A GLUTAMINE-RICH HYDROPHOBIC PATCH IN TRANSCRIPTION FACTOR-SP1 CONTACTS THE DTAF(II)110 COMPONENT OF THE DROSOPHILA TFIID COMPLEX AND MEDIATES TRANSCRIPTIONAL ACTIVATION

Activation of transcription by the promoter-specific factor Sp1 requir es coactivators that are tightly associated with the TATA-box-binding protein (TBP) in the TFIID complex. Recent work has shown that the two glutamine-rich activation domains of Sp1, A and B, can interact with at least one component of this complex, the TBP-associated factor dTAF (II)110. Here we report the mapping of a region of Sp1 with alternatin g glutamine and hydrophobic residues which is required for the interac tion with dTAF(II)110 and is important for mediating transcriptional a ctivation. Substitution of bulky hydrophobic residues within this regi on decreased both interaction with dTAF(II)110 and transcriptional act ivation in Drosophila cells. In contrast, mutation of glutamine residu es in this region had no effect. Thus, the strength of the Sp1-TAF int eraction correlates with the potency of Sp1 as a transcriptional activ ator, indicating that this activator-TAF interaction is an important p art of the mechanism of transcriptional activation. Sequence compariso n of three activation domains shown to bind dTAF(II)110 suggests that different activators that utilize dTAF(II)110 as a coactivator may sha re common sequence features that we have determined to be important fo r the Sp1-dTAF(II)110 interaction.