TRANSCRIPTIONAL REGULATION OF EXPRESSION OF THE RAINBOW-TROUT ALBUMINGENE BY ESTROGEN

Estrogens modulate the expression of many liver-specific genes in ovip arous species. For instance, expression of the estrogen receptor and v itellogenin genes is strongly up-regulated by estradiol in rainbow tro ut liver. Using hepatocyte primary cultures, we demonstrate that trout albumin (Alb) gene is also regulated by this hormone. Indeed, treatme nt of hepatocytes with 1 mu M estradiol led, after 24 h, to a dramatic decrease in Alb mRNA level. To investigate the mechanism of this down -regulation, run-off experiments were performed and mRNA half-lives we re determined in the presence and absence of estradiol. The results sh ow that the down-regulation of Alb mRNA expression by estrogens occurs only at the transcriptional level.