The Golgi complex is a microtubule-organizing organelle

We show that the Golgi complex can directly stimulate microtubule nucleatio n in vivo and in vitro and thus behaves as a potent microtubule-organizing organelle in interphase cells. With the use of nocodazole wash-out experime nts in hepatic cells, we found that the occurrence of noncentrosomal, early stabilized microtubules is highly correlated with the subcellular localiza tion of Golgi membranes. With the use of in vitro reconstituted microtubule assembly systems with or without cytosol, we also found that, in contrast to centrosomally attached microtubules, the distal ends of Golgi-attached m icrotubules are remotely stabilized in a way that requires additional cytos olic component(s). Finally, we demonstrate that Golgi-based microtubule nuc leation is direct and involves a subset of gamma -tubulin bound to the cyto plasmic face of the organelle.