MECHANISM OF ASSEMBLY OF THE RNA POLYMERASE-II PREINITIATION COMPLEX - EVIDENCE FOR A FUNCTIONAL INTERACTION BETWEEN THE CARBOXYL-TERMINAL DOMAIN OF THE LARGEST SUBUNIT OF RNA POLYMERASE-II AND A HIGH MOLECULAR MASS FORM OF THE TATA FACTOR

Genetic evidence argues that the highly conserved carboxyl-terminal domain (CTD) of the largest subunit of RNA polymerase II functions directly in the regulation of transcription of many eukaryotic genes. The observation that partial deletion of the CTD of yeast RNA polymerase II reduces the ability of the enzyme to respond to signals from a variety of upstream activating sequences led to the proposal that the CTD plays a role in the dialogue between regulatory factors that bind upstream activating sequences and the "general" or "basal" transcription factors associated with RNA polymerase II at the promoter (Scafe, C., Chao, D., Lopes, J., Hirsch, J. P., Henry, S., and Young, R. A. (1990) Nature 347, 491-494). Biochemical evidence for an interaction of the CTD with specific components of the basal transcription apparatus, however, has been lacking. To identify target(s) for CTD action, we probed steps in assembly of the RNA polymerase II preinitiation complex with monoclonal antibodies specific for the CTD. Our findings reveal a novel interaction of the CTD with a high molecular mass form of the TATA factor. This interaction occurs during binding of RNA polymerase II to its promoter and requires the action of additional basal transcription factors; it is not observed when the single-subunit yeast transcription factor IID serves as the TATA factor.