TATA-binding protein-independent initiation: YY1, TFIIB, and RNA polymerase II direct basal transcription on supercoiled template DNA.

YY1 is a zinc finger transcription factor whose DNA-binding motif exhibits the properties of an initiator element. Only three factors were required to direct specific basal transcription on a supercoiled template DNA carrying the YY1 initiator: YY1, general transcription factor IIB, and RNA polymerase II. This minimal in vitro reaction did not require the TATA-binding protein (TBP). We propose that, under appropriate conditions, YY1 can function like TBP, as a factor that binds to the core promoter and recruits the polymerase to the initiation complex.