Transcriptional Activation by Bas1 and Bas2 in Yeast

Georgetown University, Washington DC

Investigators

Abstract

Cells must adapt to the changing conditions in their environment by sensing external conditions and signaling these conditions to alter expression of genes whose products permit growth or survival under the new conditions. In general, transcription factors are the recipients of the signals and their activity is increased or decreased dependent upon conditions. Transcription factors, in turn, bind to specific DNA sites and recruit components of the transcriptional machinery including the general transcription factors, coactivators, chromatin remodeling complexes and RNA polymerase II. Frequently, gene expression depends upon multiple activators functioning in a combinatorial manner to specifically stimulate transcription. The ADE genes of Saccharomyces are a system we have been studying to determine how a purine limitation signal is detected and transmitted to the activators Bas1 and Bas2. Expression of the ADE genes is inherently combinatorial as both activators are required. However, the individual roles that these factors play in activation function are unknown. Furthermore, although Bas1 and Bas2 are required to stimulate expression of the ADE genes, there is evidence that the binding and expression conditions vary in the different promoter contexts, suggesting that recruitment of the components of the transcriptional machinery is also different. This research will investigate the roles that the activators Bas1 and Bas2 play during transcription of the ADE genes. The goal is to understand the underlying mechanisms that permit these activators to respond to a purine limitation signal and to promote transcription. While the focus of this project is on ADE gene regulation by Bas1 and Bas2, these studies will add to our understanding of combinatorial mechanisms for transcription regulation.