Only the 6 transmembrane domains of LMP1 are necessary for induction of ATF4's expression and transactivation of LMP1's promoter. BJAB/HA6MLMP1-GFP cells were electroporated with mRFP, CHOP:GFP, and pgLRS (−106) and then divided into 4 different plates. After 24 hours, cells were either left untreated or treated with 30 pg/mL, 300 pg/mL, or 10 ng/mL tetracycline for 48 hours to induce LMP1. The cells were harvested and analyzed by Western blotting (A) using antibodies to detect LMP1, phosphorylated eIF2α, total eIF2α, tubulin, GFP, and ATF4. A representative gel of 3 independent experiments is shown. (B) The cells were harvested and analyzed by CAT assays. The activity is given as the fold-difference relative to the activity of pgLRS (−106) CAT in the absence of tetracycline, which was set at 1. Averages and standard deviations of 3 independent experiments are shown. **P (2-sided) <.01 (Wilcoxon rank sum test).