Ethanol-inducible gene expression using gld1 + promoter in the fission yeast Schizosaccharomyces pombe

In the fission yeast Schizosaccharomyces pombe, the gld1 ⁺ gene encoding glycerol dehydrogenase is repressed by glucose and induced by ethanol and 1-propanol. The promoter region of gld1 ⁺ was cloned into a multicopy vector designated as pEG1 for evaluation as an ethanol-inducible expression vector using EGFP as a model heterologous protein. Expression of EGFP was repressed in the presence of high glucose and induced in the presence of ethanol, low-glucose, and 1-propanol in the absence of glucose. Addition of ethanol to cells harboring pEG1–EGFP was found to be the most effective means for inducing EGFP production. Protein yields were found to increase in proportion to ethanol concentration. As a further test of effectiveness, secreted recombinant human growth hormone was produced using the pEG1 expression vector in medium containing glycerol and ethanol. The pEG1 gene expression system is an effective tool for the production of heterologous proteins under glucose-limiting conditions, including medium containing glycerol as a carbon source.