Nondissociation of GAL4 and GAL80 in vivo after galactose induction.

Transcription of galactose-inducible genes in yeast is regulated by interaction between the activator protein GAL4 and the negative regulatory protein GAL80. It has been suggested that GAL80 binds to and represses GAL4 under uninduced conditions and dissociates from GAL4 on induction. However, the possibility that GAL80 remains associated with GAL4 after induction has not been ruled out. Experiments to discriminate between these two models were performed and revealed that GAL80 stays bound after induction.