Activation of the human δ-globin gene promoter by restoring the CCAAT box. CCAAC site mutations (mtCCAAT and mt CCAAG) within the δ (−612 to +68)LUC plasmid were made by 2-step PCR site-directed mutagenesis. Transient transfection assays were performed in K562, MEL, and HeLa cell lines. LUC activity is relative to that of the SV40 promoter. The β promoter LUC plasmid used here spans sequences from −640 to +50 bp. Results are the mean ± SD of 3 independent experiments. *Difference (P < .05) from the wild-type (CCAAC) δ plasmid. (Because there is no or extremely low-level expression of β-globin gene in K562 cells,20 transfection of the βmtCCAAC plasmid was not performed).