Figure 6. Non-degradable cyclin A2 restores mitotic entry.

(a,b) HeLa cells stably expressing the indicated YFP-tagged Cdc20 proteins were synchronized as outlined in Fig. 3a and transfected with cyclin B1 L45A –CFP at 24 h before filming and monitored by time-lapse microscopy. Filming was started 2 h after release from the last thymidine block. Quantification of experiment shows percentage of cyclin B1 L45A–CFP-transfected cells, which enter mitosis during the course of the experiment. Mean of three experiments (at least 300 cells analysed in each condition) with error bars showing s.d. Representative still images from YFP–Cdc20^Ala is shown. Scale bar, 40 μm. (c,d) Quantification of live cell experiment similar to a,b. Percentage of cyclin A2 ΔN97–CFP-transfected cells, which enter mitosis during the course of the experiment compared with non-transfected cells. Mean of three independent experiments (at least 200 cells analysed in each condition) with error bars showing s.d. (e) The mean fluorescence intensity of cyclin B1 L45A–CFP and cyclin A2 ΔN97–CFP was analyzed in 20 cells from the experiments in a–d and plotted.