Tissue-Specific Expression and Steroid Hormone Regulation of Human Gonadotropin -Releasing Hormone (hGnRH) Gene in Placental Cells (JEG -3 cells)
Using JEG-3 cells as an in vitro model, I investigated the mechanisms behind the tissue-specific expression and steroid hormone regulation of the hGnRH gene in the human placenta. The hGnRH upstream promoter was found to be functionally active in JEG-3 cells. The DNA sequence responsible for functioning of the upstream promoter in JEG-3 cells is narrowed to a region between –1048 bp and –730 bp. This DNA fragment contains four elements, which can bind with nuclear extract from JEG-3 cells (but not from GT1-7 cells). Estradiol (E2) represses the hGnRH upstream promoter activity in JEG-3 cells. This inhibition is receptor-mediated, dose-dependent and promoter-specific. The DNA sequence between –1048 bp and –730 bp is essential for the response of the promoter to E2. This specific DNA sequence consists of a region (–824/–784 bp) bound to nuclear extract from E2-treated JEG-3 cells. The involvement of ER in the protein-DNA interaction was not displayed. In contrast, progesterone (P4) enhances the hGnRH upstream promoter activity in the same ways as E2. The DNA sequence important for the response of the promoter to P4 is in a region between –1355 and –1048 bp. The P4 effect on the hGnRH upstream promoter can be modified by E2. In summary, this study showed that the hGnRH upstream promoter is functionally active in the placental-derived JEG-3 cells. Steroid hormones are engaged in modulating the hGnRH upstream promoter in JEG-3 cells in a receptor-mediated, dose-dependent, and promoter-specific fashion. Several cis-regulatory elements, which are responsible for the expression and regulation of the gene in JEG-3 cells, have been identified in the hGnRH upstream promoter region.
Gonadotropin-releasing hormone, JEG-3 cells, Placental cells, Steroid hormone, Cell Biology, Molecular Biology
Networked Digital Library of Theses and Dissertations