A MAP for Bundling Microtubules

Microtubules assemble into arrays of bundled filaments that are critical for multiple steps in cell division, including anaphase and cytokinesis. Recent structural and functional studies, including two papers in this issue of Cell ( Bieling et al., 2010 and Subramanian et al., 2010), demonstrate how the MAP65 protein PRC1 crosslinks microtubules and cooperates with kinesin motors to control the dynamics and size of bundled regions.