The centromere protein CENP-B behaves as a microtubule-associated protein

The centromere of mitotic chromosomes organizes the kinetochore, a proteinaceous matrix that interfaces with spindle microtubules at one plane and with the centromeric DNA at the other. Antibodies present in the sera from patients with CREST scleroderma recognize several proteins localized to the centromere. We have studied the ability of the two main human centromere proteins CENP-A (18 kD) and CENP-B (80 kD) to bind tubulin, in order to correlate with one of the putative functional roles in spindle microtubule attachment. CENP-A was partially solubilized from nuclear extracts by high salt treatment and then purified by reverse phase HPLC. CENP-B was obtained by gel electrophoresis and electroelution from nuclear insoluble extracts. CENP-B binds to tubulin while no significant interaction was found for CENP-A. CENP-B binds to the C-terminal region of tubulin, a characteristic similar to that found for other better characterized microtubule-associated proteins.