A system for temperature-controlled expression of a foreign gene with dual mode in Saccharomyces cerevisiae

Natural and modified promoters for tailored metabolic engineering of the yeast Saccharomyces cerevisiae

The ease of highly sophisticated genetic manipulations in the yeast Saccharomyces cerevisiae has initiated numerous initiatives towards development of metabolically engineered strains for novel applications beyond its traditional use in brewing, baking, and wine making. In fact, baker's yeast has become a key cell factory for the production of various bulk and fine chemicals. Successful metabolic engineering requires fine-tuned adjustments of metabolic fluxes and coordination of multiple pathways within the cell. This has mostly been achieved by controlling gene expression at the transcriptional level, i.e., by using promoters with appropriate strengths and regulatory properties. Here we present an overview of natural and modified promoters, which have been used in metabolic pathway engineering of S. cerevisiae. Recent developments in creating promoters with tailor-made properties are also discussed.

Growth rate influences MF alpha 1 promoter activity in MAT alpha Saccharomyces cerevisiae

The signal sequences of the MF alpha 1 prepro alpha-factor gene are frequently used to direct secretion of heterologous proteins from Saccharomyces cerevisiae. They are often employed together with the MF alpha 1 promoter in secretion vectors, such that this promoter directs the transcription of many heterologous gene cassettes in yeast. Most of the existing literature indicates that the MF alpha 1 promoter is constitutive in MAT alpha cells, although some data suggests that it may be more active in respiratory or late logarithmic fermentative cultures. To identify whether there is a growth rate or medium control over MF alpha 1 promoter activity a strain was constructed with an integrated MF alpha 1 promoter-beta-galactosidase (lacZ) reporter gene fusion. Intracellular beta-galactosidase of this strain during batch culture on glucose, raffinose and acetate showed that MF alpha 1 promoter activity was higher during respiratory growth on acetate as compared to more rapid fermentative growth on glucose or raffinose, a result that might indicate this activity being inversely related to growth rate. Chemostat culture confirmed that growth rate does indeed influence MF alpha 1 promoter activity in glucose-grown cells, the activity of this promoter increasing 2- to 2.5-fold as dilution (growth) rates were reduced from maximal values to 0.2 h-1, but then decreasing with the further decreases in dilution rate needed for fully respiratory growth. Thus a promoter generally thought to be constitutive in MAT alpha cells is nevertheless subject to a complex growth rate control.