell. 10, 2745-2757, 1999), which carries a mutation in the PH domain, as well as pob1 mutant strains in which Pob1 lacks the N-terminal region (pob1DeltaN) or the SAM domain (pob1DeltaSAM), have cytoskeletal defects similar to that of cdc42-879 cells. Expression of constitutively active For3DAD* partially restores actin organization in cdc42-879, pob1-664, pob1DeltaN, and pob1DeltaSAM. Therefore, we propose that Pob1 is required for For3 localization to the tips and facilitates Cdc42-mediated relief of For3 autoinhibition to stimulate actin cable formation.
authors.affiliation: Instituto de Microbiología Bioquímica, Consejo Superior de Investigaciones Científicas/Departamento de Microbiología y Genética, Universidad de Salamanca, 37007 Salamanca, Spain.
authors.forename: Sergio A
authors.initials: SA
authors.lastname: Rincón
authors.forename: Yanfang
authors.initials: Y
authors.lastname: Ye
authors.forename: M Antonia
authors.initials: MA
authors.lastname: Villar-Tajadura
authors.forename: Beatriz
authors.initials: B
authors.lastname: Santos
authors.forename: Sophie G
authors.initials: SG
authors.lastname: Martin
authors.forename: Pilar
authors.initials: P
authors.lastname: Pérez
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure*; D000199:Actins / Q000378:metabolism; D019943:Amino Acid Substitution; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000502:physiology; D016764:Cell Polarity; D003599:Cytoskeleton / Q000648:ultrastructure*; D000080865:Formins; D015966:Gene Expression Regulation, Fungal; D006160:Guanosine Triphosphate / Q000502:physiology; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D012568:Schizosaccharomyces / Q000378:metabolism* / Q000648:ultrastructure; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D020764:cdc42 GTP-Binding Protein / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D020741:rho GTP-Binding Proteins / Q000737:chemistry / Q000502:physiology*
chemical_list: D000199:Actins; D018797:Cell Cycle Proteins; C444419:FOR3 protein, S pombe; D000080865:Formins; D029702:Schizosaccharomyces pombe Proteins; D006160:Guanosine Triphosphate; C548057:Pob1 protein, S pombe; D020764:cdc42 GTP-Binding Protein; D020741:rho GTP-Binding Proteins