Fig. 5.

EGR1 induction by ER stress is dependent on ELK1, but independent of SRF. (Panel A) HepG2 cells were transiently transfected with 100 nM siRNA against a non-targeting control (Ctrl) or Elk1 as described in the Methods section, and cultured for 48 h. Cells were incubated in DMEM ± Tg for 6 h and then steady state mRNA was measured by RT-qPCR for EGR1, GRP78, ELK1, and GAPDH as the internal control. (Panel B) HepG2 cells transfected with an siRNA against a non-targeting control (Ctrl) or Elk1 were cultured in DMEM ± Tg for 6 h. EGR1 protein was measured in whole cell extracts by immunoblotting. The protein level of β-actin was used as the control. (Panel C) HepG2 cells were transiently transfected with 100 nM siRNA against a non-targeting control (Ctrl) or SRF, as described in the Methods section, and cultured for 48 h. Cells were incubated in DMEM ± Tg for either 2 h or 6 h and then steady state mRNA for the indicated gene was measured by RT-qPCR. For Panels A and C, the target mRNA values were normalized to those for GAPDH within the same sample and the results shown are the means ± SD of triplicate samples within an experiment. The results shown are representative of multiple experiments. The data are graphed as relative values setting the DMEM value of either siControl, siELK1, or siSRF to 1.0. An asterisk indicates that the targeted siRNA value is significantly different (p ≤ 0.05) from the corresponding siControl.