Conservation of glutamine-rich transactivation function between yeast and humans

Several eukaryotic transcription factors such as Sp1 or Oct1 contain glutam ine-rich domains that mediate transcriptional activation. In human cells, p romoter-proximally bound glutamine-rich activation domains activate transcr iption pearly in the absence of acidic type activators bound at distal enha ncers, but synergistically stimulate transcription with these remote activa tors. Glutamine-rich activation domains were previously reported to also fu nction in the fission yeast Schizosaccharomyces pombe but not in the buddin g yeast Saccharomyces cerevisiae, suggesting that budding yeast lacks this pathway of transcriptional activation. The strong interaction of an Spl glu tamine-rich domain with the general transcription factor TAF(II)110 (TAF(II )130), and the absence of any obvious TAF(II)110 homologue in the budding y east genome, seemed to confirm this notion. We reinvestigated the phenomeno n by reconstituting in the budding yeast an enhancer-promoter architecture that is prevalent in higher eukaryotes but less common in yeast. Under thes e conditions, we observed that glutamine-rich activation domains derived fr om both mammalian and yeast transcription factors activated only poorly on their own but strongly synergized with acidic activators hound at the remot e enhancer position, The level of activation by the glutamine-rich activati on domains of Sp1 and Oct1 in combination with a remote enhancer was simila r in yeast and human cells. We also found that mutations in a glutamine-ric h domain had similar phenotypes in budding yeast and human cells. Our resul ts show that glutamine-rich activation domains behave very similarly in yea st and mammals and that their activity in budding yeast does not depend on the presence of a TAF(II)110 homologue,