TCF7/TCF1: ProductsTCF7 (Transcription factor 7; also T cell factor 1/TCF1) is a 25 - 50 kDa member of the lymphoid enhancer binding factor family of proteins with 16 isoforms. It is expressed in thymocytes and mature T cells, and serves multiple purposes. In resting cells, TCF family members are transcriptional repressors, and are 25 - 32 kDa in size. Following activation, large TCF7 isoforms predominate (42 - 50 kDa), and serve a transcriptional activator function. Human TCF7 is 384 amino acids (aa) in length. This is likely an activating isoform that contains a beta-Catenin binding domain (aa 1 - 59), a DNA-binding HMG-box (aa 269 - 337), and an NLS (aa 344 - 348). The use of an alternate start site at Met116 seems to characterize repressor isoforms.