Regulation of filament dynamics during cell division

When cells divide, the mitotic spindle, a microtubule filament-based macromolecular machine segregates the chromosomes to the daugther cells. At the spindle poles, microtubule growth is initiated, but microtubules are also depolymerized to pull the microtubules and the attached chromosomes towards the poles. How these apparently antagonistic activities – polymerization and depolymerization are coordinated at the poles is not understood. By rebuilding the competition between microtubule nucleation and depolymerization using purified proteins in vitro and observing the dynamics of individual microtubules by fluorescence microscopy, we found out how three spindle pole-localized regulators with microtubule nucleating, cutting, and depolymerizing activities work together to generate the correct microtubule dynamics as observed in cells. This work explains mechanistically why a particular combination of microtubule regulating activities is combined at the spindle poles and how these activities ensure correct spindle dynamics at this position of thye spindle which is needed for correct cell division.