Dynein/dynactin regulate metaphase spindle length by targeting depolymerizing activities to spindle poles.
During cell division metaphase spindles maintain constant length, whereas spindle microtubules continuously flux polewards, requiring addition of tubulin subunits at microtubule plus-ends, polewards translocation of the microtubule lattice, and removal of tubulin subunits from microtubule minus-ends near spindle poles. How these processes are coordinated is unknown. Here, we show that dynein/dynactin, a multi-subunit microtubule minus-end-directed motor complex, and NuMA, a microtubule cross-linker, regulate spindle length. Fluorescent speckle microscopy reveals that dynactin or NuMA inhibition suppresses microtubule disassembly at spindle poles without affecting polewards microtubule sliding. The observed uncoupling of these two components of flux indicates that microtubule depolymerization is not required for the microtubule transport associated with polewards flux. Inhibition of Kif2a, a KinI kinesin known to depolymerize microtubules in vitro, results in increased spindle microtubule length. We find that dynein/dynactin contribute to the targeting of Kif2a to spindle poles, suggesting a model in which dynein/dynactin regulate spindle length and coordinate flux by maintaining microtubule depolymerizing activities at spindle poles.
Laboratory of Chemistry and Cell Biology, The Rockefeller University, 1230 York Ave., Box 202, New York, NY 10021, USA.
Jedidiah
J
Gaetz
Tarun M
TM
Kapoor
D000818:Animals; D018797:Cell Cycle Proteins; D018385:Centrosome / Q000648:ultrastructure; D003432:Cross-Linking Reagents / Q000494:pharmacology; D000072159:Dynactin Complex; D004398:Dyneins / Q000502:physiology*; D005982:Glutathione Transferase / Q000378:metabolism; D016547:Kinesins / Q000378:metabolism; D007700:Kinetics; D008677:Metaphase; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000378:metabolism / Q000502:physiology*; D008870:Microtubules / Q000378:metabolism / Q000648:ultrastructure; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins; D008941:Spindle Apparatus; D014404:Tubulin / Q000096:biosynthesis / Q000737:chemistry; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000378:metabolism
D018797:Cell Cycle Proteins; D003432:Cross-Linking Reagents; D000072159:Dynactin Complex; D008869:Microtubule-Associated Proteins; C489079:NUMA1 protein, Xenopus; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; C489080:Numa1 protein, mouse; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D014404:Tubulin; D029867:Xenopus Proteins; D005982:Glutathione Transferase; C477238:KIF2A protein, mouse; D004398:Dyneins; D016547:Kinesins