Functional distinctions between yeast TATA elements

Although the yeast his3 promoter region contains two functional TATA elements, TR and TC, the GCN4 and GAL4 upstream activator proteins stimulate transcription only through TR. In combination with GAL4, an oligonucleotide containing the sequence TATAAA is fully sufficient for TR function, whereas almost all single-base-pair substitutions of this sequence abolish the ability of this element to activate transcription. Further analysis of these and other mutations of the TR element led to the following conclusions. First, sequences downstream of the TATAAA sequence are important for TR function. Second, a double mutant, TATTTA, can serve as a TR element even though the corresponding single mutation, TATTAA, is unable to do so. Third, three mutations have the novel property of being able to activate transcription in combination with GCN4 but not with GAL4; this finding suggests that activation by GCN4 and by GAL4 may not occur by identical mechanisms. From these observations, we address the question of whether there is a single TATA-binding factor required for the transcription of all genes.