TEF-1 (transcription enhancer factor-1) is a member of a family of transcription factors that contain an evolutionarily conserved DNA binding domain (DBD), TEA/ATTS. TEF-1 was identified as a HeLa cell transcriptional activator that bound, via its TEA domain, to the GT-IIC and Sph enhancer elements. Comparison of various enhancers indicates that TEF-1 binds to highly degenerate DNA sequences and cooperatively interacts with tandem repeats of its binding sites, which increases its enhancer activity. However, the DNA binding activities of TEF-1 are modulated by sequences outside the DBD. The N-terminal basic portion of TEF-1 contains the DBD. The C-terminal portion contains the transactivation domain and a zinc finger-like motif that is thought to be involved in protein dimerization or interaction with additional transcription factors. TEF-1 induced transcription requires a limiting transcriptional intermediary factor (TIF) and a TATA-binding protein associated factor (hTAFIIs). Although TEF-1 is expressed ubiquitously during embryogenesis, its expression is limited to adult kidney, heart, brain, skeletal muscle, and lungs. Disruption of murine TEF-1 gene results in fetal death.