The TBP-inhibitory domain of TAF145 limits the effects of nonclassical transcriptional activators

Many genes in bacteria and eukaryotes are activated by "regulated recruitment" [1]. According to that picture, a transcriptional activator binds cooperatively to DNA with the transcriptional machinery, and the constitutively active polymerase then spontaneously transcribes the gene. An important class of experiments that helped develop this model is called the "activator by-pass" experiment [2-7]. In one version of such an experiment, the ordinary activator-transcriptional machinery interaction is replaced by a heterologous interaction. For example, fusing any of several DNA binding domains to Gal11, a component of the yeast mediator complex [2,4,5], creates a powerful activator of genes bearing the corresponding DNA binding sites. Here, we describe a simple modification of the yeast transcriptional machinery that extends the success of similar experiments involving other mediator components. The results reinforce parallels between regulation of enzymes involved in transcription and in other cellular processes.