FIG. 5.

Attenuation of Epo- and IL-3-dependent proliferation and cell cycle progression in FDCW2ER-pXG1 cells. (A) Effects of GATA-1 expression on Epo- and IL-3-dependent proliferation in FDCW2ER-pXG1 cells. Cytokine-induced growth of FDCW2ER-pXG1 and control FDCW2ER cells was assayed by scoring cell numbers (mean and standard deviation) every 24 h over a 72-h period (top). Also assayed were rates of Epo- and IL-3-induced incorporation of [methyl-³H]thymidine (mean and standard deviation) (bottom). The results shown for growth and [methyl-³H]thymidine incorporation are representative of three independent experiments. (B) GATA-1 expression results in an Epo-specific prolongation of the G₁ phase in FDCW2ER-pXG1 cells. FDCW2ER-pXG1 and control FDCWER cells were washed free of cytokines and incubated for 7.5 h in Opti-MEM I medium–1.5% FBS to promote synchrony. Following stimulation with Epo, the cells were stained with propidium iodide and the cell cycle distributions were determined.