THE 2 ACTIVATION DOMAINS OF THE CCAAT-BINDING FACTOR CBF INTERACT WITH THE DTAF(II)110 COMPONENT OF THE DROSOPHILA TFIID-COMPLEX

The CCAAT-binding factor CBF is a heterotrimeric transcription factor that specifically binds to CCAAT sequences in many eukaryotic genes. P revious studies have shown that CBF contains two transcription activat ion domains: a glutamine-rich, serine-threonine-rich domain present in the CBF-B subunit and a glutamine-rich domain in the CBF-C subunit, I n this study, by using a series of deletion mutations of CBF-B and CBF -C in transcription assay in vitro, we further delineated smaller segm ents in these domains that were sufficient to support transcriptional activation by CBF. To test whether transcription activation by CBF req uires co-activators, we examined the interaction between CBF and dTAF1 10, a component of the Drosophila TFIID complex. Recent work has demon strated that glutamine-rich domains of the Spl transcription factor in teract with dTAF110 and that this interaction has an important role in mediating transcription activation. Here we first demonstrate in a di rect interaction assay in vitro that CBF binds dTAF110. By using a yea st two-hybrid system we show that both of the transcription activation domains of CBF interact with dTAF110. A deletion analysis suggests th at a segment of CBF-B needed for transcription activation is also invo lved in interaction with dTAF110. In CBF-C the C-terminal portion of t he molecule seems to be needed for these two activities. Our results s uggest that TAF110 might represent one of the co-activators that media te transcriptional activation by CBF.