Overview of the Wnt signaling pathway. (A) In the absence of a Wnt signal, β-catenin is captured within a destruction complex and phosphorylated. This results in ubiquitinylation and proteasomal degradation of β-catenin, ensuring repression of its target genes. (B) In the presence of a Wnt ligand, the destruction complex is inactivated and β-catenin translocates to the nucleus. In the nucleus, β-catenin becomes part of a transcriptionally active complex, ensuring efficient activation of its target genes. Professional illustration by Debra T. Dartez.