Mutations in the zinc-finger region of the yeast regulatory protein ADR1 affect both DNA binding and transcriptional activation.

The expression of the yeast ADH2 gene is controlled by the transcriptional activator ADR1, a zinc-finger protein that binds to an upstream activating sequence (UAS1) in the ADH2 promoter. We report here the isolation of seven mutations in the ADR1-5c allele, defining five different amino acid changes, that suppress the enhanced ADH2 expression caused by the ADR1-5c allele. Each of the mutations was shown to reduce the activation of ADH2 by a wild-type ADR1 gene, suggesting the mutations disrupt a domain important to the function of both the ADR1 and ADR1-5c proteins. All five amino acid changes occurred within the DNA-binding domain of ADR1 and were shown to severely inhibit the ability of ADR1 to bind UAS1 in vitro. These mutations were found, however, to also affect the ability of ADR1 to activate transcription independent of its ability to bind DNA. These results indicate that the DNA-binding region of ADR1 is involved in both transactivation and DNA binding.