Fig. 5.

MiR-431 reduces SMAD4 expression by targeting the SMAD4 3′-UTR in A549 cells. a – TargetScan showing the subcloning of the predicted miR-431-binding site at position 1121–1127 of the SMAD4 3′-UTR into a luciferase construct. b – Luciferase reporter gene assay verification of the bioinformatics analysis. SMAD4 was predicted as a target gene of miR-431 (n = 3). c – The mRNA expression of SMAD4 in A549 cells transfected with miR-431-5p mimic, mimic nc, inhibitor or inhibitor nc. d – Western blotting of SMAD4 in A549 cells transfected with miR-431-5p mimic, mimic nc, inhibitor or inhibitor nc. e – The protein expression of SMAD4 in A549 cells transfected with miR-431-5p mimic, mimic nc, inhibitor or inhibitor nc (n = 3). *p < 0.05; **p < 0.01; ***p < 0.001 vs. miR-431-5p negative control