Reconstitution of a complex transcriptional unit from the rainbow trout estrogen receptor gene in yeast Saccharomyces cerevisiae

In all oviparous, liver cells represent one of the main E2-target tissue where estrogen receptor (ER) constitutes the mediator of estrogen action. We previously showed that rainbow trout Oncorhynchus mykiss estrogen receptor (rtER) gene expression is up--regulated by estrogens, both in vivo and in hepatocyte cells. Other works showed a positive influence of cell-specific factors on the transcription state of this gene. The absence of nuclear receptors and a conserved transcriptional machinery between the yeast and higher eucaryotes makes yeast a valuable system for the determination of the factors implicated in the regulation of the rtER gene. In this report, we analyse a 0.2 kb fragment of this gene promoter in the yeast Saccharomyces cerevisiae, and show that the stable expression of rtER allows a high hormone-dependent transcriptional activation of this promoter. Moreover, the human-related Chicken Ovalbumin Upstream Promoter Transcription Factor 1 (hCoup-TFI) is able, as in mammalian cells, to enhance the autoregulation of the rtER gene promoter. Thus, this paper describes the reconstitution of a hormone-responsive transcription unit in yeast. Because of the multiple effects of xenobiotics on the reproductive axis, this system would be an interesting model to be tested for the screening of the effects of such molecules on the transcription state of the rtER gene.