hTert-RPE1 cells exit the high-Mcm6 G1 state with similar kinetics as S phase cells. Exponentially growing RPE1 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. The three views shown are the same as in Figure 4. The top row shows the quantitative relationship between measured parameters for G1 and S cells. The middle row shows the decay of the high Mcm6 cluster and the decreasing intensity of the Mcm6 levels in the low Mcm compartment. The third view shows histograms of PCNA reactivity for G1 and S cells and 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.