Nanog Requires BRD4 to Maintain Murine Embryonic Stem Cell Pluripotency and Is Suppressed by Bromodomain Inhibitor JQ1 Together with Lefty1

Abstract

Embryonic stem cells (ESCs) are maintained in an undifferentiated state through expression of the core transcriptional factors Nanog, Oct4, and Sox2. However, the epigenetic regulation of pluripotency is poorly understood. Differentiation of ESCs is accompanied by a global reduction of panacetylation of histones H3 and H4 suggesting that histone acetylation plays an important role in maintenance of ESC pluripotency. Acetylated lysine residues on histones are read by members of the bromodomain family that includes BET (bromodomain and extraterminal domain) proteins for which highly potent and selective inhibitors have been developed. In this study we demonstrate that the pan-BET bromodomain inhibitor JQ1 induces rapid spontaneous differentiation of murine ESCs by inducing marked transcriptional downregulation of Nanog as well as the stemness markers Lefty1 and Lefty2, but not Myc, often used as a marker of BET inhibitor activity in cancer. We show that the effects of JQ1 are recapitulated by knockdown of the BET family member BRD4 implicating this protein in Nanog regulation. These data are also supported by chromatin immunoprecipitation experiments which confirm BRD4 binding at the Nanog promoter that is known to require acetylation by the histone acetyltransferase MOF for transcriptional activity. In further support of our findings, we show that JQ1 antagonizes the stem cellpromoting effects of the histone deacetylase inhibitors sodium butyrate and valproic acid. Our data suggest that BRD4 is critical for the maintenance of ESC pluripotency and that this occurs primarily through the maintenance of Nanog expression.

The bromodomain inhibitor OTX015 (MK-8628) exerts anti-tumor activity in triple-negative breast cancer models as single agent and in combination with everolimus

“…It has been suggested that the failure of cytotoxic chemotherapeutics such as taxanes and cisplatin in TNBC patients and ovarian cancer-derived cells may be due to the induction of CSC generation [41, 42]. As shown herein, OTX015 down-regulated the expression of genes specifically associated with stemness processes such as NANOG and OCT4 , both in vitro and in vivo .…”

HPV16-E2 protein modifies self-renewal and differentiation rate in progenitor cells of human immortalized keratinocytes

“…The modification in the expression level of these stemness factors could be related to the ability of HPV16-E2 protein to physically interact with several transcription factors such as CBP/p300, SP1, TAF1 and BRD4 [33, 65–68], all of them involved in the regulation of crucial genes for proliferation and differentiation pathways, and also in the regulation of SOX2 , NANOG and OCT4 expression [56, 61]. As an example, it has been demonstrated that BRD4 is a very important piece in the regulation of NANOG gene expression [68], and the well known capability of HPV16-E2 to stabilize the binding of BRD4 to cellular promoters [69] could explain the overexpression observed in cells where HPV16-E2 is present.…”

“…As an example, it has been demonstrated that BRD4 is a very important piece in the regulation of NANOG gene expression [68], and the well known capability of HPV16-E2 to stabilize the binding of BRD4 to cellular promoters [69] could explain the overexpression observed in cells where HPV16-E2 is present. On the other side, it has been reported that SP1 factor binds directly to the OCT4 promoter favoring its transcription [70].…”

BRD4 is associated with raccoon polyomavirus genome and mediates viral gene transcription and maintenance of a stem cell state in neuroglial tumour cells

“…BRD4 is also involved in DNA viral gene transcription and viral genome replication in papillomaviruses and Merkel cell polyomavirus (McBride & Jang, 2013;Ottinger et al, 2006;Wang et al, 2012). Recent work has also demonstrated a role for BRD4 in the maintenance of a pluripotent stem cell state, and in repressing differentiation in stem cells (Horne et al, 2015;Wu et al, 2015). Given this intersection, we investigated whether expression of BRD4 could account for the maintenance of RacPyV in neural stem cells and continued expression of oncogenic viral genes.…”