Incorporation of Drosophila TAF110 into the yeast TFIID complex does not permit the Sp1 glutamine-rich activation domain to function in vivo.

Abstract

Acidic activation domains function across eukaryotic species, and hence stimulate transcription by a conserved molecular mechanism. In contrast, glutamine-rich activation domains function in flies, mammals, and fission yeasts but not in the budding yeast Saccharomyces cerevisiae. The glutamine-rich activation domain of Sp1 interacts with TAF110, and it has been suggested that this interaction is important for transcriptional activation. S. cerevisiae does not contain a homologue of TAF110, suggesting a potential mechanism to account for the failure of glutamine-rich activation domains to stimulate transcription. Here, we have artificially recruited Drosophila TAF110 into the yeast TFIID complex by fusing it to yeast TBP. The resulting TFIID complex supports normal cell growth, but it is unable to mediate Sp1-dependent activation. Thus, the interaction of glutamine-rich activation domains with TAF110 is insufficient for transcriptional activation in vivo, indicating that other targets within the PolII machinery are necessary.