title: Localization and function of Kinesin-5-like proteins during assembly and maintenance of mitotic spindles in Silvetia compressa.
abstract: BACKGROUND
  Kinesin-5 (Eg-5) motor proteins are essential for maintenance of spindle bipolarity in animals. The roles of Kinesin-5 proteins in other systems, such as Arabidopsis, Dictyostelium, and sea urchin are more varied. We are studying Kinesin-5-like proteins during early development in the brown alga Silvetia compressa. Previously, this motor was shown to be needed to assemble a bipolar spindle, similar to animals. This report builds on those findings by investigating the localization of the motor and probing its function in spindle maintenance.
  
  
  RESULTS
  Anti-Eg5 antibodies were used to investigate localization of Kinesin-5-like proteins in brown algal zygotes. In interphase zygotes, localization was predominantly within the nucleus. As zygotes entered mitosis, these motor proteins strongly associated with spindle poles and, to a lesser degree, with the polar microtubule arrays and the spindle midzone. In order to address whether Kinesin-5-like proteins are required to maintain spindle bipolarity, we applied monastrol to synchronized zygotes containing bipolar spindles. Monastrol is a cell-permeable chemical inhibitor of the Kinesin-5 class of molecular motors. We found that inhibition of motor function in pre-formed spindles induced the formation of multipolar spindles and short bipolar spindles.
  
  
  CONCLUSIONS
  Based upon these localization and inhibitor studies, we conclude that Kinesin-5-like motors in brown algae are more similar to the motors of animals than those of plants or protists. However, Kinesin-5-like proteins in S. compressa serve novel roles in spindle formation and maintenance not observed in animals.
authors.affiliation: Biology Department, University of Utah, Salt Lake City, Utah, USA. npeters@biology.utah.edu
authors.forename: Nick T
authors.initials: NT
authors.lastname: Peters
authors.forename: Anne Catherine
authors.initials: AC
authors.lastname: Miller
authors.forename: Darryl L
authors.initials: DL
authors.lastname: Kropf