Engineering an Efficient Expression Using Heterologous GAL Promoters and Transcriptional Activators in Saccharomyces cerevisiae

Galactose-inducible ( GAL ) promoters have been widely used in metabolic engineering in Saccharomyces cerevisiae for production of valuable products. Endogenous GAL promoters and GAL transcription factors have often been engineered to improve GAL promoter activities. Heterologous GAL promoters and GAL activator (Gal4p-like transcriptional activators), although existing in other yeasts or fungi, have not been well explored. In this study, we comprehensively characterized the activation effects of Gal4p activators from different yeasts or fungi on a variant of GAL promoters. Overexpressing endogenous Gal4p driven by P HHF1 increased the activities of native P GAL1 and heterologous P Sk GAL2 by 131.20% and 72.45%, respectively. Furthermore, eight transcriptional activators from different organisms were characterized and most of them exhibited functions that were consistent with Sc Gal4p. Expression of Kl Lac9p from Kluyveromyces lactis further increased the activity of P Sc GAL1 and P Sk GAL2 by 41.56% and 100.63%, respectively, compared to Sc Gal4p expression, and was able to evade Gal80p inhibition. This optimized GAL expression system can be used to increase the production of β-carotene by 9.02-fold in S. cerevisiae . Our study demonstrated that a combination of heterologous transcriptional activators and GAL promoters provided novel insights into the optimization of the GAL expression system.