FIG. 3.

GATA-1 expression in FDCW2ER-pMG1 cells prolongs the G₁ phase of the cell cycle during Epo-stimulated mitogenesis. (A) Epo- versus IL-3-stimulated cell cycle progression in FDCW2ER-pMG1 and control FDCW2ER cells. FDCW2ER-pMG1 and FDCW2ER cells were washed free of cytokines and were cultured for 7.5 h in Opti-MEM I medium containing 1.5% FBS to promote synchrony. The cells then were exposed to either Epo or IL-3, and cell cycle distributions were analyzed at 4-h intervals by propidium iodide staining and flow cytometry. (B) GATA-1 transcript expression in FDCW2ER-pMG1 and FDCW2ER-pCG1 cells. To confirm exogenous GATA-1 expression, total RNA from FDCW2ER-pCG1 and FDCW2ER-pMG1 cells (and from FDCW2, FDCW2ER, and erythroid SKT6 cells as controls) was isolated and levels of GATA-1 and Epo receptor transcripts were assayed by Northern blotting. An additional control cell line, FDCW2ER-pCEKLF, also was analyzed for Epo receptor, EKLF, and GATA-1 transcript expression. Hybridizations were performed sequentially by using a single blot, and equivalence in loading was confirmed by hybridization to a GAPDH probe.