The nuclear accumulation of wild-type and 5xE mutant of cyclin B1 in prophase is concurrent. (A) The nuclear accumulation of cyclin B1 in prophase was assayed in cells coexpressing wild-type (WT) cyclin B1–mCherry and 5xE cyclin B1–GFP. DIC (top), mCherry (middle), and GFP (bottom) images are shown. The region of interest used for quantification of the nuclear signal is displayed. Mean curves of quantifications in different cells are displayed (n = 6). Bar, 10 µm. (B) Cells were assayed as in A, and 300 nM Cdk inhibitor (Cdk1/2 inhibitor III) was added during prophase. Two examples are displayed. Error bars show SEM.