Usage of an intronic promoter for stable gene expression in Saccharomyces cerevisiae

To construct expression vectors capable of switching promoters under different metabolic circumstances to obtain stable gene expression.

In this study, we designed a series of constructs for the expression of the chicken lactate dehydrogenase (cldh) gene under the control of galactose-inducible GAL1 promoter and the high glucose-inducible HXT1 promoter in Saccharomyces cerevisiae. In one construct, the HXT1 promoter was placed between artificial splicing sequences to function as an intronic promoter. We checked all constructs for the usage of promoters by reverse transcriptional polymerase chain reaction and assayed the expression level of the reporter gene under different culturing conditions. In the presence of galactose, when the GAL1 promoter was linked with the intronic HXT1 promoter, the cldh gene showed 1.5-fold activity compared with single GAL1 promoter, while in the presence of glucose, the construct showed over twofold activity compared with that without splicing sequences.

The intronic HXT1 promoter could be induced by the presence of high glucose concentration.

This is the first report detailing the use of an intronic promoter in the construction of stable expression vectors and the novel system could serve as a model of expression vectors for fermentation or other purposes.