Figure 6.

Active cyclin A–Cdk2 complexes override the antephase checkpoint. DIC images of Ptk1 cells. Cells in early prophase were injected with cyclin A bound to either wild-type Cdk2 (top) or a Cdk2 T14A/Y15F mutant (bottom) that cannot be inactivated by phosphorylation. 5 min after injection, the cells were treated with 15 μM colcemid (0 min) and followed by time-lapse microscopy. Some cells arrested in prophase and were scored separately. Cells are representative of 9 mutant and 7 wild-type Cdk-injected cells in 14 independent experiments. Bar, 10 μm.