Fig. 4.

The conserved DLLC peptide in the viral oncoproteins is essential for the PERK-mediated UPR. a–d HEK293T cells were transfected with PERK-Flag and the indicated viral oncogene plasmids, followed by stimulation with 1 mg/ml Tg for 1 h. PERK was immunoprecipitated, and the oligomerization of PERK was evaluated by negative gel electrophoresis. The quantification of the oligomerization of PERK was shown in the lower panel. e CNE1 cells were stably transfected with an empty vector (EV), LMP1^WT, or LMP1^4A, followed by immunoblotting to monitor PERK activity. f CNE1 cells stably expressing the EV, LMP1^WT or LMP1^4A were treated with 1 μM Tg at the indicated times. The PERK-mediated UPR was examined by immunoblotting. g C33A cells were stably transfected with the EV, E7^WT or E7^4A, followed by immunoblotting to monitor PERK activity. h C33A cells stably expressing the EV, E7^WT, or E7^4A were treated with 1 μM Tg at the indicated times. Then, the PERK-mediated UPR was examined by immunoblotting. All data are presented as the mean ± SEM of three independent experiments. The values of p < 0.05 were considered statistically significant. ns means no significant