251. Functional association of PR and CCAAT/enhancer-binding protein beta isoforms: promoter-dependent cooperation between PR-B and liver-enriched inhibitory protein, or liver-enriched activatory protein and PR-A in human endometrial stromal cells
- Author
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Birgit Gellersen, Jan J. Brosens, Rita Kempf, Mark Christian, and Yvonne Pohnke
- Subjects
Gene isoform ,Transcriptional Activation ,Transcription, Genetic ,Response element ,Molecular Sequence Data ,Biology ,Response Elements ,Endometrium ,Endocrinology ,Enhancer binding ,Humans ,Protein Isoforms ,Binding site ,Promoter Regions, Genetic ,Molecular Biology ,Transcription factor ,Cells, Cultured ,Binding Sites ,Base Sequence ,Activator (genetics) ,CCAAT-Enhancer-Binding Protein-beta ,Decidualization ,Promoter ,General Medicine ,Molecular biology ,Prolactin ,Mutation ,Female ,Stromal Cells - Abstract
Activation of the decidual PRL (dPRL) promoter, a major differentiation marker in human endometrial stromal (ES) cells, by cAMP is effected through the induction and binding of CCAAT/enhancer-binding protein-beta (C/EBPbeta) to two overlapping cognate response elements in the promoter region dPRL-332/-270. Progesterone is essential for decidualization and potently enhances cAMP-dependent dPRL promoter activity. We now demonstrate that both liganded PR isoforms, PR-A and PR-B, are capable of trans-activating the dPRL-332/-270 region. The absence of a palindromic progesterone response element (PRE) within this promoter region suggested cross-coupling between C/EBPbeta and PR in human ES cells. Physical interaction between these distinct transcription factors was confirmed by glutathione-S-transferase pull-down assays, demonstrating that both C/EBPbeta isoforms, the full-length activator liver-enriched activatory protein (LAP) and the truncated inhibitor liver-enriched inhibitory protein (LIP), can bind PR-B as well as PR-A in vitro. Transient transfection studies in primary ES cells were used to examine the consequences of PR and C/EBPbeta interaction on activation of their respective response elements. Activation of mouse mammary tumor virus promoter or a reporter construct containing two isolated palindromic PREs by liganded PR-B was synergistically enhanced by coexpression of LIP, but not LAP. In contrast, PR-A failed to trans-activate these constructs significantly regardless of the presence of either C/EBPbeta isoform. Conversely, LAP-dependent activation of the dPRL-332/-270 region or a reporter construct driven by a single C/EBPbeta response element was greatly enhanced by PR-A, but not PR-B, in a ligand-dependent manner. These observations reveal that PR and C/EBPbeta isoform ratios are important determinants of the cellular response to ovarian progesterone in the reproductive tract; the predominance of PR-A and LAP favors expression of C/EBPbeta-dependent genes, whereas PR-B and LIP cooperate in activating PRE-driven promoters.
- Published
- 2002