Promoter specificity of the two transcriptional activation functions of the human oestrogen receptor in yeast.

We have previously demonstrated that the human oestrogen receptor (hER) contains two transcriptional activation functions located in the N-terminal region (TAF-1) and in the hormone binding domain (TAF-2), which can act both independently and synergistically in a promoter- and cell-specific manner in animal cells. We have also demonstrated that hER can activate transcription from chimaeric oestrogen-responsive GAL1 promoters in yeast, and shown that transcriptional activation was due to TAF-1, whereas TAF-2 showed little, if any, transcriptional activity on these promoters. By using a more complex promoter derived from the URA3 gene, we now show that TAF-2 is also active in yeast, and that the activities of TAF-1 and TAF-2 are promoter-context-specific in yeast. We also confirm that the agonistic activity of 4-hydroxytamoxifen (OHT) can be ascribed to the activity of TAF-1.