Figure 4.

PERK upregulates TAp73α expression through ATF4. (A-B) HCT116^p53-/- cells stably expressing shC or shATF4 were subjected to western blot analysis and qPCR analysis (B). (C-D) HCT116^p53-/- cells stably expressing empty vector (EV) or ATF4 were subjected to western blot analysis, in which cleaved-caspase 3 (C-caspase3) were be quantified based on total-caspase 3 (T-caspase3) or GAPDH (C) and qPCR analysis (D). ATF4 binding motifs was presented (top panel). The putative binding sites of ATF4 on TP73 promoter were predicted by JASPAR (bottom panel) and compared with the binding site of ATF4 on CHOP promoter (E). HCT116^p53-/- cells were treated by TM (2 μg/mL) for 24 h, then subjected to ChIP analysis. (G) HCT116^p53-/- cells stably expressing PERK were transduced with lentiviral vectors encoding shATF4 or shC, and then subjected to western blot analysis, in which cleaved-caspase 3 (C-caspase3) were be quantified based on total-caspase 3 (T-caspase3) or GAPDH. (H) HCT116^p53-/- cells stably expressing shATF4 or shC were treated with or without TM for 24 h and then subjected to western blot analysis, in which cleaved-caspase 3 (C-caspase3) were be quantified based on total-caspase 3 (T-caspase3) or GAPDH. The results are presented as the mean ± SD of three independent experiments; **P<0.01.