FIGURE 3.

Identification of GRP78/BIP promoter elements responsible for transcriptional down-regulation by E2F1. The 5′-deletion mutants of the human GRP78/BIP promoter cloned upstream of the firefly luciferase gene are shown by nucleotide positions. Locations of the GC-boxes, ER stress elements (1-3), and TATA-box are indicated. The transcription start site of the GRP78/BIP gene is indicated by an arrow. 0.5 μg of the indicated reporter constructs either alone or together with 0.5 μg of E2F1 expression plasmid were transfected into H1299 cells. Luciferase activity (RLU) was measured 36 h after transfection. Data were obtained from three replicates. Error bars, one S.D. Protein expression levels in E2F1-transfected cells are indicated (bottom panel). Actin was used for equal loading.