Counteracting effects of cellular Notch and Epstein-Barr virus EBNA2: implications for stromal effects on virus-host interactions.
Counteracting effects of cellular Notch and Epstein-Barr virus EBNA2: implications for stromal effects on virus-host interactions.
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DOI：
10.1128/jvi.01431-14
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发表时间：
2014-10
影响因子：
5.4
通讯作者：
Shannon-Lowe C
中科院分区：
文献类型：
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作者：
Rowe M;Raithatha S;Shannon-Lowe C
许多不同的环境信号与B淋巴细胞的分化和激活有关。其中一个信号，Notch-2，可能与EB病毒(EBV)感染的生物学特别相关，EBV定植于B细胞室。激活的Notch和EB病毒核抗原2(EBNA2)都是通过与转录因子RBP-Jκ相互作用而发挥转录激活作用的。尽管EBNA2和激活的Notch似乎具有部分重叠的功能，但我们现在报告，激活的Notch在新感染的原代B细胞和淋巴母细胞系(LCLS)中都抵消了关键的EBNA2功能。EBNA2直接负责启动大多数与III型潜伏期相关的EBV蛋白的转录，导致LCLS的生长。驱动这种生长的关键蛋白质之一是潜伏膜蛋白1(LMP1)，它由ED-L1启动子中的EBNA2反应元件调控。通过Delta样配体1激活Notch-2可抑制EBNA2介导的LMP1转录启动。此外，连接的Notch-2还有效地关闭了已经表达LMP1的LCLS中ED-L1启动子的LMP1表达。Notch对EBV基因表达的调节并不局限于EBNA2依赖事件。激活的Notch-2还通过上调细胞转录因子ZEB2，抑制BZLF1的转录，从而抑制EBV进入B细胞非霍奇金淋巴瘤的裂解周期。这些结果支持这样的概念，即在体内，来自微环境的累积信号将B细胞中EBV基因的表达下调至进入外周血的B细胞中观察到的潜伏期0基因表达谱。EB病毒实验感染静息B细胞导致病毒基因表达的生长转化程序和淋巴母细胞系的生长。以前在单细胞水平上的研究揭示了复杂的细胞和病毒信号网络调节病毒基因组的转录。这项研究表明，淋巴组织微环境中基质细胞上表达的分子也可以从根本上改变病毒基因的表达，特别是基质细胞上的Delta样配体1连接受感染的B细胞上的Notch-2。Notch的激活干扰了EBNA2的反式激活功能，下调了LMP1和LMP2a的表达，并通过阻止BZLF1的表达来抑制B细胞非霍奇金淋巴瘤细胞系中溶血性病毒的复制。这些观察的意义在于，它们表明了正常淋巴组织中的微环境可能有助于抑制病毒基因表达的新机制，从而能够在记忆B细胞中建立真正的潜伏期。
A number of diverse environmental cues have been linked to B lymphocyte differentiation and activation. One such cue, Notch-2, may be particularly relevant to the biology of infection with Epstein-Barr virus (EBV), which colonizes the B cell compartment. Activated Notch and EBV nuclear antigen 2 (EBNA2) both function as transcriptional activators by virtue of their interactions with the transcription factor RBP-Jκ. Although EBNA2 and activated Notch appear to have partially overlapping functions, we now report that activated Notch counteracts a crucial EBNA2 function both in newly infected primary B cells and in lymphoblastoid cell lines (LCLs). EBNA2 is directly responsible for the initiation of transcription of the majority of EBV proteins associated with type III latency, leading to the outgrowth of LCLs. One of the key proteins driving this outgrowth is latent membrane protein 1 (LMP1), which is regulated by an EBNA2-responsive element within its ED-L1 promoter. Activation of Notch-2 via Delta-like ligand 1 inhibits EBNA2-mediated initiation of LMP1 transcription. Furthermore, ligated Notch-2 also efficiently turns off LMP1 expression from the ED-L1 promoter in LCLs already expressing LMP1. Modulation of EBV gene expression by Notch was not confined to EBNA2-dependent events. Activated Notch-2 also inhibited EBV entry into the lytic cycle in a B cell non-Hodgkin's lymphoma line by upregulating the cellular transcription factor Zeb2, which represses the transcription of BZLF1. These results support the concept that in vivo, cumulative signals from the microenvironment downregulate EBV gene expression in B cells to the latency 0 gene expression profile observed in B cells entering the peripheral blood. IMPORTANCE Experimental infection of resting B cells by Epstein-Barr virus leads to the growth transformation program of virus gene expression and the outgrowth of lymphoblastoid cell lines. Previous studies at the single-cell level revealed complex cellular and viral signaling networks regulating transcription of the viral genome. This study demonstrates that viral gene expression can also be radically altered by molecules expressed on stromal cells in the microenvironment of lymphoid tissue, specifically, Delta-like ligand 1 on stromal cells ligating Notch-2 on infected B cells. Activation of Notch interferes with the transactivation function of EBNA2, downregulates the expression of LMP1 and LMP2a, and inhibits the activation of lytic virus replication in a B cell non-Hodgkin's lymphoma line by preventing expression of BZLF1. The significance of these observations is that they indicate new mechanisms whereby the microenvironment in normal lymphoid tissue may facilitate the repression of viral gene expression, enabling establishment of true latency in memory B cells.