Cooperation between core promoter elements influences transcriptional activity in vivo

Core promoters for RNA polymerase II frequently contain either (or both) of two consensus sequence elements, a TATA box and/or an initiator (Inr). Using test promoters consisting of prototypical TATA and/or Inr elements, together with binding sites for sequence-specific activators, we have analyzed the function of TATA and Inr elements in vivo. In the absence of activators, the TATA element was significantly more active than the Inr, and the combination of elements was only slightly more effective than the TATA-only promoter. In the presence of any of several coexpressed activator proteins, the TATA elements was again most active, but here addition of the Inr allowed significant increases in activity, indicating a cooperative interaction between the two elements. An interesting exception was observed with the activator Sp1, which was more effective with the Inr-only promoter, and addition of a TATA box did not enhance activity. Finally, in all cases the TATA plus Inr promoters were found to be partially or completely resistant to the dominant negative effects of a transcription factor TFIIB mutant previously shown to interfere with expression from TATA-only promoters. This result strengthens the conclusion that TATA and Inr elements can cooperate in vivo.