Dengue infection induces the upregulation of GADD34 mRNA. (A) A549 cells were either treated with increasing concentration of thapsigargin (TG) for 1 hour or infected with DENV2 or DENV1 viruses (10 MOI) at indicated time points. GADD34 mRNA (top panel) and β-actin mRNA (bottom panel) levels were determined by semi-quantitative RT-PCR with specific primers (see Materials and Methods). (B) Densitometric quantification of GADD34 mRNA levels from (A) were normalized to β-actin mRNA levels and plotted in histograms (TG) or graphs (DEN1 and 2). The ratio of the GADD34 to β-actin of the uninfected (Mock) sample was considered as basal level (0 hour) and negative value was also represented as basel level. (C) A549 cells were infected with either 1 moi of DENV1 (MY10245) or DENV2 (TSV01). Virus production after Day 1, Day 2 and Day 3 of infection were quantified by plaque assay and expressed by PFU/ml.