Novel elements in the uteroglobin promoter are a functional target for prolactin signaling

To quantify uteroglobin (UG) gene expression, varying lengths of 5' flanking sequence were subcloned into a luciferase reporter plasmid and introduced into HRE-H9 uterine epithelial cells. In response to estrogen, prolactin (PRL) and progesterone, transcriptional activity was maximal for the full-length construct, pUG3.1-LUC. Transcriptional activity was reduced (P < 0.05) by the removal of the progesterone receptor binding site, tested with pUG2.3-LUC, and eliminated (P < 0.05) by the removal of the remaining 5' flanking sequences, tested with pUG0.1-LUC. When the effects of PRL +/- progesterone were evaluated, progesterone alone increased (P < 0.05) the transcriptional activity of pUG3.1-LUC, and the deletion mutant, pUG3.1 Delta RUSH-LUC. Transcription of pUG3.1-LUC was further increased (P < 0.05) by PRL + progesterone. However, deletion of the proximal promoter region -170/-85: tested with pUG3.1 Delta RUSH-LUC, eliminated (P > 0.05) the PRL effect. These data support the speculation that RUSH proteins which bind to this region of the promoter play an important regulatory role in PRL signal transduction. (C) 1997 Elsevier Science Ireland Ltd.