Different TRE-related elements are distinguished by sets of DNA-binding proteins with overlapping sequence specificity

Several promoter elements with sequence similarity to the prototype TPA-responsive element (TRE) were compared by mobility-shift analyses. Activities within whole cell extracts were identified that bind to the TRE-like elements in the collagenase, the somatostatin, and the c-jun promoters. The corresponding factors appeared to differ in their degree of selectivity for these TRE-like sequences. One protein species bound equally well to all TREs. In addition, a subset of specific activities recognised only the somatostatin and the c-jun-derived element and one DNA-protein complex had exclusive specificity for the TRE present in the c-jun promoter. By antibody 'supershift' assays some of the protein components of the specific complexes were identified as CREB- and ATF-related products. Based on these data we postulate that bZip protein dimers differ in their ability to tolerate variations from the canonical TRE sequence. We propose that TRE-like promoter elements are distinguished by this ability to bind to different subsets of a family of related transcription factors.