In the canonical Wnt signaling pathway, β-catenin activates target genes through its interactions with Tcf/Lef-family transcription factors and additional transcriptional coactivators. The crystal structure of ICAT, an inhibitor of β-catenin-mediated transcription, bound to the armadillo repeat domain of β-catenin, has been determined. ICAT contains an N-terminal helilical domain that binds to repeats 11 and 12 of β-catenin, and an extended C-terminal region that binds to repeats 5-10 in a manner similar to that of Tcfs and other β-catenin ligands. Full-length ICAT dissociates complexes of β-catenin, Lef-1, and the transcriptional coactivator p300, whereas the helical domain alone selectively blocks binding to p300. The C-terminal armadillo repeats of β-catenin may be an attractive target for compounds designed to disrupt aberrant β-catenin-mediated transcription associated with various cancers.
Daniels, D. L., & Weis, W. I. (2002). ICAT inhibits β-catenin binding to tcf/lef-family transcription factors and the general coactivator p300 using independent structural modules. Molecular Cell, 10(3), 573–584. https://doi.org/10.1016/S1097-2765(02)00631-7