Cytokine and progesterone receptor interplay in the regulation of MUC1 gene expression.

Mucin 1 (MUC1), a transmembrane mucin expressed at the apical surface of uterine epithelia, is a barrier to microbial infection and enzymatic attack. MUC1 loss at implantation sites appears to be required to permit embryo attachment and implantation in most species. MUC1 expression is regulated by progesterone (P) and proinflammatory cytokines, including TNFα and interferon γ (IFNγ). TNFα and IFNγ are highly expressed in uterine tissues under conditions where MUC1 expression is also high and activate MUC1 expression via their downstream transcription factors, nuclear factor (NF) κB and signal transducers and activators of transcription. P receptor (PR) regulates MUC1 gene expression in a PR isoform-specific fashion. Here we demonstrate that interactions among PR isoforms and cytokine-activated transcription factors cooperatively regulate MUC1 expression in a human uterine epithelial cell line, HES. Low doses of IFNγ and TNFα synergistically stimulate MUC1 promoter activity, enhance PRB stimulation of MUC1 promoter activity and cooperate with PRA to stimulate MUC1 promoter activity. Cooperative stimulation of MUC1 promoter activity requires the DNA-binding domain of the PR isoforms. MUC1 mRNA and protein expression is increased by cytokine and P treatment in HES cells stably expressing PRB. Using chromatin immunoprecipitation assays, we demonstrate efficient recruitment of NFκB, p300, SRC3 (steroid receptor coactivator 3), and PR to the MUC1 promoter. Collectively, our studies indicate a dynamic interplay among cytokine-activated transcription factors, PR isoforms and transcriptional coregulators in modulating MUC1 expression. This interplay may have important consequences in both normal and pathological contexts, e.g. implantation failure and recurrent miscarriages.