Cloning and characterization of the 5′-flanking region of the rat estrogen receptor β gene

In the rat, estrogen receptor (ER) β is preferentially expressed in the ovary and the prostate gland where it is transcriptionally regulated by testosterone. A single 5′-end of rERβ cDNA was identified in these tissues by the 5′-RACE analysis in the present study. The transcription starting site was predicted at −335 from the translation starting signal (ATG), and a 640 bp section of the 5′-flanking region of the gene was cloned. Luciferase reporter assays revealed this region to be responsible for cell-specific promoter activity and successive deletion analyses indicated that only 98 bp were sufficient for basic promoter activity as well as for testosterone-dependent transcription. The sequence of the determined region found to demonstrate high homology with the mouse ERβ promoter with more than 80% identity between positions −1 and −550. The rat region of −30/−110 also showed good homology with 69% identity to corresponding section of the human promoter. Putative cis-acting elements, USF/Arnt and AML1a, were found in common in the promoter regions of three species. The present study thus demonstrated the 5′-flanking region of the rERβ gene to be a functional promoter.