MICROTUBULE TREADMILLING IN-VIVO

In vivo, cytoplasmic microtubules are nucleated and anchored by their minus ends at the centrosome and are believed to turn over by a mechan ism termed dynamic instability: depolymerization and repolymerization at their plus ends. In cytoplasmic fragments of fish melanophores, mic rotubules were shown to detach from their nucleation site and depolyme rize from their minus ends. Free microtubules moved toward the periphe ry by treadmilling-growth at one end and shortening from the opposite end. Frequent release from nucleation sites may be a general properly of centrosomes and permit a minus-end mechanism of microtubule turnove r and treadmilling.