Participates in the Wnt signaling pathway and modulates MYC expression by binding to its promoter in a sequence-specific manner. Acts as a repressor in the absence of CTNNB1, and as activator in its presence. Activates transcription from promoters with several copies of the Tcf motif 5'-CCTTTGATC-3' in the presence of CTNNB1. TLE1, TLE2, TLE3 and TLE4 repress transactivation mediated by TCF7L2/TCF4 and CTNNB1. Expression of dominant-negative mutants results in cell-cycle arrest in G1. Necessary for the maintenance of the epithelial stem-cell compartment of the small intestine. {ECO:0000269|PubMed:12408868, ECO:0000269|PubMed:12727872, ECO:0000269|PubMed:19443654, ECO:0000269|PubMed:22699938, ECO:0000269|PubMed:9727977}. This is the function of TCF7L2 (transcription factor 7 like 2, ENSG00000148737).