Fig. 3. Role of different regions of the αENaC 3'UTR in the modulation of mRNA stability. Alveolar epithelial cells were transiently cotransfected with the pTRE-tight plasmid coding for V5-αENaC mRNA with the different αENaC 3'UTR deletion mutants along with pTet-Off plasmid that express tTA-Ad that allows the specific expression of the construct and its inhibition by doxycycline. Seventy-two h after transfection, cells were treated with doxycycline (1.0 ug/mL) from 15 min to 6 h. Expression of V5-αENaC mRNA was measured by quantitative RT-PCR and presented as percentage ± SEM of V5-αENaC mRNA expression of untreated cells (t=0) after normalization with tTA-Ad. V5-αENaC mRNA half-life for each construct was estimated by one-phase decay nonlinear regression. The V5-αENaC mRNA decay is shown for the clone with (A) complete 3'UTR (Comp) and (B-E) for the Del 1 to Del 4 3'UTR deletion mutants. (F) The half-life (t_1/2) of mRNA decay is given for each clone. In the lower right quadrant, the graph shows a comparison of the different t_1/2 ± SEM estimated for each clone. P<0.05 by Kruskal-Wallis tests between the different groups. * P<0.05 by Mann-Whitney U-tests compared to complete 3'UTR. ΦP<0.05 by Mann-Whitney U-tests compared to Del 1. Cells from at least five different animals (n≥5) were used for each experimental condition.