A NOVEL TRANSCRIPTIONAL ACTIVATOR ORIGINATING FROM AN UPSTREAM PROMOTER IN THE HUMAN GROWTH-HORMONE GENE

Transcription of the human growth hormone gene can start in vitro and in vivo 197 base pairs upstream from the cap site of growth hormone mR NA (Courtois, S. J., Lafontaine, D., and Rousseau, G. G. (1992) J. Bio l. Chen. 267, 19736-19743). We have now characterized the mRNA that or iginates from this optional promoter and have found that it occurs in human hypophysis and placenta but not in 10 other tissues, This mRNA c ontains an open reading frame for a protein of 107 residues that share s sequence similarity with three domains of hepatic nuclear factor-1 a lpha. With antibodies directed against a peptide corresponding to the C terminus of this protein, immunoreactive material was detected in a subset of cells of the adenohypophysis. When fused to the DNA-binding domain of the yeast transcription factor GALE, the protein stimulated transcription from a GAL4-sensitive reporter gene in transiently trans fected pituitary and placental cells.