Kinesin-5 motors are required for organization of spindle microtubules in Silvetia compressa zygotes.
BACKGROUND
Monastrol, a chemical inhibitor specific to the Kinesin-5 family of motor proteins, was used to examine the functional roles of Kinesin-5 proteins during the first, asymmetric cell division cycle in the brown alga Silvetia compressa.


RESULTS
Monastrol treatment had no effect on developing zygotes prior to entry into mitosis. After mitosis entry, monastrol treatment led to formation of monasters and cell cycle arrest in a dose dependent fashion. These findings indicate that Kinesin-5 motors maintain spindle bipolarity, and are consistent with reports in animal cells. At low drug concentrations that permitted cell division, spindle position was highly displaced from normal, resulting in abnormal division planes. Strikingly, application of monastrol also led to formation of numerous cytasters throughout the cytoplasm and multipolar spindles, uncovering a novel effect of monastrol treatment not observed in animal cells.


CONCLUSIONS
We postulate that monastrol treatment causes spindle poles to break apart forming cytasters, some of which capture chromosomes and become supernumerary spindle poles. Thus, in addition to maintaining spindle bipolarity, Kinesin-5 members in S. compressa likely organize microtubules at spindle poles. To our knowledge, this is the first functional characterization of the Kinesin-5 family in stramenopiles.
Peters
Nick T
NT
Department of Biology, University of Utah, Salt Lake City, UT 84112, USA. npeters@biology.utah.edu
Kropf
Darryl L
DL
D016764:Cell Polarity / Q000187:drug effects; D003545:Cysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D048749:Cytokinesis / Q000187:drug effects; D004136:Dinitrobenzenes / Q000494:pharmacology; D016547:Kinesins / Q000378:metabolism*; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism*; D008938:Mitosis / Q000187:drug effects; D020409:Molecular Motor Proteins / Q000378:metabolism*; D017239:Paclitaxel / Q000494:pharmacology; D000459:Phaeophyceae / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011743:Pyrimidines / Q000494:pharmacology; D008941:Spindle Apparatus / Q000187:drug effects / Q000378:metabolism*; D013424:Sulfanilamides / Q000494:pharmacology; D013871:Thiones / Q000494:pharmacology; D015053:Zygote / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*
D004136:Dinitrobenzenes; D020409:Molecular Motor Proteins; D011743:Pyrimidines; D013424:Sulfanilamides; D013871:Thiones; C003724:3-tritylthio-L-alanine; C012465:oryzalin; C400223:monastrol; D016547:Kinesins; D003545:Cysteine; D017239:Paclitaxel