β-catenins are cytoplasmic proteins that are ubiquitously expressed. These proteins associate with E-cadherin at cellular junctions. CTNNB1 (catenin β-1) belongs to the armadillo family of proteins. This protein possesses a 130 amino acid N-terminal domain, 12 imperfect repeats of 42 amino acids termed arm repeats and a 100 amino acid C-terminal domain. The gene encoding β-catenin is localized on human chromosome 3p22.1.
β-catenin interacts with T-cell factor and lymphoid enhancer-binding factor (TCF and LEF) transcription factors and is an essential member of the Wingless-Wnt signal transduction pathway. The adenomatous polyposis coli (APC) tumor-suppressor protein, together with Axin and glycogen synthase kinase 3 β (GSK3β), form a Wnt-regulated signaling complex that mediates phosphorylation-dependent degradation of βcatenin by the proteasome. APC and the Siah-1 E3 ubiquitin-protein ligase-1 mediate a novel β-catenin degradation pathway linking p53 activation to cell cycle control. Activating mutations in the human β-catenin gene have been found in human colon cancer and melanomas. The protein has a role in homeostasis and development.
