The Glutamine-Rich Activation Domains of Human Sp1 Do Not Stimulate Transcription in Saccharomyces cerevisiae

Eukaryotic transcriptional activators have been classified on the basis of the characteristics of their activation domains. Acidic activation domains, such as those in the yeast GAL4 or GNC4 proteins and the herpes simplex virus activator VP16, stimulate RNA polymerase II transcription when introduced into a variety of eukaryotic cells. This species interchangeability demonstrates that the mechanism by which acidic activation domains function is highly conserved in the eukaryotic kingdom. To determine whether such a conservation of function exists for a different class of activation domain, we have tested whether the glutamine-rich activation domains of the human transcriptional activator Sp1 function in the yeast Saccharomyces cerevisiae. We report here that the glutamine-rich domains of Sp1 do not stimulate transcription in S. cerevisiae, even when accompanied by human TATA-box binding protein (TBP) or human-yeast TATA-box binding protein hybrids. Thus, in contrast to the case for acidic activation domains, the mechanism by which glutamine-rich domains stimulate transcription is not conserved between S. cerevisiae and humans.