Baker Institute for Animal Health and Department of Microbiology and Immunology, Cornell University, Ithaca, New York, USA.
Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.
J Virol. 2024 Apr 16;98(4):e0201523. doi: 10.1128/jvi.02015-23. Epub 2024 Mar 7.
Herpes simplex virus 1 (HSV-1) transcription is restricted in latently infected neurons and the genomes are in mostly silenced chromatin, whereas all viral genes are transcribed in lytically infected cells, in which the genomes are dynamically chromatinized. Epigenetic regulation modulates HSV-1 transcription during lytic, latent, and reactivating infections but the precise mechanisms are not fully defined. Nucleosomes are dynamic: they slide, breathe, assemble, and disassemble. We and others have proposed that the most dynamic HSV-1 chromatin is transcriptionally competent, whereas the least dynamic is silenced. However, the mechanisms yielding the unusually dynamic viral chromatin remain unknown. Histone variants affect nucleosome dynamics. The dynamics of H2A, H2A.X, and macroH2A were enhanced in infected cells, whereas those of H2A.B were uniquely decreased. We constructed stably transduced cells expressing tagged histone H2A, H2A.B, macroH2A, or H2B, which assembles the H2A/H2B nucleosome dimers with all H2A variants. All H2A variants, as well as ectopic and endogenous H2B were assembled into HSV-1 chromatin evenly throughout the genome but canonical H2A was relatively depleted whereas H2A.B was enriched, particularly in the most dynamic viral chromatin. When viral transcription and DNA replication were restricted, H2A.B became as depleted from the viral chromatin through the entire genome as H2A. We propose that lytic HSV-1 nucleosomes are enriched in the dynamic variant H2A.B/H2B dimers to promote HSV-1 chromatin dynamics and transcriptional competency and conclude that the dynamics of HSV-1 chromatin are determined in part by the H2A variants.
Herpes simplex virus 1 (HSV-1) transcription is epigenetically regulated during latent and lytic infections, and epigenetic inhibitors have been proposed as potential antiviral drugs to modulate latency and reactivation. However, the detailed epigenetic mechanisms of regulation of HSV-1 transcription have not been fully characterized and may differ from those regulating cellular transcription. Whereas lytic HSV-1 chromatin is unusually dynamic, latent silenced HSV-1 chromatin is not. The mechanisms resulting in the unique dynamics of the lytic chromatin remain unknown. Here we identify the enrichment of the highly dynamic histone 2A variant H2A in the most dynamic viral chromatin, which provides a mechanistic understanding of its unique dynamics. Future work to identify the mechanisms of enrichment in H2A.B on the viral chromatin may identify novel druggable epigenetic regulators that modulate HSV-1 latency and reactivation.
单纯疱疹病毒 1（HSV-1）转录在潜伏感染的神经元中受到限制，基因组处于大多数沉默的染色质中，而所有病毒基因在裂解感染的细胞中均被转录，在这些细胞中，基因组处于动态染色质状态。表观遗传调控调节 HSV-1 在裂解、潜伏和再激活感染期间的转录，但确切的机制尚未完全定义。核小体是动态的：它们滑动、呼吸、组装和拆卸。我们和其他人已经提出，最动态的 HSV-1 染色质具有转录能力，而最不动态的染色质则被沉默。然而，产生异常动态病毒染色质的机制尚不清楚。组蛋白变体影响核小体动力学。感染细胞中 H2A、H2A.X 和 macroH2A 的动力学增强，而 H2A.B 的动力学则独特地降低。我们构建了稳定转导的细胞，表达标记的组蛋白 H2A、H2A.B、macroH2A 或 H2B，这些细胞与所有 H2A 变体一起组装 H2A/H2B 核小体二聚体。所有 H2A 变体以及异位和内源性 H2B 均匀地组装到 HSV-1 基因组中的染色质中，但规范的 H2A 相对耗尽，而 H2A.B 则富集，特别是在最动态的病毒染色质中。当病毒转录和 DNA 复制受到限制时，H2A.B 从整个基因组中的病毒染色质中耗尽的程度与 H2A 一样。我们提出，裂解的 HSV-1 核小体富含动态变体 H2A.B/H2B 二聚体，以促进 HSV-1 染色质动力学和转录能力，并得出结论，HSV-1 染色质的动力学部分由 H2A 变体决定。
单纯疱疹病毒 1（HSV-1）的转录在潜伏和裂解感染期间受到表观遗传调控，并且已经提出表观遗传抑制剂作为潜在的抗病毒药物来调节潜伏和再激活。然而，HSV-1 转录的详细表观遗传调控机制尚未完全表征，并且可能与调节细胞转录的机制不同。虽然裂解的 HSV-1 染色质异常动态，但潜伏的沉默 HSV-1 染色质不是。导致裂解染色质独特动力学的机制尚不清楚。在这里，我们确定了富含高度动态的组蛋白 2A 变体 H2A 的病毒染色质最动态，这为其独特动力学提供了机制上的理解。未来识别 H2A.B 在病毒染色质上富集的机制可能会确定新的可靶向的表观遗传调节剂，从而调节 HSV-1 的潜伏和再激活。
