Figure 4

hTert-BJ1 cells exit the high-Mcm6 G1 state with similar kinetics as S phase cells. Exponentially growing BJ1 cells were switched to media containing 0.03% serum. At the indicated times, cells were harvested with trypsin and extracted with Triton X-100 prior to MeOH fixation, then stained, and subjected to cytometry. The regions for quantifying the fractions of cells in the three clusters were set as in Figure 2. Three views are shown. The first is a bivariate plot of G1 and S cells (top row). The second view, histograms of Mcm6 reactivity for G1 cells only, shows the decay of the high Mcm6 cluster and the decreasing intensity of the Mcm6 levels in the low Mcm compartment (middle row). The third view, histograms of PCNA reactivity for G1 and S cells, shows the decay of both the high Mcm6 cluster and the PCNA positive S phase cells (bottom row). Note: the Y axes in panels in the middle and bottom rows have variable scales.