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

The mechanisms whereby progesterone (P-4), 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 (PRWT), we found that P-4 significantly inhibited IL-1 induction of the NF-B target genes, COX-2 and IL-8. P-4-PRWT 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 (PRmDBD), P-4-mediated transrepression was significantly reduced, suggesting a critical role of the PR DBD. ChIP analysis of hTERT-HM cells stably expressing PRWT or PRmDBD revealed that P-4 treatment caused equivalent recruitment of PRWT and PRmDBD 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 PRWT but poorly with PRmDBD. P-4 treatment of PRWT hTERT-HM cells caused enhanced recruitment of endogenous GATAD2B to COX-2 and IL-8 promoters. Further, siRNA knockdown of endogenous GATAD2B significantly reduced P-4-PRWT 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 P-4-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.