Time course of induction of immediate-early gene expression after Epo or IL-6 stimulation of Epo-R/TEPC clones. Epo-R/TEPC cells were washed, grown in the absence of growth factors for 18 hours, and then stimulated with IL-6 or Epo for 20 minutes to 4 hours. Total RNA was extracted and electrophoresed on a 1% agarose gel. (A) c-myc induction. A c-myc probe detects normal (2.4 kb) and abnormal (4.0 kb) transcripts. (B) JunB and c-fos induction. A junB probe detects a 1.8-kb transcript. A c-fos probe detects a 2.2-kb transcript. Lanes 1, before stimulation; lanes 2, 20 minutes; lanes 3, 1 hour; lanes 4, 3 hours; lanes 5, 4 hours of Epo or IL-6 stimulation. NIH/3T3 fibroblasts were used as control for the expression of c-fos and JunB. These fibroblasts were deprived of FCS (lanes 1) and stimulated by FCS for 20 minutes (lanes 2), 1 hour (lanes 3), and 3 hours (lanes 4).