Role of Core Promoter Structure in Assembly of the RNA Polymerase II Preinitiation Complex: A Common Pathway for Formation of Preinitiation Intermediates at Many TATA and TATA-less Promoters

Efforts to understand the impact of core promoter architecture on the mechanism of transcription initiation by RNA polymerase II have been hampered by lack of well defined, reconstituted transcription systems responsive both to efficiently transcribed consensus and near consensus TATA box-containing promoters and to considerably weaker TATA-less promoters. In this report, we investigate the influence of core promoter structure on the mechanism of assembly of the RNA polymerase II preinitiation complex using a highly purified, holoTFIID-dependent transcription system that permits sensitive measurement of transcription initiation from a wide variety of TATA and TATA-less promoters in the absence of transactivators. A direct comparison of the requirements for formation of stable preinitiation intermediates at these promoters led to the discovery that, whereas holoTFIID binds avidly to the consensus TATA- and strong initiator-containing adenovirus major late (AdML) promoter to form the first stable intermediate on the pathway leading to formation of the complete preinitiation complex, it binds poorly not only to TATA-less promoters but also to promoters with consensus or near consensus TATA elements. With the exception of the AdML promoter, formation of stable preinitiation intermediates at each of the promoters tested was found to be strongly dependent on RNA polymerase II, holoTFIID, and TFIIB and was stimulated by TFIIF. Based on these observations, we suggest that RNA polymerase II assembles with many TATA and TATA-less promoters by a common pathway.