DNA template and activator-coactivator requirements for transcriptional synergism by Drosophila bicoid.

The template and coactivator requirements for synergistic transcription directed by a single activator, Bicoid (BCD), bound to multiple sites have been determined. Mutagenesis studies in combination with protein binding experiments and reconstituted transcription reactions identified two independent activation domains of BCD that target different coactivator subunits (TAFII110 and TAFII60) of the basal transcription factor IID (TFIID). The presence of both coactivators is required for BCD to recruit the TATA binding protein (TBP)-TAF complex to the promoter and direct synergistic activation of transcription. Thus, contact between multiple activation domains of BCD and different targets within the TFIID complex can mediate transcriptional synergism.