THE N-TERMINAL DOMAIN OF THE HUMAN TATA-BINDING PROTEIN PLAYS A ROLE IN TRANSCRIPTION FROM TATA-CONTAINING RNA-POLYMERASE-II AND RNA-POLYMERASE-III PROMOTERS

In eukaryotes, the TATA box binding protein (TBP) is an integral compo nent of the transcription initiation complexes of all three classes of nuclear RNA polymerases. In this study we have investigated the role of the N-terminal region of human TBP in transcription initiation from RNA polymerase (Pol) I, II and III promoters by using three monoclona l antibodies (mAbs). Each antibody recognizes a distinct epitope in th e N-terminal domain of human TBP. We demonstrate that these antibodies differentially affect transcription from distinct classes of promoter s. One antibody, mAb1C2, and a synthetic peptide comprising its epitop e selectively inhibited in vitro transcription from TATA-containing, b ut not from TATA-less promoters, irrespective of whether they were tra nscribed by Pol II or Pol m. Transcription by Pol I, on the other hand , was not affected. Two other antibodies and their respective epitope peptides did not affect transcription from any of the promoters tested . Order of addition experiments indicate that mAb1C2 did not prevent b inding of TBP to the TATA box or the formation of the TBP-TFIIA-TFIIB complex but rather inhibited a subsequent step of preinitiation comple x formation. These data suggest that a defined region within the N-ter minal domain of human TBP may be involved in specific protein- protein interactions required for the assembly of functional preinitiation co mplexes on TATA-containing, but not on TATA-less promoters.