EXPERIMENTAL FIGURE 18-39 Microtubule dynamics increase in mitosis due to loss of a stabilizing MAP. (a) These three panels reveal the ability of centrosomes to assemble microtubules under various conditions: with pure tubulin (left); with tubulin and the destabilizing protein kinesin-13 (middle); and with tubulin, kinesin-13, and the stabilizing protein XMAP215 (Xenopus MAP of 215 kDa) (right). Further analysis shows that the major effect of XMAP215 is to suppress catastrophes induced by kinesin-13. (b) The increased dynamics of microtubules in mitosis is due to the inactivation of XMAP215 by phosphorylation. (c) Diagram comparing the stabilities of microtubules in interphase and in mitosis. Note that in addition to the decrease in stability in mitosis, the ability of MTOCs to nucleate microtubules increases dramatically in mitosis.

[Part (a) republished with permission of AAAS, from Kinoshita et al., “Reconstitution of Physiological Microtubule Dynamics Using Purified Components,” Science 294, no 5545,1340-1343 (2001). Part (b) data from Kinoshita et al, 2002, Trends Cell Biol. 12:267–273.]