title: Fission yeast myosin-I, Myo1p, stimulates actin assembly by Arp2/3 complex and shares functions with WASp.
abstract: Fission yeast myo1(+) encodes a myosin-I with all three tail homology domains (TH1, 2, 3) found in typical long-tailed myosin-Is. Myo1p tail also contains a COOH-terminal acidic region similar to the A-domain of WASp/Scar proteins and other fungal myosin-Is. Our analysis shows that Myo1p and Wsp1p, the fission yeast WASp-like protein, share functions and cooperate in controlling actin assembly. First, Myo1p localizes to cortical patches enriched at tips of growing cells and at sites of cell division. Myo1p patches partially colocalize with actin patches and are dependent on an intact actin cytoskeleton. Second, although deletion of myo1(+) is not lethal, Deltamyo1 cells have actin cytoskeletal defects, including loss of polarized cell growth, delocalized actin patches, and mating defects. Third, additional disruption of wsp1(+) is synthetically lethal, suggesting that these genes may share functions. In mapping the domains of Myo1p tail that share function with Wsp1p, we discovered that a Myo1p construct with just the head and TH1 domains is sufficient for cortical localization and to rescue all Deltamyo1 defects. However, it fails to rescue the Deltamyo1 Deltawsp1 lethality. Additional tail domains, TH2 and TH3, are required to complement the double mutant. Fourth, we show that a recombinant Myo1p tail binds to Arp2/3 complex and activates its actin nucleation activity.
authors.affiliation: Graduate Program in Biochemistry, Cellular and Molecular Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
authors.forename: W L
authors.initials: WL
authors.lastname: Lee
authors.forename: M
authors.initials: M
authors.lastname: Bezanilla
authors.forename: T D
authors.initials: TD
authors.lastname: Pollard
mesh_terms: D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002148:Calmodulin-Binding Proteins; D002455:Cell Division; D003001:Cloning, Molecular; D003598:Cytoskeletal Proteins; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005816:Genetic Complementation Test; D005838:Genotype; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism*; D024461:Myosin Type I; D011993:Recombinant Fusion Proteins / Q000032:analysis; D011994:Recombinant Proteins / Q000378:metabolism; D015183:Restriction Mapping; D012568:Schizosaccharomyces / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D029702:Schizosaccharomyces pombe Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: C495926:ACTR2 protein, human; C495928:ACTR3 protein, human; D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins; D002148:Calmodulin-Binding Proteins; D003598:Cytoskeletal Proteins; D005656:Fungal Proteins; C062291:MYO1A protein, human; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D029702:Schizosaccharomyces pombe Proteins; C417034:Wsp1 protein, S pombe; C491828:myo1 protein, S pombe; D024461:Myosin Type I; D018995:Myosin Heavy Chains