Figure 1.

Activation of the iE_κ enhancer and enhancement of the iE_κ activity by LMP1 in human nasopharyngeal carcinoma cells. (A) Schematic diagram of human iE_κ-containing DNA fragment used in these experiments. Position of the iE_κ, the NF-κB and the AP-1 binding sites were shown. For simplicity, other protein-binding sites in the iE_κ were not shown. (B) Insertion sites for the definite DNA fragment into the pGL3-α plasmid which contains the human immunoglobulin Iα promoter and the firefly luciferase reporter gene. (C) Comparison of the activities of iE_κ in human nasopharyngeal carcinoma cell lines. Transient transfected the pα-iE_κwt construct, pGL3-α or pGL3-Basic vector into HNE2 and HNE2-LMP1 cells and luciferase reporter assays were performed as described in Materials and methods. The relative luciferase activity normalized to the value of the internal control plasmid pRL-SV40 activity. Results were expressed as fold induction of pGL3-Basic activity, which was assigned a value of 1. The data represent the mean ± SD of the three independent experiments performed in triplicate. Statistical significance: # P < 0.01 vs. pGL3-α-transfected HNE2, *P < 0.01 vs. pGL3-α-transfected HNE2-LMP1. (D) Transient expression of LMP1 increased the iE_κ activity in nasopharyngeal carcinoma cells. HNE2 cells were co-transfected with 400 ng/well of pα-iE_κwt, pGL3-α or pGL3-Basic vector and 80 ng/well of internal control pRL-SV40 together with 200 ng/well of pSG5-LMP1 or blank expression plasmid pSG5 (total DNA ~800 ng). Cells were harvested at 36 h after transfection and subjected to luciferase analysis. Statistical significance: # P < 0.01 vs. pSG5-transfected HNE2.