Loss of p21 does not protect FDM cells from cytokine deprivation, although loss of p53 delays cell-cycle exit. (A) FDM cells of the indicated genotype were deprived of IL-3 over a 48-hour time course. Lysates were prepared, and proteins were resolved on SDS-PAGE. Western blots were probed with antibodies to p21 and β-actin (loading control). (B) Cells of the indicated genotypes were deprived of IL-3 over a 24-hour time course. Cell-cycle distribution was analyzed by flow cytometric analysis. Representative FACS plots are shown for time 0 and 12 hours. (C) Cell-cycle distribution was analyzed for multiple independent clones (n) of the indicated genotypes as in panel B. The results shown are means ± SEMs of 4 independent experiments. (D) Multiple clones (n) of the indicated genotypes were cultured in the absence of IL-3 for 24 hours before cell viability was analyzed as described in Figure 1A. The results shown are means ± SEMs of 4 independent experiments.