Expression of reporter luciferase directed by portions of the bcl-x promoter in transient transfection assays.

Portions of the bcl-x promoter bearing the complete sequence from −1 (nucleotide preceding A of the ATG codon) to the indicated nucleotide on the horizontal axis were placed in the luciferase reporter vector pGL3 Basic Vector (Promega). The constructs were transfected into HCD57 cells, and the firefly luciferase was measured after 24 hours. A control expression plasmid, pRL-TK, was cotransfected, as described in “Materials and methods.” The ratio of firefly luciferase to Renilla luciferase was determined in the transfected cells. That ratio for the pGL3 luciferase vector without any inserted promoter sequence was adopted as the baseline expression value. Each transfection assay was performed 3 to 5 times, and representative values are shown. For all test plasmids, the range of values obtained in repetitive experiments was less than 15% of the values shown.