Roles of β-catenin in the cell. β-catenin binds to E-cadherin and α-catenin at adherens junctions. In the vicinity of these juctions, α-catenin binds to actin as a homodimer. In the absence of Wnt signaling, β-catenin joins the destruction complex (green), where it is phosphorylated by CK1α and GSK-3β, which causes it to be ubiquitylated by the β-TrCP ubiquitin ligase and subsequently degraded by the proteasome. In the presence of a Wnt signal, β-catenin is not degraded and it moves to the nucleus, where it associates with DNA-binding members of the Tcf/LEF family and other associated transcription factors (not all of which are shown in the figure). This results in the activation of Wnt-target genes. Mutations in APC, axin or β-catenin lead to stabilization of β-catenin in the absence of a Wnt signal and consequent upregulation of Wnt-target genes.