Department of Biochemistry and Molecular Biology, Center for Epigenetics, Genetics Institute, UF Health Cancer Center, Powell-Gene Therapy Center, Gainesville, FL 32610, USA.
Department of Molecular Genetics and Microbiology, Gainesville, FL 32610, USA.
Nucleic Acids Res. 2021 Feb 22;49(3):1383-1396. doi: 10.1093/nar/gkab002.
Super-enhancers (SEs) mediate high transcription levels of target genes. Previous studies have shown that SEs recruit transcription complexes and generate enhancer RNAs (eRNAs). We characterized transcription at the human and murine β-globin locus control region (LCR) SE. We found that the human LCR is capable of recruiting transcription complexes independently from linked globin genes in transgenic mice. Furthermore, LCR hypersensitive site 2 (HS2) initiates the formation of bidirectional transcripts in transgenic mice and in the endogenous β-globin gene locus in murine erythroleukemia (MEL) cells. HS2 3'eRNA is relatively unstable and remains in close proximity to the globin gene locus. Reducing the abundance of HS2 3'eRNA leads to a reduction in β-globin gene transcription and compromises RNA polymerase II (Pol II) recruitment at the promoter. The Integrator complex has been shown to terminate eRNA transcription. We demonstrate that Integrator interacts downstream of LCR HS2. Inducible ablation of Integrator function in MEL or differentiating primary human CD34+ cells causes a decrease in expression of the adult β-globin gene and accumulation of Pol II and eRNA at the LCR. The data suggest that transcription complexes are assembled at the LCR and transferred to the globin genes by mechanisms that involve Integrator mediated release of Pol II and eRNA from the LCR.
超级增强子 (SEs) 介导靶基因的高转录水平。先前的研究表明，SE 招募转录复合物并产生增强子 RNA (eRNA)。我们对人类和鼠β-珠蛋白基因调控区 (LCR) SE 的转录进行了表征。我们发现，人类 LCR 能够在转基因小鼠中独立于连接的珠蛋白基因招募转录复合物。此外，LCR 高敏感位点 2 (HS2) 在转基因小鼠和内源性β-珠蛋白基因座中启动双向转录的形成在小鼠红白血病 (MEL) 细胞中。HS2 3' eRNA 相对不稳定，并保持与珠蛋白基因座的密切接近。减少 HS2 3' eRNA 的丰度会导致β-珠蛋白基因转录减少，并损害启动子处的 RNA 聚合酶 II (Pol II) 募集。已经表明整合酶复合物终止 eRNA 转录。我们证明 Integrator 与 LCR HS2 下游相互作用。在 MEL 或分化的原代人 CD34+细胞中诱导 Integrator 功能缺失会导致成人β-珠蛋白基因表达减少，Pol II 和 eRNA 在 LCR 处积累。数据表明，转录复合物在 LCR 处组装，并通过涉及 Integrator 介导的 Pol II 和 eRNA 从 LCR 释放的机制转移到珠蛋白基因。
