The BET family member BRD4 interacts with OCT4 and regulates pluripotency gene expression.
Bottom Line: OCT4 directly binds Xite and Tsix, which encode two long noncoding RNAs (lncRNAs) that suppress the silencer lncRNA, Xist.Here we show that BRD4, a member of the BET protein subfamily, interacts with OCT4.BRD4 occupies the regulatory regions of pluripotent genes and the lncRNAs of XCI.
Affiliation: Burke Medical Research Institute, 785 Mamaroneck Avenue, White Plains, NY 10605, USA; Departments of Neuroscience and Cell and Developmental Biology, Weill Cornell Medical College, New York, NY 10065, USA.Show MeSH
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Mentions: We postulate that a co-activator such as BRD4 might play a role in epigenetic memory for binary cell fate (“stem-ness” versus differentiation) and XCI (active versus inactive X chromosome) status in ESCs. To explore this possibility, we examined the developmental expression pattern for the BRD4 protein in differentiating female and male ESCs. To differentiate the ESCs, we removed LIF and mouse embryonic feeders on nonadherent plates as previously described (Donohoe et al., 2007). Our results show that the BRD4 protein is expressed at similar levels during differentiation day 0 (d0) (pre-XCI), day 4 (d4) (time of the establishment of XCI), and day 8 (d8) (post-XCI) in both female and male ESCs (Figure 1A). In contrast, the OCT4 protein is present at d0 and d4 and is greatly reduced by d8 in these cells. Because the loss of mouse Brd4 has a peri-implantation phenotype (at the time random XCI takes place in the epiblast) and given the tight linkage between XCI and differentiation, we questioned whether BRD4 might interact with pluripotent factors. Using a candidate approach, we tested BRD4 for partnering with “stem-ness”-associated transcription factors. Full-length Myc-tagged BRD4 and Flag-OCT4 were co-transfected into human embryonic kidney (HEK) cells and tested for their interaction. We observed a specific OCT4-BRD4 interaction following co-immunoprecipitation (co-IP) (Figure 1B).
Affiliation: Burke Medical Research Institute, 785 Mamaroneck Avenue, White Plains, NY 10605, USA; Departments of Neuroscience and Cell and Developmental Biology, Weill Cornell Medical College, New York, NY 10065, USA.