Plays a role in the organization of both preexisting and nascent microtubules in interphase cells. During mitosis, required for the organization and orientation of the mitotic spindle. Directly interacts with tubulin-gamma; this interaction determines centrosomal localization. Localized at the center of the radial microtubule array in interphase and at the spindle poles during various stages of mitosis. The coiled-coil domains may be important for tubulin-gamma-binding and hence for centrosomal localization.