Roberts Ashley P E, Orr Anne, Iliev Victor, Orr Lauren, McFarlane Steven, Yang Zhousiyu, Epifano Ilaria, Loney Colin, Rodriguez Milagros Collados, Cliffe Anna R, Conn Kristen L, Boutell Chris
MRC-University of Glasgow Centre for Virus Research (CVR), Sir Michael Stoker Building, Garscube Campus, Glasgow, Scotland, UK.
School of Life and Environmental Sciences, College of Health and Science, Joseph Banks laboratories, University of Lincoln, Brayford Pool Campus, Lincoln, LN6 7TS, UK.
bioRxiv. 2024 Aug 15:2024.08.15.608064. doi: 10.1101/2024.08.15.608064.
Herpesviruses are ubiquitous pathogens that cause a wide range of disease. Upon nuclear entry, their genomes associate with histones and chromatin modifying enzymes that regulate the progression of viral transcription and outcome of infection. While the composition and modification of viral chromatin has been extensively studied on bulk populations of infected cells by chromatin immunoprecipitation, this key regulatory process remains poorly defined at single-genome resolution. Here we use high-resolution quantitative imaging to investigate the spatial proximity of canonical and variant histones at individual Herpes Simplex Virus 1 (HSV-1) genomes within the first 90 minutes of infection. We identify significant population heterogeneity in the stable enrichment and spatial proximity of canonical histones (H2A, H2B, H3.1) at viral DNA (vDNA) relative to established promyelocytic leukaemia nuclear body (PML-NB) host factors that are actively recruited to viral genomes upon nuclear entry. We show the replication-independent histone H3.3/H4 chaperone Daxx to cooperate with PML to mediate the enrichment and spatial localization of variant histone H3.3 at vDNA that limits the rate of HSV-1 genome decompaction to restrict the progress of immediate-early (IE) transcription. This host response is counteracted by the viral ubiquitin ligase ICP0, which degrades PML to disperse Daxx and variant histone H3.3 from vDNA to stimulate the progression of viral genome expansion, IE transcription, and onset of HSV-1 replication. Our data support a model of intermediate and sequential histone assembly initiated by Daxx that limits the rate of HSV-1 genome decompaction independently of the stable enrichment of histones H2A and H2B at vDNA required to facilitate canonical nucleosome assembly. We identify HSV-1 genome decompaction upon nuclear infection to play a key role in the initiation and functional outcome of HSV-1 lytic infection, findings pertinent to the transcriptional regulation of many nuclear replicating herpesvirus pathogens.
疱疹病毒是引起广泛疾病的普遍存在的病原体。进入细胞核后，它们的基因组与组蛋白和染色质修饰酶结合，这些酶调节病毒转录的进程和感染的结果。虽然通过染色质免疫沉淀在大量受感染细胞群体中对病毒染色质的组成和修饰进行了广泛研究，但在单基因组分辨率下，这个关键的调控过程仍然定义不明确。在这里，我们使用高分辨率定量成像技术，研究单纯疱疹病毒1型（HSV-1）感染后最初90分钟内，单个病毒基因组上经典组蛋白和变体组蛋白的空间接近性。我们发现，相对于在细胞核进入时被积极招募到病毒基因组的既定早幼粒细胞白血病核体（PML-NB）宿主因子，病毒DNA（vDNA）上经典组蛋白（H2A、H2B、H3.1）的稳定富集和空间接近性存在显著的群体异质性。我们发现，不依赖复制的组蛋白H3.3/H4伴侣蛋白Daxx与PML协同作用，介导变体组蛋白H3.3在vDNA上的富集和空间定位，这限制了HSV-1基因组解压缩的速度，从而限制了立即早期（IE）转录的进程。这种宿主反应被病毒泛素连接酶ICP0抵消，ICP0降解PML，使Daxx和变体组蛋白H3.3从vDNA上分散，以刺激病毒基因组扩增、IE转录和HSV-1复制的开始。我们的数据支持一种由Daxx启动的中间和顺序组蛋白组装模型，该模型限制了HSV-1基因组解压缩的速度，而与促进经典核小体组装所需的vDNA上组蛋白H2A和H2B的稳定富集无关。我们确定核感染时HSV-1基因组的解压缩在HSV-1裂解感染的起始和功能结果中起关键作用，这些发现与许多核复制疱疹病毒病原体的转录调控相关。
