Participates in the Wnt signaling pathway. Binds to DNA and acts as a repressor in the absence of ctnnb1-A and possibly ctnnb1-B, and as an activator in the presence of these proteins. Required early in development for the establishment of the dorsal body axis in response to maternal Wnt signaling. Also required during development of the CNS for the establishment of dorsal-ventral patterning in the prospective diencephalon. Interacts with csnk1e, ctnnb1-A, ctbp-B, dact1-A and gsk3b. May interact with ase and tle4-A. Phosphorylated. Phosphorylation by csnk1e promotes binding to ctnnb1-A while phosphorylation by gsk3b may reverse this effect. Belongs to the TCF/LEF family.