SEF1 binding is important for T cell specific enhancers of genes for T cell receptor-CD3 subunits.

A family of proteins, denoted SL3-3 enhancer factor 1 (SEF1), interacts with DNA sequences in the T cell specific enhancer of SL3-3 murine leukemia virus and in the enhancers of several other viruses. A putative SEF1 binding site was also identified in the T cell specific enhancer of the gene encoding the human T cell antigen receptor (TcR) associated CD3-epsilon polypeptide. In this study we show that the identified sequence is a strong SEF1 binding site, and that purified SEF1 proteins bind specifically to the sequence. We report also that the SEF1 binding site is important for T cell specific activation of transcription by the CD3-epsilon enhancer. We show that SEF1 binding sites are present also in the T cell specific enhancers of other subunits of the TcR-CD3 complex, and that SEF1 proteins appear to play a central role in the T cell specific expression of this set of enhancers.