LEF1 is a nuclear protein that is expressed in pre-B and T cells. It binds to a functionally important site in the T-cell receptor-alpha (TCRA; MIM 186880) enhancer and confers maximal enhancer activity. LEF1 belongs to a family of regulatory proteins that share homology with high mobility group protein-1 (HMG1; MIM 163905) (Waterman et al., 1991 [PubMed 2010090]; van Genderen et al., 1994 [PubMed 7958926]).[supplied by OMIM