title: Polarized growth in budding yeast in the absence of a localized formin.
abstract: Polarity is achieved partly through the localized assembly of the cytoskeleton. During growth in budding yeast, the bud cortex and neck localized formins Bni1p and Bnr1p nucleate and assemble actin cables that extend along the bud-mother axis, providing tracks for secretory vesicle delivery. Localized formins are believed to determine the location and polarity of cables, hence growth. However, yeast expressing the nonlocalized actin nucleating/assembly formin homology (FH) 1-FH2 domains of Bnr1p or Bni1p as the sole formin grow well. Although cables are significantly disorganized, analysis of directed transport of secretory vesicles is still biased toward the bud, reflecting a bias in correctly oriented cables, thereby permitting polarized growth. Myosin II, localized at the bud neck, contributes to polarized growth as a mutant unable to interact with F-actin further compromises growth in cells with an unlocalized formin but not with a localized formin. Our results show that multiple mechanisms contribute to cable orientation and polarized growth, with localized formins and myosin II being two major contributors.
authors.affiliation: Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Weill Hall, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Lina
authors.initials: L
authors.lastname: Gao
authors.forename: Anthony
authors.initials: A
authors.lastname: Bretscher
mesh_terms: D000199:Actins / Q000378:metabolism; D016764:Cell Polarity; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism; D050296:Microbial Viability; D008840:Microfilament Proteins / Q000737:chemistry / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000378:metabolism; D024462:Myosin Type II / Q000378:metabolism; D024701:Myosin Type V / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*; D004718:Saccharomycetales / Q000166:cytology* / Q000254:growth & development*; D022142:Secretory Vesicles / Q000378:metabolism
chemical_list: D000199:Actins; C106463:BNR1 protein, S cerevisiae; C105191:Bni1 protein, S cerevisiae; D003598:Cytoskeletal Proteins; C077512:MYO2 protein, S cerevisiae; D008840:Microfilament Proteins; D010446:Peptide Fragments; D029701:Saccharomyces cerevisiae Proteins; D024462:Myosin Type II; D024701:Myosin Type V; D018995:Myosin Heavy Chains