FIG. 7.

The APC components Tsg24 and Cdc27 are bound to mitotic chromosomes. Protein extracts were prepared from mitotic CHO cells (m) and from isolated chromosomes prepared from mitotic CHO cells (pmc). The protein extracts were analyzed by immunoblotting with the anti-Tsg24, anti-P1, antipericentrin, anti-α-tubulin, and anti-Cdc27 antibodies. It is likely that the band with a unique molecular weight detected by the anti-Cdc27 antibody in extracts prepared from isolated mitotic cells is due to the artificial removal of posttranslational modifications (see the text) during the purification procedure, as this protein has been shown to be phosphorylated in mitotic cells (39).