Our research is concerned with the mechanism and regulation of microtubule polymerization and dynamics. Microtubules, major structural components of the cytoskeleton, are critical in cell shape and many types of cell movement. They are composed of the protein tubulin and have associated with their surfaces and ends a wide variety of proteins that regulate polymerization dynamics and function. Energy is released by the hydrolysis of GTP to GDP when tubulin adds to microtubule ends, that gives rise to growing and shortening transitions at the ends (called dynamic instability) and opposite end assembly and disassembly (treadmilling). Our work is aimed at understanding the mechanism and the regulation of these dynamic behaviors in relation to (a) mitosis in cancer cells and the mechanisms of action of microtubule-targeted anticancer drugs, and (b) the mechanisms of actions of microtubule regulatory proteins in neuronal cells such as the tau proteins and microtubule plus-tip tracking proteins.