Enhancer Control of MicroRNA miR-155 Expression in Epstein-Barr Virus-Infected B Cells.
Enhancer Control of MicroRNA miR-155 Expression in Epstein-Barr Virus-Infected B Cells.
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DOI：
10.1128/jvi.00716-18
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发表时间：
2018-10-01
影响因子：
5.4
通讯作者：
West MJ
中科院分区：
文献类型：
--
作者：
Wood CD;Carvell T;Gunnell A;Ojeniyi OO;Osborne C;West MJ
microRNA miR-155在许多人类癌症中以高水平表达，特别是淋巴瘤。EB病毒（EBV）感染人类B细胞并驱动许多淋巴瘤的发展。EBV携带的两个基因（LMP 1和EBNA 2）上调miR-155表达，并且miR-155表达是EBV感染的B细胞生长所需的。我们发现EBV转录因子EBNA 2通过激活miR-155宿主基因（miR-155 HG）上游的增强子上调miR-155表达，miR-155来源于该宿主基因。我们表明EBNA 2还通过增强子介导的IRF 4激活间接激活miR-155表达。然后，IRF 4独立于EBNA 2激活miR-155 HG启动子和上游增强子。去除miR-155 HG增强子的基因编辑导致miR-155 HG表达减少。因此，我们确定增强子介导的miR-155 HG激活是促进B细胞生长的关键步骤，也是淋巴瘤发展的可能贡献者。致癌microRNA（miRNA）miR-155是EB病毒（EBV）阳性B细胞恶性肿瘤中最常上调的miRNA，并且在其他非病毒性淋巴瘤中上调。已知EBV核抗原2（EBNA 2）和B细胞转录因子干扰素调节因子4（IRF 4）都激活加工miR-155的宿主细胞基因（miR-155 HG; BIC）的转录。EBNA 2还激活IRF 4转录，表明EBV可能通过直接和间接机制上调miR-155。然而，EBNA 2对IRF 4和miR-155 HG的转录调控机制尚未确定。我们证明EBNA 2可以通过特定的上游增强子激活IRF 4和miR-155 HG的表达，这些增强子依赖于Notch信号传导转录因子RBPJ，RBPJ是EBNA 2的已知结合伴侣。我们证明，除了激活miR-155 HG启动子外，IRF 4还可以通过EBNA 2靶向的上游增强子激活miR-155 HG。基因编辑去除位于miR-155 HG上游60 kb的EBNA 2和IRF 4响应性miR-155 HG增强子导致EBV感染细胞中miR-155 HG表达减少。因此，我们的数据表明，特异性RBPJ依赖性增强子调节IRF 4-miR-155表达网络，并在EBV感染的B细胞中维持miR-155表达中发挥关键作用。这些发现提供了重要的见解，将提高我们对B细胞恶性肿瘤中miR-155控制的理解。重要性MicroRNA miR-155在许多人类癌症中高水平表达，特别是淋巴瘤。EB病毒（EBV）感染人类B细胞并驱动许多淋巴瘤的发展。EBV携带的两个基因（LMP 1和EBNA 2）上调miR-155表达，并且miR-155表达是EBV感染的B细胞生长所需的。我们发现EBV转录因子EBNA 2通过激活miR-155宿主基因（miR-155 HG）上游的增强子上调miR-155表达，miR-155来源于该宿主基因。我们表明EBNA 2还通过增强子介导的IRF 4激活间接激活miR-155表达。然后，IRF 4独立于EBNA 2激活miR-155 HG启动子和上游增强子。去除miR-155 HG增强子的基因编辑导致miR-155 HG表达减少。因此，我们确定增强子介导的miR-155 HG激活是促进B细胞生长的关键步骤，也是淋巴瘤发展的可能贡献者。
MicroRNA miR-155 is expressed at high levels in many human cancers, particularly lymphomas. Epstein-Barr virus (EBV) infects human B cells and drives the development of numerous lymphomas. Two genes carried by EBV (LMP1 and EBNA2) upregulate miR-155 expression, and miR-155 expression is required for the growth of EBV-infected B cells. We show that the EBV transcription factor EBNA2 upregulates miR-155 expression by activating an enhancer upstream from the miR-155 host gene (miR-155HG) from which miR-155 is derived. We show that EBNA2 also indirectly activates miR-155 expression through enhancer-mediated activation of IRF4. IRF4 then activates both the miR-155HG promoter and the upstream enhancer, independently of EBNA2. Gene editing to remove the miR-155HG enhancer leads to a reduction in miR-155HG expression. We therefore identify enhancer-mediated activation of miR-155HG as a critical step in promoting B cell growth and a likely contributor to lymphoma development. The oncogenic microRNA (miRNA) miR-155 is the most frequently upregulated miRNA in Epstein-Barr virus (EBV)-positive B cell malignancies and is upregulated in other nonviral lymphomas. Both EBV nuclear antigen 2 (EBNA2) and the B cell transcription factor interferon regulatory factor 4 (IRF4) are known to activate transcription of the host cell gene from which miR-155 is processed (miR-155HG; BIC). EBNA2 also activates IRF4 transcription, indicating that EBV may upregulate miR-155 through direct and indirect mechanisms. The mechanism of transcriptional regulation of IRF4 and miR-155HG by EBNA2, however, has not been defined. We demonstrate that EBNA2 can activate IRF4 and miR-155HG expression through specific upstream enhancers that are dependent on the Notch signaling transcription factor RBPJ, a known binding partner of EBNA2. We demonstrate that in addition to the activation of the miR-155HG promoter, IRF4 can also activate miR-155HG via the upstream enhancer also targeted by EBNA2. Gene editing to remove the EBNA2- and IRF4-responsive miR-155HG enhancer located 60 kb upstream of miR-155HG led to reduced miR-155HG expression in EBV-infected cells. Our data therefore demonstrate that specific RBPJ-dependent enhancers regulate the IRF4–miR-155 expression network and play a key role in the maintenance of miR-155 expression in EBV-infected B cells. These findings provide important insights that will improve our understanding of miR-155 control in B cell malignancies. IMPORTANCE MicroRNA miR-155 is expressed at high levels in many human cancers, particularly lymphomas. Epstein-Barr virus (EBV) infects human B cells and drives the development of numerous lymphomas. Two genes carried by EBV (LMP1 and EBNA2) upregulate miR-155 expression, and miR-155 expression is required for the growth of EBV-infected B cells. We show that the EBV transcription factor EBNA2 upregulates miR-155 expression by activating an enhancer upstream from the miR-155 host gene (miR-155HG) from which miR-155 is derived. We show that EBNA2 also indirectly activates miR-155 expression through enhancer-mediated activation of IRF4. IRF4 then activates both the miR-155HG promoter and the upstream enhancer, independently of EBNA2. Gene editing to remove the miR-155HG enhancer leads to a reduction in miR-155HG expression. We therefore identify enhancer-mediated activation of miR-155HG as a critical step in promoting B cell growth and a likely contributor to lymphoma development.