T-cell factor (TCF-1) and lymphoid enhancer-binding factor (for LEF-1, also designated TCF-1?) compose a family of DNA-binding transcriptional activators that are essential for lymphoid cell development. These transcription factors are activated by the Wnt-1 and Wingless pathways and are characterized by the presence of a conserved protein motif, the high mobility group (HMG) 1 box, which mediates DNA binding. LEF-1, TCF-1, and two other family members, TCF-3 and TCF-4, directly bind to cytosolic beta-catenin and facilitate its translocation to the nucleus, where these complexes induce expression of Wnt target genes.