The altered gene expression of G
phase cell cycle regulators at 6 h and changes in the distribution of cells within the cell cycle. A. A schematic of cell cycle regulation with proteins placed next to the phase of cell cycle with which they are associated (p19 and p21 are the products of the CDKN2D and CDKN1A genes, respectively). Gray, blue, and red indicate genes with unchanged, increased, or decreased expression, respectively, post toxin treatment. B. Cells in a subconfluent culture were treated with the indicated concentrations of toxin for 24 h. The DNA content of cells in each condition was quantified by PI fluorescence. The histograms of the area of PI fluorescence are normalized to the total number of cells (denoted as normalized cell count) in the sample such that the area under each histogram is equal to 1. In this way, the proportions of cells in each phase of the cell cycle may be compared for different size samples. The scale of the vertical axis is the same in each histogram. C. The percentage of cells in each phase of the cell cycle was calculated using ModFit LT software. Sub-G0/G1 cells were not included in the calculations.