Figure 1.

TPA induces luciferase reporter activity independent of the distance between HS2 and the promoter. K562 clonal cell lines, stably transfected with either of the constructs shown, were treated with TPA for 20 h, and then luciferase activity was determined from cell lysates as a measure of γ-globin promoter activity (mean ± SEM). At least triplicate measurements were made for each TPA concentration. The copy number of integrated templates was 8, 2, 22, and 1 for clones HS2(2.2)-1, HS2(2.2)-2, HS2(7.3)-1, and HS2(7.3)-2, respectively.