The transcriptional repressor GATAD2B mediates progesterone receptor suppression of myometrial contractile gene expression

The mechanisms whereby progesterone (P₄), acting via the progesterone receptor (PR), inhibits proinflammatory/contractile gene expression during pregnancy are incompletely defined. Using immortalized human myometrial (hTERT-HM) cells stably expressing wild-type PR-A or PR-B (PR_WT), we found that P₄ significantly inhibited IL-1 induction of the NF-B target genes, COX-2 and IL-8. P₄–PR_WT transrepression occurred at the level of transcription initiation and was mediated by decreased recruitment of NF-B p65 and RNA polymerase II to COX-2 and IL-8 promoters. However, in cells stably expressing a PR-A or PR-B DNA-binding domain mutant (PR_mDBD), P₄-mediated transrepression was significantly reduced, suggesting a critical role of the PR DBD. ChIP analysis of hTERT-HM cells stably expressing PR_WT or PR_mDBD revealed that P₄ treatment caused equivalent recruitment of PR_WT and PR_mDBD to COX-2 and IL-8 promoters, suggesting that PR inhibitory effects were not mediated by its direct DNA binding. Using immunoprecipitation, followed by MS, we identified a transcriptional repressor, GATA zinc finger domain–containing 2B (GATAD2B), that interacted strongly with PR_WT but poorly with PR_mDBD. P₄ treatment of PR_WT hTERT-HM cells caused enhanced recruitment of endogenous GATAD2B to COX-2 and IL-8 promoters. Further, siRNA knockdown of endogenous GATAD2B significantly reduced P₄–PR_WT transrepression of COX-2 and IL-8. Notably, GATAD2B expression was significantly decreased in pregnant mouse and human myometrium during labor. Our findings suggest that GATAD2B serves as an important mediator of P₄–PR suppression of proinflammatory and contractile genes during pregnancy. Decreased GATAD2B expression near term may contribute to the decline in PR function, leading to labor.