Research ArticlePhysiology

RelB/p52-mediated NF-κB signaling alters histone acetylation to increase the abundance of corticotropin-releasing hormone in human placenta

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Sci. Signal.  25 Aug 2015:
Vol. 8, Issue 391, pp. ra85
DOI: 10.1126/scisignal.aaa9806

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Epigenetics in stress and labor

Pregnancy and labor are regulated by fluctuating hormone levels. Glucocorticoids stimulate production of the stress-responsive corticotropin-releasing hormone (CRH) in the placenta as the fetus nears full term. Using cultured primary trophoblasts isolated from midtrimester and full-term placenta, Di Stefano et al. found that glucocorticoids promote the expression of CRH by stimulating dynamic histone acetylation mediated by the binding of a complex containing the transcription factor nuclear factor κB (NF-κB), a histone lysine acetyltransferase, and a histone deacetylase to the CRH promoter. The findings reveal an epigenetic mechanism regulating the duration of pregnancy.

Abstract

Corticotropin-releasing hormone (CRH) produced in the placenta may be part of a clock that regulates the length of human gestation. Maternal plasma CRH abundance exponentially increases as pregnancy advances. Glucocorticoid stimulates CRH expression in full-term human placenta by promoting noncanonical (RelB/p52 heterodimer-mediated) nuclear factor κB (NF-κB) pathway activity. Using dexamethasone to mimic glucocorticoid exposure, we found that an epigenetic switch mediated the glucocorticoid-induced expression of CRH as gestation advances. The amount of acetylated histone H3 lysine 9 (H3K9) associated with the CRH promoter was greater in cytotrophoblasts from full-term placenta than in those from midterm placenta. Knocking down the lysine acetyltransferase CBP reduced H3K9 histone acetylation and prevented dexamethasone-induced CRH expression. Unexpectedly, knocking down the histone deacetylase HDAC1 or pharmacologically inhibiting type I and II HDACs also decreased the expression of CRH yet increased the acetylation of H3K9 and other histone regions. Both CBP and HDAC1 bound at the CRH promoter in a complex with the RelB/p52 heterodimer in a mutually dependent manner; knocking down any one factor in the complex prevented binding of the others as well as the dexamethasone-induced CRH expression. Our results suggest that glucocorticoids induce a transcription complex consisting of RelB/p52, CBP, and HDAC1 that triggers a dynamic acetylation-mediated epigenetic change to induce CRH expression in full-term human placenta.

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