title: Dynein-mediated pulling forces drive rapid mitotic spindle elongation in Ustilago maydis.
abstract: Spindle elongation segregates chromosomes and occurs in anaphase, an essential step in mitosis. Dynein-mediated pulling forces position the spindle, but their role in anaphase is a matter of debate. Here, we demonstrate that dynein is responsible for rapid spindle elongation in the model fungus Ustilago maydis. We show that initial slow elongation is supported by kinesin-5, which is located in the spindle mid-zone. When the spindle reaches approximately 2 microm in length, the elongation rate increases four-fold. This coincides with the appearance of long and less-dynamic microtubules (MTs) at each pole that accumulate dynein at their tips. Laser-mediated nanosurgery revealed that these MTs exert pulling forces in control cells, but not in dynein mutants. In addition, dynein mutants undergo initial slow anaphase, but fail to establish less-dynamic MTs and do not perform rapid spindle elongation, suggesting that dynein drives anaphase B. This is most likely mediated by cortical sliding of astral MTs along stationary dynein, which is off-loaded from the MT plus-end to the cortex.
authors.affiliation: Max-Planck-Institut für Terrestrische Mikrobiologie, Marburg, Germany.
authors.forename: Gero
authors.initials: G
authors.lastname: Fink
authors.forename: Isabel
authors.initials: I
authors.lastname: Schuchardt
authors.forename: Julien
authors.initials: J
authors.lastname: Colombelli
authors.forename: Ernst
authors.initials: E
authors.lastname: Stelzer
authors.forename: Gero
authors.initials: G
authors.lastname: Steinberg
mesh_terms: D000705:Anaphase / Q000235:genetics; D004398:Dyneins / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D016547:Kinesins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D008941:Spindle Apparatus / Q000235:genetics / Q000378:metabolism*; D014588:Ustilago / Q000166:cytology / Q000235:genetics / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D004398:Dyneins; D016547:Kinesins