Engdahl Elin, Dunn Nicky, Niehusmann Pitt, Wideman Sarah, Wipfler Peter, Becker Albert J, Ekström Tomas J, Almgren Malin, Fogdell-Hahn Anna
Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, and Center for Molecular Medicine, Stockholm, Sweden.
Department of Neurology/Pathology, Oslo University Hospital, Oslo, Norway.
J Virol. 2017 May 12;91(11). doi: 10.1128/JVI.02105-16. Print 2017 Jun 1.
Human herpesvirus 6B (HHV-6B) is a neurotropic betaherpesvirus that achieves latency by integrating its genome into host cell chromosomes. Several viruses can induce epigenetic modifications in their host cells, but no study has investigated the epigenetic modifications induced by HHV-6B. This study analyzed methylation with an Illumina 450K array, comparing HHV-6B-infected and uninfected Molt-3 T cells 3 days postinfection. Bisulfite pyrosequencing was used to validate the Illumina results and to investigate methylation over time Expression of genes was investigated using quantitative PCR (qPCR), and virus integration was investigated with PCR. A total of 406 CpG sites showed a significant HHV-6B-induced change in methylation Remarkably, 86% (351/406) of these CpGs were located <1 Mb from chromosomal ends and were all hypomethylated in virus-infected cells. This was most evident at chromosome 17p13.3, where HHV-6B had induced CpG hypomethylation after 2 days of infection, possibly through TET2, which was found to be upregulated by the virus. In addition, virus-induced cytosine hydroxymethylation was observed. Genes located in the hypomethylated region at 17p13.3 showed significantly upregulated expression in HHV-6B-infected cells. A temporal experiment revealed HHV-6B integration in Molt-3 cell DNA 3 days after infection. The telomere at 17p has repeatedly been described as an integration site for HHV-6B, and we show for the first time that HHV-6B induces hypomethylation in this region during acute infection, which may play a role in the integration process, possibly by making the DNA more accessible. The ability to establish latency in the host is a hallmark of herpesviruses, but the mechanisms differ. Human herpesvirus 6B (HHV-6B) is known to establish latency through integration of its genome into the telomeric regions of host cells, with the ability to reactivate. Our study is the first to show that HHV-6B specifically induces hypomethylated regions close to the telomeres and that integrating viruses may use the host methylation machinery to facilitate their integration process. The results from this study contribute to knowledge of HHV-6B biology and virus-host interaction. This in turn will lead to further progress in our understanding of the underlying mechanisms by which HHV-6B contributes to pathological processes and may have important implications in both disease prevention and treatment.
人疱疹病毒6B(HHV - 6B)是一种嗜神经β疱疹病毒,通过将其基因组整合到宿主细胞染色体中来实现潜伏感染。几种病毒可在其宿主细胞中诱导表观遗传修饰,但尚无研究调查HHV - 6B诱导的表观遗传修饰。本研究使用Illumina 450K芯片分析甲基化情况,比较感染HHV - 6B和未感染的Molt - 3 T细胞在感染后3天的情况。亚硫酸氢盐焦磷酸测序用于验证Illumina结果并研究随时间的甲基化变化。使用定量PCR(qPCR)研究基因表达,并通过PCR研究病毒整合情况。共有406个CpG位点显示出HHV - 6B诱导的甲基化显著变化。值得注意的是,这些CpG位点中有86%(351/406)位于距染色体末端<1 Mb处,且在病毒感染细胞中均为低甲基化。这在染色体17p13.3处最为明显,在感染2天后HHV - 6B诱导了CpG低甲基化,可能是通过TET2,发现该基因被病毒上调。此外,还观察到病毒诱导的胞嘧啶羟甲基化。位于17p13.3低甲基化区域的基因在HHV - 6B感染细胞中表达显著上调。一项时间实验显示感染后3天HHV - 6B整合到Molt - 3细胞DNA中。17p处的端粒多次被描述为HHV - 6B的整合位点,我们首次表明HHV - 6B在急性感染期间在该区域诱导低甲基化,这可能在整合过程中起作用,可能是通过使DNA更容易接近。在宿主体内建立潜伏感染的能力是疱疹病毒的一个标志,但机制有所不同。已知人疱疹病毒6B(HHV - 6B)通过将其基因组整合到宿主细胞的端粒区域来建立潜伏感染,并具有重新激活的能力。我们的研究首次表明HHV - 6B特异性诱导靠近端粒的低甲基化区域,并且整合病毒可能利用宿主甲基化机制来促进其整合过程。本研究结果有助于了解HHV - 6B生物学和病毒 - 宿主相互作用。这反过来将导致我们在理解HHV - 6B促成病理过程的潜在机制方面取得进一步进展,并可能在疾病预防和治疗中具有重要意义。