Role of the GC-rich and GATA elements in Dβ1 promoter activity. Luciferase reporter assays in p5424 cells in vectors containing Eβ. Promoters included full-length Dβ1 (+6Δ) and proximal (p150) or distal (d150) promoter fragments in wild-type form, with individual GC-rich mutations (m35, m281, m314), GATA site mutations (m74 or m276), Ikaros motif mutation (m255), or combinations of the GC-rich sites mutated as indicated by asterisks. The measured luciferase assay was corrected for transfection efficiency based upon Renilla luciferase controls. Average and standard error of 4 to 8 independent transfections for each construct is presented as a percentage of the luciferase activity obtained with the SV40 promoter/enhancer control vector.