Organizing Microtubule Asters
Microtubules (MTs) are a critical component of the cytoskeleton, playing a role in a range of processes from cell polarization to division. MTs are polymers of αβ-tubulin that grow and shrink from a rapidly changing plus-end and a more slowly changing minus-end to form two primary architectures – linear bundles and radial asters. In most in vitrostudies, kinesin-14 family members have tended to form, slide, and sort MT bundles rather than assemble asters. These observations led Vanderbilt Basic Sciences investigator Marija Zanic and her collaborators Ryoma Ohi and Melanie Ohi (University of Michigan) to hypothesize that kinesin-14-dependent aster formation requires the presence of soluble tubulin dimers. They tested this hypothesis using the human kinesin-14 HSET expressed as a GFP conjugate. They showed that incubation of HSET-GFP with soluble tubulin and ATP/GTP resulted in aster formation.