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Abstract
The sea bass follicle-stimulating hormone 5' flanking region (sbFSH[beta] 5' FR) was cloned and characterized in order to study the molecular mechanisms underlying transcriptional regulation of the sbFSH[beta] gene. Analysis of the ~3.5 kb of this region revealed the presence of several putative cis-acting elements, including steroid hormone response elements, cAMP response elements, pituitary-specific transcription factor response elements, activator protein-1 response elements and TATA sequence. Deleted constructs containing ~3.5 kb of the sbFSH[beta] 5' FR fused to a luciferase reporter gene were transiently transfected into human embryonic kidney (HEK 293) and mouse mature gonadotrope (L[beta]T2) cell lines. The sbFSH[beta] 5' FR was efficiently expressed under basal conditions in L[beta]T2 but not in HEK 293, pointing to both positive and negative regulatory elements. In order to elucidate the estrogen-mediated sbFSH[beta] transcriptional activity, in vitro treatments with 17[beta]-estradiol were carried out on primary cultures of pituitary cells and L[beta]T2 cells transiently expressing luciferase under the control of sbFSH[beta] 5' FR. Overall, these results demonstrate that 17[beta]-estradiol inhibits sbFSH[beta] gene expression directly at the level of the pituitary. However, it was also shown that estrogen did not induce changes of the sbFSH promoter-directed luciferase activity, suggesting that sbFSH[beta] 5'FR (~3.5 kb) activity is cell type dependent and its estrogen regulation could require cis-acting elements located upstream of the promoter region, which is characterized in this article.[PUBLICATION ABSTRACT]