title: Subunit-dependent modulation of septin assembly: budding yeast septin Shs1 promotes ring and gauze formation.
abstract: Septins are conserved guanosine triphosphate-binding cytoskeletal proteins involved in membrane remodeling. In budding yeast, five mitotic septins (Cdc3, Cdc10, Cdc11, Cdc12, and Shs1), which are essential for cytokinesis, transition during bud growth from a patch to a collar, which splits into two rings in cytokinesis and is disassembled before the next cell cycle. Cdc3, Cdc10, Cdc11, and Cdc12 form an apolar octameric rod with Cdc11 at each tip, which polymerizes into straight paired filaments. We show that Shs1 substitutes for Cdc11, resulting in octameric rods that do not polymerize into filaments but associate laterally, forming curved bundles that close into rings. In vivo, half of shs1Δ mutant cells exhibit incomplete collars and disrupted neck filaments. Importantly, different phosphomimetic mutations in Shs1 can either prevent ring formation or promote formation of a gauzelike meshwork. These results show that a single alternative terminal subunit is sufficient to confer a distinctive higher-order septin ultrastructure that can be further regulated by phosphorylation.
authors.affiliation: Division of Biochemistry and Molecular Biology, Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA.
authors.forename: Galo
authors.initials: G
authors.lastname: Garcia
authors.forename: Aurelie
authors.initials: A
authors.lastname: Bertin
authors.forename: Zhu
authors.initials: Z
authors.lastname: Li
authors.forename: Yi
authors.initials: Y
authors.lastname: Song
authors.forename: Michael A
authors.initials: MA
authors.lastname: McMurray
authors.forename: Jeremy
authors.initials: J
authors.lastname: Thorner
authors.forename: Eva
authors.initials: E
authors.lastname: Nogales
mesh_terms: D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C099502:CDC11 protein, S cerevisiae; D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; C115656:SHS1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins