(A) Effect of C/EBPɛ isoforms p32 and p30 and C/EBP on transcription of promoter-reporter plasmids for the mim-1, neutrophil elastase, and G-CSF receptor promoters in CV-1 cells. Maximal activation was achieved with 500 ng of the expression vector. C/EBPɛ p32 activated the promoters 2.5-, 1.8-, and 1.6-fold, respectively. C/EBPɛ p30 showed only a small effect on the mim-1 promoter (1.5-fold activation). C/EBP was used as a positive control and activated the reporters approximately twofold to fourfold. For experiments using the mim-1 and neutrophil elastase promoter constructs, transactivation by the empty expression plasmid served as the baseline. (B) Effect of C/EBPɛ isoforms p32 and p30 on transcriptional activation of mim-1 and neutrophil elastase promoter in T-cell leukemia cell line Jurkat. Isoform p32 is 3.5-fold more active than p30 on the mim-1 promoter and 1.5-fold more active on the neutrophil elastase promoter. (C) Western blot demonstrates that transfected Jurkat cells expressed equal amounts of C/EBPɛ p32 and p30. (D) Dose-response curve for transcriptional activation potential of C/EBPɛ p30, p32, and C/EBP on mim-1 promoter in T-cell leukemia cell line Jurkat.