Activating regions of yeast transcription factors must have both acidic and hydrophobic amino acids.

Two similarities among transcriptional activating regions of many eukaryotic transcription factors, like those from GAL4, GCN4, and VP16, are that they have a net negative charge, and that many of them can potentially form amphipathic alpha-helices with acidic amino acids on the hydrophilic face. Based on these similarities, E. Giniger and M. Ptashne previously designed a short peptide (AH) which is predicted to have the potential to form a negatively charged amphipathic alpha-helix; AH was able to mediate transcription activation in yeast when it was attached to the DNA binding and dimerization portion of GAL4 [GAL4(1-147)]. This paper describes screening of a pool of AH derivatives containing randomized amino acids fused to GAL4(1-147) and to an analogous region of LexA [LexA(1-87)] in yeast strains. Results suggest that both acidic and hydrophobic amino acids are critical features of activating regions--these results are consistent with the model that activating regions often form amphipathic alpha-helices. This work is novel because hydrophobic amino acids are also shown to be important in activating regions of yeast transcription factors.