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HSV-1 exploits host heterochromatin for egress [RNA-seq]

ABSTRACT: Herpes simplex virus replicates and forms progeny in the nucleus where it must overcome host chromatin to establish a successful infection. During lytic infection, newly formed viral capsids navigate through heterochromatin channels at the nuclear periphery to egress out of the nucleus. In uninfected cells, specific histone marks such as trimethylation on histone H3 lysine 27 (H3K27me3) and the histone variant macroH2A1 delineate heterochromatin regions, or repressed chromatin, that are predominantly located in the nuclear periphery. We examined these markers during HSV-1 lytic infection in primary cells and discovered a striking increase in the levels of macroH2A1 and H3K27me3. Here, we demonstrate that the loss of macroH2A1 results in significantly lower viral titers but does not impair viral transcription, protein production, or replication. By inhibiting the deposition of H3K27me3 by EZH2, we further show that reduction of H3K27me3 also leads to a significant decrease in viral titers. Through chromatin profiling via Cleavage Under Targets and tagmentation (CUT&Tag) of macroH2A1 and H3K27me3, we define the specific chromatin regions that change dynamically during HSV-1 lytic infection and show that regions with increased macroH2A1 and H3K27me3 correlate with decreased host transcription as measured by RNA-seq. Furthermore, we find by electron microscopy that loss of macroH2A1 results in reduced heterochromatin at the nuclear periphery and significantly more viral capsids trapped in the nuclear compartment. Using both high and low shedding clinical isolates of HSV-1, we similarly find that HSV-1 titers are significantly reduced in the absence of macroH2A1. Our work demonstrates that HSV-1 takes advantage of the dynamic nature of host heterochromatin formation during infection for efficient viral egress from the nuclear compartment.

ORGANISM(S): Homo sapiens

PROVIDER: GSE209632 | GEO | 2023/07/01

REPOSITORIES: GEO

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Project description:The establishment of latency is an essential step for the life-long persistent infection and pathogenesis of KaposiM-bM-^@M-^Ys sarcoma-associated herpesvirus (KSHV). While the KSHV genome is chromatin-free in the virions, the viral DNA in latently infected cells has a chromatin structure that is characterized by a specific pattern of activating and repressive histone modifications that ultimately promote latent gene expression while suppressing lytic gene expression. To investigate the molecular events involved in the establishment of the latent chromatin structure during the pre-latency phase of KSHV infection, we performed a comprehensive epigenetic study to analyze the recruitment of chromatin regulatory factors onto the KSHV genome at various time-points following de novo infection of SLK and TIME cells. This showed that the KSHV genome undergoes a biphasic chromatinization following de novo infection. Initially, a transcriptionally active chromatin (euchromatin), characterized by high levels of the H3K4me3 and acetylated H3K27 (H3K27ac) activating histone marks, was deposited on the viral episome and was accompanied by the temporary induction of a limited number of lytic genes. Interestingly, transient expression of the RTA protein facilitated the increases of H3K4me3 and H3K27ac occupancy on the KSHV episome during de novo infection. Between 24-72 hours post-infection, as the levels of these activating histone marks declined on the KSHV genome, the levels of the repressive H3K27me3 and H2AK119ub histone marks increased concomitantly with the decline of lytic gene expression. Importantly, this transition to heterochromatin was dependent on both the Polycomb Repressive Complex 2 and 1. In contrast, upon infection of human gingiva-derived epithelial cells, the KSHV genome underwent a continuously transcription-active euchromatinization, resulting in efficient lytic gene expression. Our data demonstrate that the KSHV genome undergoes a temporally ordered biphasic euchromatin-to-heterochromatin transition in endothelial cells, leading to latent infection, whereas KSHV preferentially adopts a transcriptionally active euchromatin in oral epithelial cells, resulting in lytic gene expression. Our results suggest that the differential epigenetic modification of the KSHV genome in distinct cell types is a potential determining factor for latent infection vs. lytic replication of KSHV. Please see above. 16 hybridizations: ChIP and Input DNA

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HSV-1 exploits host heterochromatin for egress [RNA-seq]

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