K562-MERT cells arrest in the G₁/S phase of the cell cycle when Myb activity is inhibited. K562 (A-B) and K562-MERT (C-D) cells were cultured for 72 hours in the absence and presence of 1 μM tamoxifen. The DNA content in the PI-stained cells was measured by flow cytometry and analyzed by ModFitLT Mac V3 software. The first shaded peak is the G₀/G₁ phase and the second shaded peak is the G₂/M phase of the cell cycle. The hatched area between the 2 peaks is the S phase of the cell cycle. The insert contains the percentages of the total cell population in each phase of the cell cycle.