Figure 4
High CDK2 activity is required to initiate CDK4/6-independent cell cycle progression. (A‒D) Single-cell traces of CDK4/6 activity (left) and CDK2 activity (right) in wild type MCF-10A cells. Top to bottom, corresponding conditions under control (A), mitogen withdrawal (B), palbociclib (1 µM) (C), and 10 min NCS pulse (100 ng/ml) (D). All treatments performed 11 h after mitogen stimulation (marked in gray). Blue and red lines correspond to CDK2inc and CDK2low cells, respectively. Cells were classified based on CDK2 activity using 2 windows as indicated in (A). (E) Single-cell traces of CDK2 activity in p21/p27/p57 tKO MCF-10A cells. Control (left) and palbociclib (1 µM) (right) treatments were performed 11 h after mitogen stimulation (marked in gray). (F,G) Single-cell traces of CDK4/6 activity (left) and CDK2 activity (right) (F). Percentages of CDK2low cells increasing CDK2 activity at the time of inhibition (G). After 48 h mitogen removal, MCF-10A cells expressing DHFR-cyclin E1 were stimulated with mitogens together with DMSO or TMP (50 µM). Palbociclib (1 µM) treatment were performed 11 h after mitogen stimulation. Data are mean ± s.d. (n = 5 biological replicates) (G).
