FIG. 5.

Activation of luciferase expression by DNA sequences 5′ of the FRNK unique leader exon. (A) pGL3 luciferase reporter constructs. A 2.4-kbp HindIII fragment (Hind8.3-1) which spans 1,989 bp upstream of the FRNK leader exon and includes 403 bp of the FRNK leader exon was cloned into the pGL3B vector in both correct (pH83C) and incorrect (pH83N) orientations. The pGL3C vector containing the SV40 promoter and enhancer was used as a positive control. (B) CEF were transfected with each of the pGL3 constructs depicted in panel A, and cell lysates were assayed for luciferase activity as described in Materials and Methods (10 μg of each construct was used per transfection unless otherwise indicated). β-Galactosidase activity of each lysate was measured, and luciferase activity for each lysate was normalized to the relative β-galactosidase activity of that lysate to give relative light units. Numbers denote fold activation over the pGL3B vector control. Error bars denote standard deviations from the means of three separate transfections. (C) SV40 enhancer-containing pGL3 luciferase reporter constructs. (D) CEF were transfected as for panel B with SV40 enhancer pGL3 constructs shown in panel C. Numbers denote fold activation over the pGL3E vector control. Error bars denote standard deviations from the means of three separate transfection events.