FIGURE 2.

TDG activates Wnt signaling. A, TDG enhanced Wnt3A-induced TOPFlash reporter activity. TOPFlash or FOPFlash was cotransfected with Wnt3A and Renilla plasmids into HEK293T cells with or without TDG and Gadd45. Top panel, relative luciferase reporter activity adjusted with Renilla. *, p < 0.05. Bottom panel, expression levels of TDG and Gadd45. B, TDG enhanced β-catenin-induced TOPFlash reporter activity. TOPFlash or FOPFlash was cotransfected with β-catenin (β-cat) and Renilla plasmids into HEK293T cells with or without TDG and Gadd45. Top panel, relative luciferase reporter activity adjusted with Renilla. *, p < 0.05. Bottom panel, expression levels of β-catenin, TDG, and Gadd45. C, β-catenin binds TCF4 but does not bind TDG. FLAG-tagged TDG or TCF4 and HA-tagged β-catenin (S33A mutant) were transfected into HEK293T cells. TDG or TCF4 was immunoprecipitated (IP) with an anti-FLAG Ab, and β-catenin was analyzed by Western blot analysis with an anti-HA Ab. TDG, TCF4, and β-catenin in the cell lysates were analyzed by Western blot analysis. D, TDG binds TCF4. FLAG-tagged TDG and HA-tagged TCF4 were transfected into HEK293T cells. TDG was immunoprecipitated with an anti-FLAG Ab, and TCF4 was analyzed by Western blot analysis with an anti-HA Ab. TDG and TCF4 in the cell lysates were analyzed by Western blot analysis. E, interaction between endogenous TDG and TCF4. Endogenous TDG was immunoprecipitated from HEK293T cells using an anti-TDG Ab. The presence of TCF4 was analyzed by Western blot analysis with an anti-TCF4 Ab. An unrelated Ab was used as a negative control for immunoprecipitation.