Loss of DOT1L inhibits cell proliferation because of a G₀/G₁ cell-cycle arrest. (A) In vitro TAM-induced DOT1L deletion inhibits proliferation of MLL-AF9–transformed cells in liquid culture but not MLL-AFX. Total cell numbers were counted every 2 days. Shown is the average of 3 independent experiments with error bars. (B) In vitro TAM-induced DOT1L deletion causes cell-cycle arrest at G₀/G₁ phase for MLL-AF9–transformed cells. Cell-cycle analysis was performed by PI staining. Experiment was repeated twice. Data were analyzed using ModFit software. (C) Gene-expression analysis by RT-qPCR shows up-regulation of CDK inhibitors after DOTL depletion, normalized to Gapdh.