Identification and characterization of a consensus DNA binding element for the zinc finger transcription factor TIEG/EGRalpha.

TGFbeta-Inducible Early Gene (TIEG) and the alternatively-transcribed Early Growth Response Gene alpha (EGRalpha) share a Cys(2)His(2) three-zinc finger region with high homology to Sp1 within its zinc finger region. Three-zinc finger transcription factors bind to GC-rich sequences, with small variations in consensus sequence between subfamilies. In this work, a consensus sequence was identified for TIEG/EGRalpha by expressing and purifying the zinc finger region of the protein, and using this to select a binding site from a random oligonucleotide library by iterative cycles of nitrocellulose filter binding and PCR. A fusion of the TIEG/EGRalpha with the VP16 activation domain supported transcription from this site when cloned in front of a heterologous promoter. Mutational analysis of the binding site identified a GT-rich core (5'-GGTGTG-3') that was necessary for binding, with mutations outside of this region causing only a small to moderate decrease in binding.