LMP1 induces phosphorylation of eIF2α and expression of ATF4, which in turn leads to transactivation of LMP1's promoter dose-dependently. BJAB/HALMP1 cells were electroporated with an mRFP expression plasmid, a reporter plasmid that contains the CHOP promoter driving GFP gene expression, CHOP:GFP, and pgLRS (−106) CAT or pgLRS (−106)(ATF/CREmut.) CAT. pgLRS (−106) CAT has the wild-type ATF/CRE site, and pgLRS (−106)(ATF/CREmut.) CAT has a mutated ATF/CRE site in the −106 to +40 portion of the LMP1 promoter fused to chloramphenicol acetyl transferase (CAT). After 24 hours, electroporated cells were divided into 4 different plates and were either left untreated or treated with 300 pg/mL, 1 ng/mL, or 10/ng mL tetracycline for 48 hours to induce LMP1. (A) The cells were harvested and analyzed by Western blotting using antibodies to detect LMP1, phosphorylated eIF2α, total eIF2α, tubulin, ATF4, and GFP. 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) <.05 (Wilcoxon rank sum test).