Center for Neurobiology and Vaccine Development, Ophthalmology Research, Department of Surgery, Cedars-Sinai Burns & Allen Research Institute, CSMC-SSB3, Los Angeles, California, USA.
J Virol. 2022 Feb 9;96(3):e0198521. doi: 10.1128/JVI.01985-21. Epub 2021 Dec 1.
Herpes simplex virus 1 (HSV-1) latency-associated transcript (LAT) plays a significant role in efficient establishment of latency and reactivation. LAT has antiapoptotic activity and downregulates expression of components of the type I interferon pathway. LAT also specifically activates expression of the herpesvirus entry mediator (HVEM), one of seven known receptors used by HSV-1 for cell entry that is crucial for latency and reactivation. However, the mechanism by which LAT regulates HVEM expression is not known. LAT has two small noncoding RNAs (sncRNAs) that are not microRNAs (miRNAs), within its 1.5-kb stable transcript, which also have antiapoptotic activity. These sncRNAs may encode short peptides, but experimental evidence is lacking. Here, we demonstrate that these two sncRNAs control HVEM expression by activating its promoter. Both sncRNAs are required for wild-type (WT) levels of activation of HVEM, and sncRNA1 is more important in HVEM activation than sncRNA2. Disruption of a putative start codon in sncRNA1 and sncRNA2 sequences reduced HVEM promoter activity, suggesting that sncRNAs encode a protein. However, we did not detect peptide binding using two chromatin immunoprecipitation (ChIP) approaches, and a web-based algorithm predicts low probability that the putative peptides bind to DNA. In addition, computational modeling predicts that sncRNA molecules bind with high affinity to the HVEM promoter, and deletion of these binding sites to sncRNA1, sncRNA2, or both reduced HVEM promoter activity. Together, our data suggest that sncRNAs exert their function as RNA molecules, not as proteins, and we provide a model for the predicted binding affinities and binding sites of sncRNA1 and sncRNA2 in the HVEM promoter. HSV-1 causes recurrent ocular infections, which is the leading cause of corneal scarring and blindness. Corneal scarring is caused by the host immune response to repeated reactivation events. LAT functions by regulating latency and reactivation, in part by inhibiting apoptosis and activating HVEM expression. However, the mechanism used by LAT to control HVEM expression is unclear. Here, we demonstrate that two sncRNAs within the 1.5-kb LAT transcript activate HVEM expression by binding to two regions of its promoter. Interfering with these interactions may reduce latency and thereby eye disease associated with reactivation.
单纯疱疹病毒 1(HSV-1)潜伏相关转录物(LAT)在有效建立潜伏和再激活方面发挥重要作用。LAT 具有抗凋亡活性,并下调 I 型干扰素途径成分的表达。LAT 还特异性激活疱疹病毒进入介质(HVEM)的表达,HVEM 是 HSV-1 用于细胞进入的七个已知受体之一,对潜伏和再激活至关重要。然而,LAT 调节 HVEM 表达的机制尚不清楚。LAT 在其 1.5kb 稳定转录物内有两个非编码小 RNA(sncRNA),它们不是 microRNAs(miRNAs),也具有抗凋亡活性。这些 sncRNA 可能编码短肽,但缺乏实验证据。在这里,我们证明这两个 sncRNA 通过激活其启动子来控制 HVEM 的表达。这两个 sncRNA 都需要野生型(WT)水平的 HVEM 激活,sncRNA1 在 HVEM 激活中比 sncRNA2 更重要。破坏 sncRNA1 和 sncRNA2 序列中的推定起始密码子降低了 HVEM 启动子活性,表明 sncRNA 编码一种蛋白质。然而,我们没有使用两种染色质免疫沉淀(ChIP)方法检测到肽结合,并且基于网络的算法预测假定的肽与 DNA 结合的可能性较低。此外,计算建模预测 sncRNA 分子与 HVEM 启动子具有高亲和力结合,并且 sncRNA1、sncRNA2 或两者的这些结合位点的缺失降低了 HVEM 启动子活性。总之,我们的数据表明 sncRNA 作为 RNA 分子而不是蛋白质发挥其功能,并且我们提供了 sncRNA1 和 sncRNA2 在 HVEM 启动子中的预测结合亲和力和结合位点的模型。HSV-1 引起复发性眼部感染,这是角膜瘢痕和失明的主要原因。角膜瘢痕是由宿主对反复再激活事件的免疫反应引起的。LAT 通过调节潜伏和再激活起作用,部分通过抑制细胞凋亡和激活 HVEM 表达。然而,LAT 控制 HVEM 表达的机制尚不清楚。在这里,我们证明 LAT 转录物内的两个 sncRNA 通过与启动子的两个区域结合来激活 HVEM 的表达。干扰这些相互作用可能会降低潜伏率,从而减少与再激活相关的眼部疾病。