title: Tension modulates actin filament polymerization mediated by formin and profilin.
abstract: Formins promote processive elongation of actin filaments for cytokinetic contractile rings and other cellular structures. In vivo, these structures are exposed to tension, but the effect of tension on these processes was unknown. Here we used single-molecule imaging to investigate the effects of tension on actin polymerization mediated by yeast formin Bni1p. Small forces on the filaments dramatically slowed formin-mediated polymerization in the absence of profilin, but resulted in faster polymerization in the presence of profilin. We propose that force shifts the conformational equilibrium of the end of a filament associated with formin homology 2 domains toward the closed state that precludes polymerization, but that profilin-actin associated with formin homology 1 domains reverses this effect. Thus, physical forces strongly influence actin assembly by formin Bni1p.
authors.affiliation: Departments of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520-8103, USA. thomas.pollard@yale.edu
authors.forename: Naomi
authors.initials: N
authors.lastname: Courtemanche
authors.forename: Ja Yil
authors.initials: JY
authors.lastname: Lee
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Pollard
authors.forename: Eric C
authors.initials: EC
authors.lastname: Greene
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry / Q000378:metabolism*; D000465:Algorithms; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008840:Microfilament Proteins / Q000737:chemistry / Q000378:metabolism*; D008954:Models, Biological; D008958:Models, Molecular; D008968:Molecular Conformation; D058105:Polymerization; D051304:Profilins / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*; D013314:Stress, Mechanical; D013997:Time Factors
chemical_list: C105191:Bni1 protein, S cerevisiae; C086662:CDC3 protein, S cerevisiae; D018797:Cell Cycle Proteins; D008840:Microfilament Proteins; D051304:Profilins; D029701:Saccharomyces cerevisiae Proteins