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
Project description:The establishment of latency is an essential step for the life-long persistent infection and pathogenesis of Kaposi’s 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.
Project description:Chromatin-organizing factors, like CTCF and cohesins, have been implicated in the control of complex viral regulatory programs. We investigated the role of CTCF and cohesin in the control of the latent to lytic switch for Kaposi's Sarcoma-Associated Herpesvirus (KSHV). We found that cohesin subunits, but not CTCF, were required for the repression of KSHV immediate early gene transcription. Depletion of cohesin subunits Rad21, SMC1, or SMC3 resulted in lytic cycle gene transcription and viral DNA replication. In contrast, depletion of CTCF failed to induce lytic transcription or DNA replication. ChiP-Seq analysis revealed that cohesins and CTCF bound to several sites within the immediate early control regions for ORF50 and more distal 5' sites that also regulate the divergently transcribed ORF45-46-47 gene cluster. Rad21 depletion led to a robust increase in ORF45 and ORF47 transcripts, with similar kinetics to that observed with chemical induction by sodium butyrate. During latency, the chromatin between the ORF45 and ORF50 transcription start sites was enriched in histone H3K4me3 with elevated H3K9ac at the ORF45 promoter and elevated H3K27me3 at the ORF50 promoter. A paused form of RNA pol II was loosely associated with the ORF45 promoter region during latency, but was converted to an active elongating form upon reactivation induced by Rad21 depletion. Butyrate-induced transcription of ORF45 and ORF47 was resistant to cyclohexamide, suggesting that these genes have immediate early features similar to ORF50. Butyrate-treatment caused the rapid dissociation of cohesins and loss of CTCF binding at the immediate early gene locus, suggesting that cohesins may be a direct target of butyrate-mediated lytic induction. Our findings implicate cohesins as a major repressor of KSHV lytic gene activation, and function coordinately with CTCF to regulate the switch between latent and lytic gene activity. Study of chromatin-organizing factors, like CTCF and cohesins.
Project description:The oral cavity has previously been identified as the major site for transmission of Kaposi’s sarcoma-associated herpesvirus (KSHV), but how KSHV establishes infection and replication in the oral epithelia remains unclear. Here, we report a KSHV spontaneous lytic replication model using fully differentiated, three-dimensional (3D) oral epithelial organoids at an air-liquid interface (ALI). This model revealed that KSHV infected the oral epithelia when the basal epithelial cells were exposed by damage. Unlike two-dimensional (2D) cell culture, 3D oral epithelial organoid ALI culture allowed high levels of spontaneous KSHV lytic replication, where lytically replicating cells were enriched at the superficial layer of epithelial organoid. Single cell RNA sequencing (scRNAseq) showed that KSHV infection induced drastic changes of host gene expression in infected as well as uninfected cells at the different epithelial layers, resulting in altered epithelial differentiation and morphogenesis. Moreover, we identified a unique population of infected cells containing lytic gene expression at the KSHV K2-K5 gene locus and distinct host and viral gene expression compared to latency or lytic replication. This study demonstrates an in vitro 3D epithelial organoid ALI culture model that recapitulates KSHV infection in the oral cavity, where KSHV undergoes the epithelial differentiation-dependent spontaneous lytic replication with a unique cell population carrying distinct viral gene expression.
Project description:Primari effusion lymphoma are (PEL) patient-derived transformed B-cells harboring latent Kaposi's sarcoma-associated herpesvirus (KSHV). The treatment of PEL cells with valproic acid (VA) leads to reactivation of KSHV and viral lytic replication. The aim of this project is to evaluate the effect of KSHV lytic infection on expression of the host transcriptome.
Project description:During lytic replication of Kaposi’s sarcoma-associated herpesvirus (KSHV), a nuclear viral long noncoding RNA known as PAN RNA becomes the most abundant polyadenylated transcript in the cell. Knockout or knockdown of KSHV PAN RNA results in loss of late lytic viral gene expression and, consequently, reduction of progeny virion release from the cell. We studied KSHV and RRV PAN RNA homologs using capture hybridization analysis of RNA targets (CHART) and observed their reproducible associations with host chromatin, but the loci differ between PAN RNA homologs.
Project description:Kaposi’s Sarcoma associated herpesvirus (KSHV) is an oncogenic human virus and leading cause of mortality in HIV infection. Reactivation of KSHV from latent to lytic stage infection initiates a cascade of viral gene expression, and here we show how these changes remodel the host cell proteome to enable viral replication. By undertaking a systematic and unbiased analysis of changes to the endothelial cell proteome following lytic KSHV reactivation, we quantify >7000 cellular and 71 viral proteins. Lytic KSHV infection resulted in >2-fold downregulation of 291 cellular proteins, including PKR, the key cellular sensor of double-stranded RNA. A complementary KSHV genome-wide CRISPR genetic screen identified K5 as the viral gene responsible for the downregulation of two novel KSHV targets, Nectin-2 and CD155, both ligands of the NK cell DNAM-1 receptor. Despite the high episome copy number, we show that CRISPR Cas9 provides a remarkably efficient way to target KSHV genomes.
Project description:Kaposi’s Sarcoma associated herpesvirus (KSHV) is an oncogenic human virus and leading cause of mortality in HIV infection. Reactivation of KSHV from latent to lytic stage infection initiates a cascade of viral gene expression, and here we show how these changes remodel the host cell proteome to enable viral replication. By undertaking a systematic and unbiased analysis of changes to the endothelial cell proteome following lytic KSHV reactivation, we quantify >7000 cellular and 71 viral proteins. Lytic KSHV infection resulted in >2-fold downregulation of 291 cellular proteins, including PKR, the key cellular sensor of double-stranded RNA. A complementary KSHV genome-wide CRISPR genetic screen identified K5 as the viral gene responsible for the downregulation of two novel KSHV targets, Nectin-2 and CD155, both ligands of the NK cell DNAM-1 receptor. Despite the high episome copy number, we show that CRISPR Cas9 provides a remarkably efficient way to target KSHV genomes.
Project description:Lytic replication is essential for persistent infection of Kaposi’s sarcoma-associated herpesvirus (KSHV) and the pathogenesis of related diseases, and many cellular pathways are hijacked by KSHV proteins to initiate and control the lytic replication of this virus. However, the machinery involved in KSHV lytic replication from the early to the late phases remains largely undetermined. We previously revealed that KSHV ORF45 plays important roles in late transcription and translation. In the present study, we reveal that the Forkhead box proteins FoxK1 and FoxK2 are ORF45-binding proteins and are essential for KSHV lytic gene expression and virion production and that depletion of FoxK1 or FoxK2 significantly suppresses the expression of many late viral genes. FoxK1 and FoxK2 directly bind to the promoters of several late viral genes, ORF45 augments the promoter binding and transcriptional activity of FoxK1 and FoxK2, and then FoxK1 or FoxK2 cooperates with ORF45 to promote late viral gene expression. Our findings suggest that ORF45 interacts with FoxK1 and FoxK2 and promotes their occupancy on a cluster of late viral promoters and their subsequent transcriptional activity; consequently FoxK1 and FoxK2 promote late gene expression to facilitate KSHV lytic replication.
Project description:To investigate the regulation of ER stress-related gene expression by KSHV-ORF45 during lytic replication, we performed RNA-sequencing analysis of iSLK-BAC16 vs. iSLK-STOP45 cells under lytic induction for 72h. When the differentially expressed genes were filtered and analyzed, we found that ER stress-related gene expression was much low in iSLK-STOP45 cells compared with iSLK-BAC16 cells, indicating that ORF45 expression is required for induction of ER stress.To further reveal the signal transduction of LAMP3 in KSHV lytic replication, RNA-sequencing analysis was performed to identify the differentially expressed genes (DEGs) in normal vs. LAMP3-silenced cells under lytic replication. A total of 35372 raw read targets were obtained and all DEG clusters were filtered and analyzed by KEGG pathway enrichment analysis. Eleven pathway were significantly enriched over 10 fold in LAMP3-depleted cells compared with control cells, including PI3K-Akt signaling pathway.Given that Akt and ERK activation play the important roles in KSHV lytic replication, we conclude that LAMP3 might promote Akt and ERK activation and then consequently facilitate KSHV lytic replication.