Promoter-reporter activity of sequential 5′ deletion constructs. Promoter activity of all promoter constructs (diagrammed at left) was compared with that of pGL2:SV40 promoter with transient transfection of the constructs into H526, H146, HEL, and Jurkat cell lines. Cotransfection with pCMV βgal plasmid was used to control for transfection efficiency. After a 24-hour incubation, cell extracts were assayed, normalized for transfection efficiency, and relative reporter activity was determined. Error bars indicate standard error (SE) calculated from at least six separate electroporations. All activity values are relative to the pGL2:SV40 promoter, which was assigned a value of 1.0. Relative reporter gene activity was calculated as follows: luciferase activity divided by β-galactosidase activity, divided by the ratio obtained for the pGL2:SV40 promoter construct.