Characterization of NIH 3T3 cells carrying zinc-inducible CEBPA, CEBPB, CEBPD, or CEBPE genes. (A) NIH 3T3 cell lines stably transfected with zinc-inducible cDNA coding for C/EBP proteins (pMTα, pMTβ, pMTδ, and pMTϵ) and cells transfected with empty vector (pMT) were treated with zinc for 16 hours. Protein lysates were analyzed by Western blot with C/EBPα-, C/EBPβ-, C/EBPδ-, or C/EBPϵ-specific antibodies. The blots were stripped and rehybridized with a GAPDH antibody as control for equal loading. (B) Semiquantitative RT-PCR was performed on RNAfrom the NIH 3T3 cell lines incubated with zinc for 16 hours. PCR products of haptoglobin (Hp, 25 and 33 cycles) and lipocalin (Lcn2, 33 cycles) were gel separated and stained with ethidium bromide. PCR for 18S was carried out as an internal control.