Section of Molecular Biology, University of California, San Diego, La Jolla, CA, USA.
Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA, USA.
Nat Struct Mol Biol. 2018 Aug;25(8):687-697. doi: 10.1038/s41594-018-0102-0. Epub 2018 Aug 3.
The bromodomain and extra-terminal motif (BET) protein BRD4 binds to acetylated histones at enhancers and promoters via its bromodomains (BDs) to regulate transcriptional elongation. In human colorectal cancer cells, we found that BRD4 was recruited to enhancers that were co-occupied by mutant p53 and supported the synthesis of enhancer-directed transcripts (eRNAs) in response to chronic immune signaling. BRD4 selectively associated with eRNAs that were produced from BRD4-bound enhancers. Using biochemical and biophysical methods, we found that BRD4 BDs function cooperatively as docking sites for eRNAs and that the BDs of BRD2, BRD3, BRDT, BRG1, and BRD7 directly interact with eRNAs. BRD4-eRNA interactions increased BRD4 binding to acetylated histones in vitro and augmented BRD4 enhancer recruitment and transcriptional cofactor activities. Our results suggest a mechanism by which eRNAs are directly involved in gene regulation by modulating enhancer interactions and transcriptional functions of BRD4.
溴结构域和末端结构域（BET）蛋白 BRD4 通过其溴结构域（BD）与乙酰化组蛋白结合在增强子和启动子上，以调节转录延伸。在人结直肠癌细胞中，我们发现 BRD4 被招募到突变型 p53 共同占据的增强子上，并响应慢性免疫信号支持增强子指导的转录本（eRNA）的合成。BRD4 选择性地与从 BRD4 结合的增强子产生的 eRNA 结合。通过生化和生物物理方法，我们发现 BRD4 BD 作为 eRNA 的对接位点协同作用，并且 BRD2、BRD3、BRDT、BRG1 和 BRD7 的 BD 直接与 eRNA 相互作用。BRD4-eRNA 相互作用增加了 BRD4 与体外乙酰化组蛋白的结合，并增强了 BRD4 增强子募集和转录共因子活性。我们的结果表明，eRNA 通过调节增强子相互作用和 BRD4 的转录功能直接参与基因调控的一种机制。
