Background on Wnt signaling
Wnt signaling has essential functions in embryogenesis and tissue homeostasis, and its deregulation has been associated with oncogenesis. Activation of canonical Wnt pathway leads to the stabilization and accumulation of the transcriptional cofactor beta-catenin, which then activates the transcription of Wnt responsive genes. beta-catenin stability is normally regulated by phosphorylation at its N-terminal region, which targets beta-catenin for proteosomal degradation. Beta-catenin phosphorylation is mediated by a multiprotein complex, the destruction complex, consisting of two scaffold proteins, Axin and APC, and two Ser/Thr kinases, CKI and GSK-3beta. Wnt signal stabilizes beta-catenin by affecting the ability of the destruction complex to phosphorylate beta-catenin through an as yet unknown mechanism.