Northern blot analysis of γ1 heavy Ig chain, GATA-1, and β globin gene expression in an Epo-R/TEPC clone. Epo-R/TEPC cells (clone E4), which were growth factor deprived for 18 hours, were stimulated with either IL-6 or Epo for different times ranging from 1 or 8 hours to 21 days. Total RNA was extracted and subjected to Northern blotting. (A) Analysis of γ1 Ig heavy chain expression. A 1.2-kb mRNA was detected after 18 hours (H0) of growth factor starvation and from 8 hours (H8) to 21 days (D21) after Epo (lanes 1) or IL-6 (lanes 2) stimulation. Hybridation of the same filter with an actin probe quantifies the amount of RNA loaded. (B) Analysis of GATA-1 gene expression. A mRNA of 1.8 kb was detected in MEL cells (lane C). No transcript was detected in Epo-R/TEPC cells from 1 hour (H1) to 21 days (D21) after Epo (lanes 1) or IL-6 (lanes 2) stimulation. 28 S RNAs are shown to evaluate the amount of RNA loaded. (C) Analysis of β globin gene expression. A 0.6-kb transcript was detected in bone marrow cells (lanes BMC). No globin mRNA was detected in Epo-R/TEPC cells from day 8 (D8) to day 21 (D21) after Epo (lanes 1) or IL-6 (lanes 2) stimulation. 28 S RNAs are shown to evaluate the amount of RNA loaded.