Ligand activated hPR modulates the glycodelin promoter activity through the Sp1 sites in human endometrial adenocarcinoma cells

Human endometrium produces glycodelin-A (GdA). The GdA mRNA is highly expre ssed in progestin-sensitized human endometrial glandular epithelial cells. The mechanism of GdA gene expression, however, is not clear. To understand the cell specific GdA gene transcription, our first approach was to identif y the cis-element in the GdA promoter using transfection assay in a human e ndometrial adenocarcinoma cell line (HEC-1B, a cell line originally derived from the glandular component of the endometrium). The GdA promoter (-1900 to + 20 bp) was linked to the luciferase reporter gene to construct p1900Lu c, along with two shorter promoter constructs, p1100Luc and p304Luc. Deleti on analysis showed that the basal promoter activity was derived from the le gion between - 304 to + 20 bp. This region contains three putative Spl bind ing sites (Sp1-1, - 243 to - 238 bp; Sp1-2. - 207 to - 202 bp; and Sp1-3, - 56 to - 49 bp). Mutation analysis at the Spl sites showed that p304Spm2Luc and p304Spm3Luc reduced the activity by 80%, while p304Spm1-2-3Luc reduced the activity by 95% . Sp1-1 mutation, however, had no effect. These result s showed that two of the three Spl cis-elements mediate the basal promoter activity of the GdA gene. Electrophoretic gel mobility shift showed that at least two specific binding proteins in the nuclear extracts of HEC-1B cell s bound to the oligo containing Sp1-2 or Sp1-3 cis-element. Spl antibody re duced the specific binding complex by 70% suggesting that Spl transcription factor regulates GdA gene expression. In addition, over expression of Spl increased the promoter activity. To determine whether progestin would modul ate the promoter activity, HEC-1B cells were transfected with p304Luc and w ith progesterone receptor (either hPR-A or hPR-B) expression vector. Medrox yprogesterone acetate increased the promoter activity (3-fold) derived from p304Luc but not from the mutant, p304Spm1-2-3Luc. In contrast. the promote r activity was slightly reduced in cells treated with estradiol and co-tran sfected with estrogen receptor expression vector. These data indicate that ligand-activated PR stimulates GdA gene expression mediated through the fun ctional Spl sites. (C) 2001 Elsevier Science Ireland Ltd. All rights reserv ed.