A DISTAL ENHANCER REGION IN THE HUMAN BETA-CASEIN GENE MEDIATES THE RESPONSE TO PROLACTIN AND GLUCOCORTICOID HORMONES

The 5' flanking region of the human beta-casein gene was investigated for the presence of regulatory sequences mediating the action of the l actogenic hormones prolactin and dexamethasone. DNA encompassing 9389 base pairs of the flanking region was isolated and a sequence comparis on performed with regulatory regions previously identified in the beta -casein gene of rodents and ruminants. The analysis revealed the prese nce of a distal region between -4700 and -4550 with a high percentage of identity to the bovine beta-casein enhancer region, and a proximal region between -1 and -200 similar to the proximal promoter regions fo und in rodents and ruminants. Reporter gene constructs under the contr ol of the distal or the proximal region of the human beta-casein gene were tested for their responsiveness to prolactin and dexamethasone. I n transfection experiments, the distal region functioned as a lactogen ic hormone inducible enhancer, whereas the proximal region exhibited l ow activity. In electromobility shift assays, multiple binding sites f or Stat5, CCAAT/enhancer-binding proteins, and Ets domain proteins wer e identified in the distal human enhancer. These transcription factors have already been demonstrated as important regulators of the transcr iption of milk protein genes in rodents. Thus, a common set of transcr iption factors appears to be required for the expression of the human beta-casein gene and of milk protein genes in other species. (C) 1998 Elsevier Science B.V. All rights reserved.