TRANSCRIPTION FACTOR MSY-1 REGULATES EXPRESSION OF THE MURINE GROWTH-HORMONE RECEPTOR GENE

Previous studies identified and partially characterized a 42-base pair regulatory element in the 5'-flanking region of the L1 transcript of the murine growth hormone (GH) receptor gene that interacted with both double- and single-stranded DNA-binding proteins. We present evidence that the double-stranded DNA-binding protein is NF-Y, a CCAAT box-bin ding protein. Experiments with a dominant negative form of NF-Y indica te that NF-Y does not play a direct role in regulating the activity of the FP42 element. A cDNA clone that specifically interacts with the u pper (coding) strand of the regulatory element was isolated by screeni ng a cDNA expression library using the Southwestern technique, DNA seq uencing, electrophoretic mobility shift assay, Southwestern blot analy sis, and supershift EMSA confirm the identity of the single-stranded b inding protein to be MSY-1, a DNA-binding protein that is evolutionary conserved from prokaryotes to eukaryote, Mapping of single-stranded D NA configurations reveals that MSY-1 can facilitate the formation of s ingle-stranded DNA regions in the GH receptor 5'-flanking region, Tran sient transfection experiments support the role of MSY-1 as a represso r of GH receptor gene activation. Southwestern blot analysis indicates that the levels of nuclear MSY-1 are decreased in the livers of pregn ant mice, suggesting a role for MSY-1 in the increased expression of t he GH receptor during pregnancy.