The DNA target sequence influences the dependence of the yeast transcriptional activator Gcn4 on co-factors.

The yeast transcriptional activator Gcn4 requires the Ada2/Gcn5/Ada3 co-activator complex to exert part of its activation potential. Here we show that the sequence of the DNA target modulates the function of Gcn4 by modifying this requirement. Promoter configurations were generated that rendered Gcn4-induced transcription either completely dependent or completely independent of the Ada2/Gcn5/Ada3 complex. The topological constraints imposed by these configurations suggest that Gcn4 makes multiple contacts with the basic transcription machinery that are subject to modification by the incident DNA target. We propose that these modifications further determine the direction on the chromosome in which an otherwise symmetric, dimeric transcription factor will activate.