Fig. 4.

TCF and β-catenin and its co-activator complexes in the nucleus. Upon Wnt signaling activation, β-catenin translocates to the nucleus and binds to TCF. The TCF/β-catenin complex recruits many co-activators required for the initiation and maintenance of active gene expression. These include for example, but are not restricted to, BCL9 (Legless/Lgs) and Pygopus (Pygo), interacting within the Arm repeat region of β-catenin (red region of β-catenin in schematic), and Mediator (for transcription initiation), p300/CBP, MLL1/2 histone methyltransferase and BRG (for chromatin modification (SWI/SNF) in the C-terminal transactivation (TA) region of β-catenin. Note that while the central Arm repeats region of β-catenin (red) associates with TCF, and the more N-terminal Arm-repeats bind to BCL9, most of other co-activator complexes interact with β-catenin in its C-terminal TA domain, creating a dazzling interplay between β-catenin and the transcriptional apparatus and the chromatin. Note that no nuclear interactors have thus far been identified for the most N-terminal region of β-catenin (N-terminal to the Arm repeats, orange and yellow in schematic).