THE DNA TARGET SEQUENCE INFLUENCES THE DEPENDENCE OF THE YEAST TRANSCRIPTIONAL ACTIVATOR GCN4 ON COFACTORS

The yeast transcriptional activator Gcn4 requires the Ada2/Gcn5/Ada3 c o-activator complex to exert part of its activation potential, Here we show that the sequence of the DNA target modulates the function of Gc n4 by modifying this requirement. Promoter configurations were generat ed that rendered Gcn4-induced transcription either completely dependen t or completely independent of the Ada2/Gcn5/Ada3 complex. The topolog ical constraints imposed by these configurations suggest that Gcn4 mak es multiple contacts with the basic transcription machinery that are s ubject to modification by the incident DNA target. We propose that the se modifications further determine the direction on the chromosome in which an otherwise symmetric, dimeric transcription factor will activa te.