Herpesvirus-Chromatin-Programmierung während der De-Novo-Infektion

在所有疱疹病毒感染中，未染色质的、表观遗传幼稚的DNA分子进入核是一个中心事件。在核传递后，病毒表型可以激活裂解基因的级联表达，导致病毒后代的产生和宿主细胞的死亡，或者获得潜在的染色质状态，介导裂解基因的选择性和可逆性沉默。潜伏的染色质允许病毒基因组保持休眠状态，直到收到重新激活的信号，而抗病毒宿主防御促进结构性抑制染色质状态，以全局抑制入侵的DNA。如果病毒未能逃脱或操纵这些防御，病毒的表观染色体就会永久沉默或清除。到目前为止，人们对成功建立潜在染色质的染色质因子和表观遗传途径还知之甚少。鉴于它们的进化关系，我们假设到目前为止尚未发现的基本原理在不同的疱疹病毒之间是相同的。为了解决这一假设，我们将在这里对两种人类疱疹病毒进行比较分析：伽玛疱疹病毒卡波西肉瘤相关疱疹病毒(KSHV)和甲型疱疹病毒水痘带状疱疹病毒(VZV)。根据我们之前的观察，我们假设这两种病毒都利用了默认的宿主途径，这些宿主途径已经进化成快速地将多梳抑制复合体(PRC)招募到没有DNA甲基化的富含CpG的DNA分子中。PRC募集不是PML核体成分(PML-NBS)可能施加的结构性异染色质作用，而是允许病毒上体获得兼性异染色质状态来建立和维持潜伏期。因此，虽然我们假设PRC介导的抑制是潜伏期的一个共同点，但我们也预计病毒染色质的初始组装和成熟在空间和/或时间上是以不同的方式进行的。我们将使用相关的体外潜伏期模型、转录组/表观基因组分析和活细胞成像来对潜伏期建立阶段进行时空研究，以破译支配病毒染色质编程的机制，并确定这一过程中涉及的关键病毒和细胞因子。在可能的第二个资助期，我们计划将我们的发现扩展到其他病毒，明确的目标是开发DNA病毒感染早期染色质调节的统一模型。

Nuclear entry of a non-chromatinized, epigenetically naïve DNA molecule is a central event in all herpesvirus infections. Following nuclear delivery, viral episomes can either activate the lytic gene expression cascade, leading to production of viral progeny and host cell death, or acquire latent chromatin states that mediate selective and reversible silencing of lytic genes. Whereas latent chromatin allows the viral genome to persist in a dormant state until a reactivation signal is received, antiviral host defences promote constitutively repressive chromatin states to globally supress invading DNA. If the virus fails to escape or manipulate these defences, viral episomes are permanently silenced or cleared.To date, the chromatin factors and epigenetic pathways governing successful establishment of latent chromatin are only partially understood. Given their evolutionary relationship, we hypothesise that as of yet undiscovered and fundamental principles are shared among different herpesviruses. To address this hypothesis, we here will perform a comparative analysis of two human herpesviruses: The gammaherpesvirus Kaposi sarcoma-associated herpesvirus (KSHV) and the alphaherpesviruses varicella zoster virus (VZV). Based on our previous observations, we hypothesize that both viruses exploit default host pathways that have evolved to rapidly recruit polycomb repressive complexes (PRC) to CpG-rich DNA molecules devoid of DNA methylation. Instead of constitutive heterochromatinization that may be imposed by components of PML nuclear bodies (PML-NBs), PRC recruitment then allows viral episomes to acquire facultative heterochromatin states to establish and maintain latency. While we therefore postulate PRC-mediated suppression to be a common denominator of latency, we also expect that initial assembly as well as maturation of viral chromatin proceed in a spatially and/or temporally distinct fashion for each virus. We will employ relevant in vitro latency models, transcriptome/epigenome analyses and live cell imaging to perform a spatiotemporal investigation of the latency establishment phase to decipher the mechanisms that govern viral chromatin programming, and to identify the key viral and cellular factors involved in this process. In a putative second funding period, we plan to extend our findings to other viruses with the explicit goal of developing a unified model of early chromatin regulation in DNA virus infection.