Recombinant Xenopus laevis Catenin beta (ctnnb1), partial

Key downstream component of the canonical Wnt signaling pathway. In the absence of Wnt, forms a complex with axin1, axin2, apc, csnk1a1 and gsk3b that promotes phosphorylation on N-terminal Ser and Thr residues and ubiquitination of ctnnb1 and its subsequent degradation by the proteasome. In the presence of Wnt ligand, ctnnb1 is not ubiquitinated and accumulates in the nucleus, where it acts as a coactivator for transcription factors of the TCF/LEF family, leading to activate Wnt responsive genes. Plays a key role in dorsoventral patterning: in prospective ventral blastomeres, its down-regulation by axin1 and axin2 leads to inhibit the Wnt signaling pathway, while in prospective dorsal blastomeres, degradation of axin results in stabilization and nuclear translocation of ctnnb1.