Carbon source-dependent transcriptional regulation of the QCR8 gene in Kluyveromyces lactis - Identification of cis-acting regions and trans-acting factors in the KIQCR8 upstream region

The QCR8 gene of the yeast Kluyveromyces lactis is transcriptionally regula ted by the carbon source in the growth medium. Deletion analysis of the KlQ CR8 promoter shows that an element located between -144 bp and -113 bp spec ifically controls induction of QCR8 gene expression on non-fermentable carb on sources. Specific and differential protein-binding to the activating seq uence was observed with extracts from glucose- and ethanol/glycerol-grown c ells. Induction of the reporter gene and protein-binding was dependent on t he presence of a functional KlCAT8 gene, suggesting that, in K. lactis, KlC at8p acts in the transcriptional regulation of respiratory function. The ac tivating element contains no other known regulatory sites but two elements required for RNA holoenzyme functioning, raising the intriguing possibility of carbon source-dependent regulation by a subunit of the RNA polymerase h oloenzyme in K. lactis.