Figure 2From: Cytometry of chromatin bound Mcm6 and PCNA identifies two states in G1 that are separated functionally by the G1 restriction point1Stimulation of serum starved cells. BJ1 and RPE1 were serum starved for 24 h and then stimulated by addition of media with 10% serum. Samples were trypsinized, extracted with Triton X-100, fixed with MeOH, then stained and analyzed by flow cytometry. Data were preprocessed as in Additional file 3. Top panel:. the low Mcm6 G1 clusters (orange) decreased in frequency as a function of time, while the high Mcm6 (cyan) and PCNA positive S phase clusters (red-brown) increased. Lower panel: the fraction of cells residing in the low Mcm6 cluster (orange), high Mcm6 cluster, (cyan), and S phase (red-brown) were calculated as the percentage of G1 + S phase cells (Percent G1+S) and plotted as a function of time. The data were fit to constrained sigmoid equations with variable slopes (top = 100; bottom = 0). Kinetic analysis showed that the time to transit the high-Mcm6 state was 4.2 h for BJ1 and 2.1 h for RPE1 (arrows).Back to article page