INTERACTION OF THE COOH-TERMINAL TRANSACTIVATION DOMAIN OF P65 NF-KAPPA-B WITH TATA-BINDING PROTEIN, TRANSCRIPTION FACTOR IIB, AND AND COACTIVATORS

We show that the transactivating COOH terminus of the p65 subunit of h uman transcription factor NF-kappa B directly binds the general transc ription factors TFIIB and TATA-binding protein (TBP) in vitro. Interac tion of p65 with TFIIB required the most COOH-terminal se quence repea t within TFIIB. A functional interaction of TFIIB with p65 was evident from assays in yeast cells. Cotransfection experiments in COS cells r evealed that only overexpression of TBP was able to further stimulate p65-dependent transactivation of a reporter gene. The coexpression of neither TBP nor TFIIB was able to relieve squelching, indicating the i nvolvement of additional factors in transactivation by p65. A cell-fre e assay using highly purified factors revealed a specific transcriptio nal stimulation through the COOH terminal activation domain of NF-kapp a B by at least one cofactor, PC1, isolated from HeLa cells. These dat a show that the potent acidic transactivation domains in the COOH term inus of p65 are able to functionally recruit various components of the basic transcription machinery as well as coactivators.