title: The role of actin in spindle orientation changes during the Saccharomyces cerevisiae cell cycle.
abstract: In the budding yeast Saccharomyces cerevisiae, the mitotic spindle must align along the mother-bud axis to accurately partition the sister chromatids into daughter cells. Previous studies showed that spindle orientation required both astral microtubules and the actin cytoskeleton. We now report that maintenance of correct spindle orientation does not depend on F-actin during G2/M phase of the cell cycle. Depolymerization of F-actin using Latrunculin-A did not perturb spindle orientation after this stage. Even an early step in spindle orientation, the migration of the spindle pole body (SPB), became actin-independent if it was delayed until late in the cell cycle. Early in the cell cycle, both SPB migration and spindle orientation were very sensitive to perturbation of F-actin. Selective disruption of actin cables using a conditional tropomyosin double-mutant also led to defects in spindle orientation, even though cortical actin patches were still polarized. This suggests that actin cables are important for either guiding astral microtubules into the bud or anchoring them in the bud. In addition, F-actin was required early in the cell cycle for the development of the actin-independent spindle orientation capability later in the cell cycle. Finally, neither SPB migration nor the switch from actin-dependent to actin-independent spindle behavior required B-type cyclins.
authors.affiliation: Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: C L
authors.initials: CL
authors.lastname: Theesfeld
authors.forename: J E
authors.initials: JE
authors.lastname: Irazoqui
authors.forename: K
authors.initials: K
authors.lastname: Bloom
authors.forename: D J
authors.initials: DJ
authors.lastname: Lew
mesh_terms: D000199:Actins / Q000378:metabolism*; D000705:Anaphase / Q000187:drug effects; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D017489:CDC28 Protein Kinase, S cerevisiae / Q000235:genetics / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000502:physiology; D002453:Cell Cycle / Q000187:drug effects; D018797:Cell Cycle Proteins / Q000235:genetics / Q000502:physiology; D016764:Cell Polarity / Q000187:drug effects; D019926:Cyclin B / Q000235:genetics / Q000502:physiology; D004398:Dyneins / Q000235:genetics / Q000502:physiology; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology; D005800:Genes, Fungal / Q000235:genetics / Q000502:physiology; D006918:Hydroxyurea / Q000494:pharmacology; D008840:Microfilament Proteins; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D009154:Mutation; D015739:Nocodazole / Q000494:pharmacology; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D008941:Spindle Apparatus / Q000187:drug effects / Q000378:metabolism*; D013696:Temperature; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D014335:Tropomyosin / Q000235:genetics / Q000378:metabolism
chemical_list: D000199:Actins; C105191:Bni1 protein, S cerevisiae; D019086:Bridged Bicyclo Compounds, Heterocyclic; C083769:CDC31 protein, S cerevisiae; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D019926:Cyclin B; D005656:Fungal Proteins; C110443:KAR9 protein, S cerevisiae; D008840:Microfilament Proteins; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; D013844:Thiazoles; D053778:Thiazolidines; D014335:Tropomyosin; D017489:CDC28 Protein Kinase, S cerevisiae; D004398:Dyneins; D015739:Nocodazole; C037067:latrunculin A; D006918:Hydroxyurea