Controlling promoter strength and regulation in Saccharomyces cerevisiae using synthetic hybrid promoters.

A dynamic range of well-controlled constitutive and tunable promoters are essential for metabolic engineering and synthetic biology applications in all host organisms. Here, we apply a synthetic hybrid promoter approach for the creation of strong promoter libraries in the model yeast, Saccharomyces cerevisiae. Synthetic hybrid promoters are composed of two modular components-the enhancer element, consisting of tandem repeats or combinations of upstream activation sequences (UAS), and the core promoter element. We demonstrate the utility of this approach with three main case studies. First, we establish a dynamic range of constitutive promoters and in doing so expand transcriptional capacity of the strongest constitutive yeast promoter, P(GPD) , by 2.5-fold in terms of mRNA levels. Second, we demonstrate the capacity to impart synthetic regulation through a hybrid promoter approach by adding galactose activation and removing glucose repression. Third, we establish a collection of galactose-inducible hybrid promoters that span a nearly 50-fold dynamic range of galactose-induced expression levels and increase the transcriptional capacity of the Gal1 promoter by 15%. These results demonstrate that promoters in S. cerevisiae, and potentially all yeast, are enhancer limited and a synthetic hybrid promoter approach can expand, enhance, and control promoter activity.