EFFICIENT RECRUITMENT OF TFIIB AND CBP-RNA POLYMERASE-II HOLOENZYME BY AN INTERFERON-BETA ENHANCEOSOME IN-VITRO

The transcriptional activity of an in vitro assembled human interferon -beta gene enhanceosome is highly synergistic, This synergy requires f ive distinct transcriptional activator proteins (ATF2/c-JUN, interfero n regulatory factor 1, and p50/p65 of NF-kappa B), the high mobility g roup protein HMG I(Y), and the correct alignment of protein-binding si tes on the face of the DNA double helix. Here, we investigate the mech anisms of enhanceosome-dependent transcriptional synergy during preini tiation complex assembly in vitro. We show that the stereospecific ass embly of the enhanceosome is critical for the efficient recruitment of TFIIB into a template-committed TFIID-TFIIA USA (upstream stimulatory activity complex) and for the subsequent recruitment of the RNA polym erase II holoenzyme complex. In addition, we provide evidence that rec ruitment of the holoenzyme by the enhanceosome is due, at least in par t, to interactions between the enhanceosome and the transcriptional co activator CREB, cAMP responsive element binding protein (CBP), These s tudies reveal a unique role of enhanceosomes in the cooperative assemb ly of the transcription machinery on the human interferon-beta promote r.