Bromodomain-containing Protein 4 (BRD4) is Required for the Maintenance of a Mammary Epithelial Phenotype [RNA-Seq]

Bromodomain-containing protein 4 (BRD4) is an important epigenetic reader which promotes gene transcription to modulate cell-specific functions and is under intensive investigation for its potential as an anti-tumor therapeutic target. However, the role of BRD4 in non-transformed cells remains unclear. Here we demonstrate that BRD4 is required for the expression of epithelial-specific genes and suppression of stem cell-like properties by binding to the distal regions of epithelial-related genes. Moreover, BRD4 occupancy correlates with enhancer activity and enhancer RNA (eRNA) transcription of epithelial differentiation-specific genes. Interestingly, we show that BRD4 perturbation regulates the expression of Grainy Head-like transcription factor, GRHL3, whose depletion partially mimics BRD4 inhibition and blocks differentiated phenotype. By binding to the distal regions of GRHL3, BRD4 promotes RNA polymerase-II occupancy and thus affects eRNA transcription. Altogether, these findings provide evidence that BRD4 promotes a differentiated epithelial phenotype in non-transformed mammary cells at least in part through the activation of GRHL3 expression. Overall design: mRNA expression profiles of MCF10A cells under negative control siRNA, BRD4 siRNA or JQ1 treatment, in duplicates.

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Nagarajan S, Bedi U, Budida A, Hamdan FH, Mishra VK, Najafova Z, Xie W, Alawi M, Indenbirken D, Knapp S, Chiang CM, Grundhoff A, Kari V, Scheel CH, Wegwitz F, Johnsen SA