HIGHLY EFFICIENT TRANSACTIVATION BY THE YEAST KLUYVEROMYCES-LACTIS TRANSCRIPTION FACTOR LAC9 AND ITS INHIBITION BY THE NEGATIVE REGULATOR GAL80 IN MAMMALIAN-CELLS

Expression of the LAC9 gene from the yeast Kluyveromyces lactis in Hep G2 human hepatoblastoma cells efficiently induced luciferase expressio n from reporter plasmids containing the four LAC9 binding sites from t he K. lactis GAL1 - GAL10 gene linked to a basal promoter. Induction w as approximately 100fold and was dependent on the presence of the UAS sequence and an intact reading frame in the LAC9 gene. Additional cotr ansfection of constructs expressing the K. lactis GAL80 gene reduced l uciferase activity by up to 98%. This inhibition was not affected by a ddition of 14mM galactose to the medium. No further yeast-specific fac tors appear necessary for efficient inhibition of LAC9 by GAL80, but a dditional gene products may be required for activation by galactose.