Hela cells were synchronized in mitosis, released for various lengths of time, and collected at each mitotic phase: inter- (interphase), pro- (prophase), meta- (metaphase), ana-(anaphase), telo- (telophase), and cytokinesis. Endogenous p190 and ECT2 were immunostained with mouse anti-p190 and rabbit-ECT2 antibody, respectively, and analyzed by immunofluorescence microscopy as described in Methods. Co-localization of p190 and ECT2 was observed in the cleavage furrow.