Histone deacetylase inhibition and progesterone act synergistically to stimulate baboon glycodelin gene expression.

During the late luteal phase of the menstrual cycle and early pregnancy, the major secretory product of the uterine glandular epithelial cells in humans and non-human primates is glycodelin. Previous studies using Ishikawa cells, a human endometrial cell line, have shown that a chimeric plasmid containing the baboon glycodelin promoter responds to progestins but the response is modest compared with the induction of glycodelin seen in vivo and in gene array analysis. A recent report indicating that the histone deacetylase inhibitor trichostatin A (TSA) promoted glycodelin expression prompted us to examine its mechanism of action. In Ishikawa cells transfected with the baboon glycodelin promoter, TSA and the synthetic progestin medroxyprogesterone acetate both stimulated expression of the reporter and the combined treatment produced a synergistic effect. The effect of TSA and progestin was absent when the same promoter constructs were transfected into COS-1 cells, a kidney cell line, and a TSA effect but no progestin effect was observed in T47D cells, a mammary cell line. Through deletion analysis, the TSA action was localized to the -67/-52 region of the baboon glycodelin promoter, a region which contains the proximal Sp1 site. Deletions of this same region had no effect on progestin responsiveness. Our findings indicate that at least two regions of the glycodelin promoter are important for the normal induction of glycodelin expression. Non-target cells may lack factors which act on the response elements resulting in the restriction of expression to the appropriate target tissue.

Mitogen-activated protein kinase is involved in the progesterone-mediated induction of baboon glycodelin.

In the human and non-human primate the major secretory product of the uterine glandular epithelial cells is glycodelin. The expression of glycodelin is associated with elevated progesterone levels as its production peaks during the late luteal phase of the menstrual cycle and in early pregnancy. Consistent with our previous studies, we found that the majority of the progestin responsiveness of the baboon glycodelin promoter was retained in the -20+48 region, a region devoid of progestin- and Sp1-response elements. Using serial 5' and 3' deletions of 10 basepairs of the promoter within the pGL3Basic vector, we identified the 5' and 3' limits required for progestin responsiveness as -22 and +18, respectively. When the same regions were cloned into the pGL3Promoter vector, a construct that contains the heterologous SV40 promoter, progestin did not enhance expression. Mutation of the DNA binding domain of the progesterone receptor, which disrupts its ability to activate the progesterone response element, does not obliterate its ability to induce expression via the baboon glycodelin promoter. Inhibitors of protein tyrosine kinases, genistein and AG18, blocked the progestin-mediated induction as did an inhibitor of MEK, PD98059, but not an inhibitor of p38 MAP kinase, SB202190. These findings imply that glycodelin induction in response to progestins involves a nongenomic mechanism through the ERK1/2 branch of the MAP kinase pathway. The ultimate target may be a factor involved in the initiation of glycodelin gene transcription.