Regulation of microtubule dynamic instability.

Characterization of microtubule assembly in vivo and in vitro has raised questions of how cells regulate dynamic instability. While dynamic instability is an intrinsic property of the tubulin molecule, factors are required to increase the plus-end elongation rate and increase the frequencies of both catastrophe and rescue to achieve cellular tubulin turnover rates. It is likely that the activities of the transition frequency regulators are themselves regulated during the cell cycle, but the mechanisms of regulation are not known. As we identify the proteins which alter microtubule assembly, new classes of MAPs will emerge. An understanding of how these proteins function may provide further insight into how cells organize the different arrays of microtubules used for such processes as vesicle transport, polarized organization of organelles, and chromosome movement.