Cytokinesis requires the central spindle, which forms during anaphase by the bundling of antiparallel nonkinetochore microtubules. Microtubule bundling and completion of cytokinesis require MKLP1, a kinesin-6 family member, and RACGAP1 (MgcRacGap), which contains a RhoGAP domain. These form a heterotetrameric complex known as centralspindlin. Centralspindlin, but not its individual components, strongly promotes microtubule bundling in vitro.
