t-DARPP regulates β-catenin/TCF activation. β-catenin and TCF/LEF transcriptional activity was assessed using the luciferase reporter constructs, pTopFlash (with six TCF binding sites) and pFopFlash (with mutant binding site). AGS (A) MKN28 (B) and FLO-1 (C) cells that lack the expression of endogenous t-DARPP, were transiently transfected with different plasmid constructs as shown. The Western blot insets demonstrate the level of t-DARPP in representative transient transfection experiments. Overexpression of t-DARPP resulted in significant induction of β-catenin activity (p < 0.001) as indicated by an increase in luciferase activity of pTopFlash reporter. Co-transfection of t-DARPP pFopFlash reporter (mutant reporter) did not show any effect on luciferase activity. Results are representative of at least three experiments and shown as the mean with ± SD. Significance of difference was calculated using one-way ANOVA.