INVOLVEMENT OF THE TRANSCRIPTION FACTOR-IID PROTEIN COMPLEX IN GENE ACTIVATION BY THE N-TERMINAL TRANSACTIVATION DOMAIN OF THE GLUCOCORTICOID RECEPTOR IN-VITRO

HeLa cell nuclear extracts were used to study the mechanism of activat ion of RNA polymerase II-mediated transcription by the N-terminal tran sactivation domain (tau 1) Of the glucocorticoid receptor in vitro, Wh en fused to the Ga14 DNA-binding domain, the tau 1 domain activated tr anscription approximately 9-fold in HeLa nuclear extracts, Using heat treatment to inactivate transcription factor IID (TFIID) in the extrac t, it was shown that the addition of purified TFIID complex, but not t he TATA-binding protein alone, was sufficient to restore this level of activation, The tau 1 domain was shown to interact directly with the TFIID complex, This interaction was markedly reduced by a mutation in the tau 1 domain that reduces its activity. Furthermore, the interacti on was specific for the TFIID complex, since no interaction was seen w ith TFIIIB, an analogous protein complex involved in RNA polymerase II I transcription, The tau 1 domain was further shown to interact with t he TATA-binding protein subunit of the TFIID complex, These results su ggest a mechanism by which the GB tau 1 domain might contribute to gen e activation by recruitment of the TFIID complex to target promoters.