title: The functionally distinct fission yeast formins have specific actin-assembly properties.
abstract: Fission yeast expresses three formins required for distinct actin cytoskeletal processes: Cdc12 (cytokinesis), For3 (polarization), and Fus1 (mating). We propose that in addition to differential regulation, key actin-assembly properties tailor formins for a particular role. In direct comparison to the well-studied Cdc12, we report the first in vitro characterization of the actin-assembly properties of For3 and Fus1. All three share fundamental formin activities; however, particular reaction rates vary significantly. Cdc12 is an efficient nucleator (one filament per approximately 3 Cdc12 dimers) that processively elongates profilin-actin at a moderate rate of 10 subunits s(-1) μM(-1), but lacks filament-bundling activity. Fus1 is also an efficient nucleator, yet processively elongates profilin-actin at one-half the rate of and dissociates 10-fold more rapidly than Cdc12; it also bundles filaments. For3 nucleates filaments 100-fold less well than Fus1, but like Cdc12, processively elongates profilin-actin at a moderate rate and lacks filament-bundling activity. Additionally, both the formin homology FH1 and FH2 domains contribute to the overall rate of profilin-actin elongation. We also confirmed the physiological importance of the actin-assembly activity of the fission yeast formins. Point mutants that disrupt their ability to stimulate actin assembly in vitro do not function properly in vivo.
authors.affiliation: Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA.
authors.forename: Bonnie J
authors.initials: BJ
authors.lastname: Scott
authors.forename: Erin M
authors.initials: EM
authors.lastname: Neidt
authors.forename: David R
authors.initials: DR
authors.lastname: Kovar
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D003599:Cytoskeleton / Q000235:genetics / Q000378:metabolism*; D000080865:Formins; D015966:Gene Expression Regulation, Fungal; D008856:Microscopy, Fluorescence; D009154:Mutation; D010957:Plasmids; D051304:Profilins / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012568:Schizosaccharomyces / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics*; D014161:Transduction, Genetic
chemical_list: D000199:Actins; C531994:Cdc12 protein, S pombe; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; C444419:FOR3 protein, S pombe; D000080865:Formins; D051304:Profilins; D029702:Schizosaccharomyces pombe Proteins; C490025:fus1 protein, S pombe