Induction of GATA-binding in MDS and NBM. Cells were obtained and extracted at t = 0 (lanes 1, 8, 15), and after culture for 3 days with no factor (lanes 2, 9, 16) Epo (lanes 3, 10, 17), Epo + IL-3 (lanes 4, 11, 18) Epo + SCF (lanes 5, 12, 19), IL-3 (lanes 6, 13, 20), and SCF (lanes 7, 14, 21). Nuclear extracts of equivalent amounts of marrow cells from two MDS patients (no. 19, CMML; and no. 7, RAEB) and one NBM were incubated with the β-globin probe and run on a nondenaturing polyacrylamide gel. Position of the GATA-1–probe complex (as determined from co-runs with extracts from GATA-1–expressing cell lines) is indicated with an arrow. Lower bands are caused by binding of GATA-1 proteolytic fragments generated during culture and sample preparation. Lanes 15 through 21 are relatively overexposed as compared with lanes 1 through 14.