title: Disruption of astral microtubule contact with the cell cortex activates a Bub1, Bub3, and Mad3-dependent checkpoint in fission yeast.
abstract: In animal and yeast cells, the mitotic spindle is aligned perpendicularly to the axis of cell division. This ensures that sister chromatids are separated to opposite sides of the cytokinetic actomyosin ring. In fission yeast, spindle rotation is dependent upon the interaction of astral microtubules with the cortical actin cytoskeleton. In this article, we show that addition of Latrunculin A, which prevents spindle rotation, delays the separation of sister chromatids and anaphase promoting complex-mediated destruction of spindle-associated Securin and Cyclin B. Moreover, we find that whereas sister kinetochore pairs normally congress to the spindle midzone before anaphase onset, this congression is disrupted when astral microtubule contact with the actin cytoskeleton is disturbed. By analyzing the timing of kinetochore separation, we find that this anaphase delay requires the Bub3, Mad3, and Bub1 but not the Mad1 or Mad2 spindle assembly checkpoint proteins. In agreement with this, we find that Bub1 remains associated with kinetochores when spindles are mispositioned. These data indicate that, in fission yeast, astral microtubule contact with the medial cell cortex is monitored by a subset of spindle assembly checkpoint proteins. We propose that this checkpoint ensures spindles are properly oriented before anaphase takes place.
authors.affiliation: Division of Yeast Genetics, National Institute for Medical Research, London NW7 1AA, United Kingdom.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Tournier
authors.forename: Yannick
authors.initials: Y
authors.lastname: Gachet
authors.forename: Vicky
authors.initials: V
authors.lastname: Buck
authors.forename: Jeremy S
authors.initials: JS
authors.lastname: Hyams
authors.forename: Jonathan B A
authors.initials: JB
authors.lastname: Millar
mesh_terms: D000705:Anaphase / Q000187:drug effects / Q000502:physiology; D064173:Anaphase-Promoting Complex-Cyclosome; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D018797:Cell Cycle Proteins / Q000032:analysis / Q000378:metabolism*; D002842:Chromatids / Q000378:metabolism; D019926:Cyclin B / Q000032:analysis / Q000378:metabolism; D005656:Fungal Proteins; D018386:Kinetochores / Q000276:immunology / Q000378:metabolism; D011494:Protein Kinases / Q000032:analysis / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D012568:Schizosaccharomyces / Q000378:metabolism* / Q000648:ultrastructure; D029702:Schizosaccharomyces pombe Proteins / Q000032:analysis / Q000378:metabolism*; D064249:Securin; D008941:Spindle Apparatus / Q000187:drug effects / Q000378:metabolism*; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D043743:Ubiquitin-Protein Ligase Complexes / Q000037:antagonists & inhibitors
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D018797:Cell Cycle Proteins; C103136:Cut2 protein, S pombe; D019926:Cyclin B; D005656:Fungal Proteins; D029702:Schizosaccharomyces pombe Proteins; D064249:Securin; D013844:Thiazoles; D053778:Thiazolidines; C512748:mad3 protein, S pombe; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D011494:Protein Kinases; C495594:Bub1 protein, S pombe; C090464:Bub1 spindle checkpoint protein; D017346:Protein Serine-Threonine Kinases; C037067:latrunculin A