Functional activity of pXP2-MBP (P2) luciferase constructs in the eosinophilic HL-60-C15 cell line. Promoter activities of additional 5′ deletion mutants of the MBP-pXP2 construct in HL-60-C15 cells. Fifteen micrograms of each MBP-pXP2 construct was transfected along with 10 μg of pBluescript II KS(−) as carrier DNA. Luciferase activities have been normalized for the amount of hGH produced by cotransfection with a control CMV-hGH expression vector. Corrected RLU for each construct are shown as the percent activity relative to the mean activity of the longest 3.2-kb MBP (P2) promoter construct. The mean ± SEM for three replicate experiments is shown.