Pob1 participates in the Cdc42 regulation of fission yeast actin cytoskeleton.
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.
Rincón
Sergio A
SA
Instituto de Microbiología Bioquímica, Consejo Superior de Investigaciones Científicas/Departamento de Microbiología y Genética, Universidad de Salamanca, 37007 Salamanca, Spain.
Ye
Yanfang
Y
Villar-Tajadura
M Antonia
MA
Santos
Beatriz
B
Martin
Sophie G
SG
Pérez
Pilar
P
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*
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