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 wh ere estrogen receptor (ER) constitutes the mediator of estrogen action. We previously showed that rainbow trout Oncorhynchus mykiss estrogen receptor (rtER) gene expression is upregulated by estrogens, both in vivo and in hep atocyte cells. Other works showed a positive influence of cell-specific fac tors 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 t he determination of the factors implicated in the regulation of the rtER ge ne. In this report, we analyse a 0.2 kb fragment of this gene promoter in t he yeast Saccharomyces cerevisiae, and show that the stable expression of r tER allows a high hormone-dependent transcriptional activation of this prom oter. Moreover, the human-related Chicken Ovalbumin Upstream Promoter Trans cription Factor I (hCoup-TFI) is able, as in mammalian cells, to enhance th e autoregulation of the rtER gene promoter. Thus, this paper describes the reconstitution of a hormone-responsive trans cription unit in yeast. Because of the multiple effects of xenobiotics on t he reproductive axis, this system would be an interesting model to be teste d for the screening of the effects of such molecules on the transcription s tate of the rtER gene.