title: Microtubule interactions with the cell cortex causing nuclear movements in Saccharomyces cerevisiae.
abstract: During mitosis in budding yeast the nucleus first moves to the mother-bud neck and then into the neck. Both movements depend on interactions of cytoplasmic microtubules with the cortex. We investigated the mechanism of these movements in living cells using video analysis of GFP-labeled microtubules in wild-type cells and in EB1 and Arp1 mutants, which are defective in the first and second steps, respectively. We found that nuclear movement to the neck is largely mediated by the capture of microtubule ends at one cortical region at the incipient bud site or bud tip, followed by microtubule depolymerization. Efficient microtubule interactions with the capture site require that microtubules be sufficiently long and dynamic to probe the cortex. In contrast, spindle movement into the neck is mediated by microtubule sliding along the bud cortex, which requires dynein and dynactin. Free microtubules can also slide along the cortex of both bud and mother. Capture/shrinkage of microtubule ends also contributes to nuclear movement into the neck and can serve as a backup mechanism to move the nucleus into the neck when microtubule sliding is impaired. Conversely, microtubule sliding can move the nucleus into the neck even when capture/shrinkage is impaired.
authors.affiliation: Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: N R
authors.initials: NR
authors.lastname: Adames
authors.forename: J A
authors.initials: JA
authors.lastname: Cooper
mesh_terms: D000199:Actins / Q000235:genetics; D002467:Cell Nucleus / Q000502:physiology*; D003598:Cytoskeletal Proteins; D000072159:Dynactin Complex; D004398:Dyneins / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics; D017353:Gene Deletion; D005800:Genes, Fungal; D018715:Microscopy, Video; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000502:physiology*; D008938:Mitosis / Q000502:physiology*; D008954:Models, Biological; D009068:Movement / Q000502:physiology*; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000166:cytology*; D029701:Saccharomyces cerevisiae Proteins; D008941:Spindle Apparatus / Q000378:metabolism
chemical_list: C089021:ARP1 protein, S cerevisiae; D000199:Actins; D003598:Cytoskeletal Proteins; D000072159:Dynactin Complex; C405804:EB1 microtubule binding proteins; D005656:Fungal Proteins; D008869:Microtubule-Associated Proteins; D029701:Saccharomyces cerevisiae Proteins; D004398:Dyneins