Northern blot analysis of wild type and mutant C/EBPɛ induction in 32Dcl3/tet cells. (A) Three clones of 32D/tetC/EBPɛ wild-type A, E, and F were grown both in the presence (+, lanes 1, 3, and 5) and absence (−, lanes 2, 4, and 6) of tetracycline for 4 days. Total RNA was extracted from each set of cells and 10 μg was subjected to Northern blot analysis. The blot was sequentially probed with 32P-labeled cDNA for C/EBPɛ, mouse lactoferrin (LF), and β-actin. (B) A similar Northern blot was carried out for the 32Dcl3/tet cells transfected with the pUHD10-3 vector alone. (C) Two clones, MutA and MutB, of 32D/tetC/EBPɛ harboring a mutant C/EBPɛ lacking the basic region/leucine zipper (bZip) domain (SGD mutation) were grown both in the presence (+, lanes 1, 3, and 5) and absence (−, lanes 2, 4, and 6) of tetracycline for 4 days. Total RNA was extracted from each set of cells and subjected to Northern blot analysis. The blot was sequentially probed with 32P-labeled cDNA for C/EBPɛ, mouse lactoferrin (LF), and β-actin.