ABSTRACT
Galactose is utilized by Saccharomyces cerevisiae through conversion to glucose-6-phosphate, which then enters the glycolytic pathway. Galactose enters the cell through a specific permease, encoded by GAL2. A strain with a disrupted GAL80 gene expresses the GAL genes constitutively. An artificial protein bearing an acidic 15-amino acid peptide linked to a DNA-binding fragment of GAL4 was generated. The GAL4 and GAL80 proteins interact directly by binding to one another. In some GAL4 mutants, this interaction is lost and the GAL genes expressed constitutively. GAL4 protein also stimulates in vitro transcription of a mammalian gene in a HeLa nuclear extract. The effector and reporter genes were introduced separately into Drosophila lines by P element transformation. New GAL transcriptional activators have been generated by fusing genomic DNA fragments of E. coli to the coding sequence of the DNA-binding portion of GAL4.
