EB1, a protein which interacts with the APC tumour suppressor, is associated with the microtubule cytoskeleton throughout the cell cycle

The characteristics of the adenomatous polyposis coli (APC) associated prot ein EB1 were examined in mammalian cells. By immunocytochemistry EB1 was sh own to be closely associated with the microtubule cytoskeleton throughout t he cell cycle, In interphase cells EB1 was associated with microtubules alo ng their full length but was often particularly concentrated at their tips, During early mitosis, EB1 was localized to separating centrosomes and asso ciated microtubules, while at metaphase it was associated with the spindle poles and associated microtubules. During cytokinesis EB1 was strongly asso ciated with the midbody microtubules, Treatment with nocodazole caused a di ffuse redistribution of EB1 immunoreactivity, whereas treatment with cytoch alasin D had no effect. Interestingly, treatment with taxol abolished the E B1 association with microtubules, In nocodazole washout experiments EB1 rap idly became associated with the centrosome and repolymerizing microtubules. In taxol wash-out experiments EB1 rapidly re-associated with the microtubu le cytoskeleton, resembling untreated control cells within 10 min, Immunost aining of SW480 cells, which contain truncated APC incapable of interaction with EEL, showed that the association of EB1 with microtubules throughout the cell cycle was not dependent upon an interaction with APC. These result s suggest a role for EB1 in the control of microtubule dynamics in mammalia n cells.