Fig. 3. NR controls β-catenin activity and the target gene expression of β-catenin. (A) 293T cells were co-transfected with β-catenin and USP4 to evaluate the effect of NR on β-catenin-mediated transcriptional (TOP flash) activity, and then NR was added at the indicated concentrations for 24 h. (B, C) HCT116 cells were exposed to NR (0 µM, 20 µM, and 40 µM) for 24 h with (B) or without (C) transfection of empty vector or SRT-USP4 plasmid. The mRNA expression of cyclin D1 and Axin2 (B), and β-catenin and USP4 (C) was quantified by real-time PCR and normalized to GAPDH. Error bars represent SD, **p< 0.01, ***p<0.001, ****p<0.0001.