Wnt/beta-catenin signaling induces the expression and activity of beta TrCP ubiquitin ligase receptor

beta-transducing repeat-containing protein (beta TrCP) targets the ubiquiti nation and subsequent degradation of both beta-catenin and I kappa B, there by playing an important role in beta-catenin/Tcf and NF-kappa B-dependent s ignaling. Here evidence is presented that beta-catenin/Tcf signaling elevat es the expression of beta TrCP mRNA and protein in a Tcf-dependent manner, which does not require beta TrCP transcription. Induction of beta TrCP expr ession by the beta-catenin/Tcf pathway results in an accelerated degradatio n of the wild-type beta-catenin, suggesting that the negative feedback loop regulation may control the beta-catenin/Tcf pathway. This signaling also u pregulated NF-kappa B transactivation without affecting the activity of I k appa B kinase, thereby establishing that the maintenance of the beta TrCP l evel is important for coordination between beta-catenin/Tcf and NF-kappa B signaling.