The transcriptional induction of the chicken ovalbumin gene by steroid hormones is abolished by inhibitors of protein synthesis such as cycloheximide, suggesting that a labile protein mediates this process. A steroid-dependent regulatory element (SDRE) has been identified in the 5'- flanking region of the gene between -900 and -780 that is required for induction by steroids. Additional transfection experiments limit the 5'- border of the SDRE to the region between -892 and -864. To investigate whether any of the proteins binding to the SDRE are affected by estrogen or cycloheximide, protein binding was investigated using DNase I and exonuclease III footprinting and gel mobility shift assays. These experiments demonstrate that labile proteins bind to the sequences between -900 and -860 and between -810 and -820. Four oviduct nuclear proteins, including one of the labile proteins, binding to the SDRE prefer single-stranded DNA (ssDNA) in a sequence-specific manner. The binding activity of three of these ssDNA- binding proteins is increased in oviduct nuclear protein extracts from estrogen-treated chicks. These data suggest that induction of the ovalbumin gene is mediated by a complex collection of ssDNA- and double-stranded DNA- binding proteins whose activities are in turn regulated by their short half- lives or by estrogen.
|Number of pages
|Journal of Biological Chemistry
|Published - 1993