ABSTRACT: The chromatin modification by SUMO-2/3 and SUMO-1 prevents the epigenetic activation of key immune-related genes during Kaposi’s sarcoma associated herpesvirus reactivation
Project description:Kaposi’s Sarcoma Herpesvirus (KSHV) is the causative agent of Kaposi’s Sarcoma (KS) and isassociated with primary effusion lymphoma (PEL), multicentric Castleman’s disease (MCD) and two inflammatory diseases. KSHV-associated cancers are primarily associated with genes expressed during latency, while other pathologies are associated with lytic gene expression. The major lytic switch of the virus, RTA, interacts with cellular machinery to co-opt the host ubiquitin proteasome system to evade the immune response as well as activate the program of lytic replication. Through SILAC labeling, ubiquitin remnant enrichment and mass spectrometry, we have analyzed the RTA dependent ubiquitin-modified proteome. We identified RTA dependent changes in the populations of polyubiquitin chains, as well as changes in ubiquitinated proteins in both cells expressing RTA and naturally infected cells following lytic reactivation. We observed an enrichment of proteins that are also reported to be SUMOylated, suggesting that RTA, a SUMO targeting ubiquitin ligase, may function to alleviate a SUMO dependent block to lytic reactivation. RTA targeted substrates directly through a ubiquitin ligase domain dependent mechanism as well as indirectly through cellular ubiquitin ligases, including RAUL. Our ubiquitome analysis revealed an RTA dependent mechanism of immune evasion. We provide evidence of inhibition of TAP dependent peptide transport, resulting in decreased HLA complex stability. The results of this analysis increase our understanding of mechanisms governing the latent to lytic transition in addition to the identification of a novel RTA dependent mechanism of immune evasion.Kaposi’s Sarcoma Herpesvirus (KSHV) is the causative agent of Kaposi’s Sarcoma (KS) and is associated with primary effusion lymphoma (PEL), multicentric Castleman’s disease (MCD) and two inflammatory diseases. KSHV-associated cancers are primarily associated with genes expressed during latency, while other pathologies are associated with lytic gene expression. The major lytic switch of the virus, RTA, interacts with cellular machinery to co-opt the host ubiquitin proteasome system to evade the immune response as well as activate the program of lytic replication. Through SILAC labeling, ubiquitin remnant enrichment and mass spectrometry, we have analyzed the RTA dependent ubiquitin-modified proteome. We identified RTA dependent changes in the populations of polyubiquitin chains, as well as changes in ubiquitinated proteins in both cells expressing RTA and naturally infected cells following lytic reactivation. We observed an enrichment of proteins that are also reported to be SUMOylated, suggesting that RTA, a SUMO targeting ubiquitin ligase, may function to alleviate a SUMO dependent block to lytic reactivation. RTA targeted substrates directly through a ubiquitin ligase domain dependent mechanism as well as indirectly through cellular ubiquitin ligases, including RAUL. Our ubiquitome analysis revealed an RTA dependent mechanism of immune evasion. We provide evidence of inhibition of TAP dependent peptide transport, resulting in decreased HLA complex stability. The results of this analysis increase our understanding of mechanisms governing the latent to lytic transition in addition to the identification of a novel RTA dependent mechanism of immune evasion.
Project description:Understanding protein-protein interaction (PPI) network dynamics is key to understanding nominal and perturbed cell states. Here, we develop a new machine learning framework called Tapioca that allows for the study of PPIs in dynamics contexts at a global scale in ex/in vivo conditions. Furthermore, we optimized the thermal denaturation and lysis conditions used in the thermal proximity coaggregation (TPCA) methodology, one of the types of data Tapioca can use to make predictions. Using this optimized protocol and Tapioca, we investigated the temporal dynamics of reactivation from latency of the oncogenic gammaherpesvirus Kaposi’s sarcoma-associated herpesvirus (KSHV), identifying the host protein NUCKS1 as a factor promoting KSHV genome replication during lytic infection. Integrating this dataset with published TPCA datasets from the alphaherpesvirus herpes simplex virus type-1 (HSV-1) and the betaherpesvirus human cytomegalovirus (HCMV), we determined NUCKS1 to have a proviral role across all three herpesvirus subfamilies.
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:The epitranscriptomic modification m6A is a ubiquitous feature of the mammalian transcriptome. It modulates mRNA fate and dynamics to exert regulatory control over numerous cellular processes and disease pathways, including viral infection. Kaposi’s sarcoma-associated herpesvirus (KSHV) reactivation from the latent phase leads to redistribution of m6A topology upon both viral and cellular mRNAs within infected cells. Here we investigate the role of m6A in cellular transcripts upregulated during KSHV lytic replication. Results show that m6A is crucial for the stability of the GPRC5A mRNA, whose expression is induced by the KSHV latent-lytic switch master regulator, the replication and transcription activator (RTA) protein. Moreover, we demonstrate that GPRC5A is essential for efficient KSHV lytic replication by directly regulating NFκB signalling. Overall, this work highlights the central importance of m6A in modulating cellular gene expression to influence viral infection.
Project description:Herpesviruses are a group of double-stranded DNA viruses known to develop versatile viral strategies to escape host immune surveillance for promoting their replication and propagation. This is illustrated by Kaposi’s sarcoma-associated herpesvirus (KSHV), an oncogenic gamma-herpesvirus that overcomes host immune suppression by multiple mechanisms. In this study, we reported that KSHV dysregulates 5-methylcytosine (m5C) modification and mRNA stability of host antiviral factors to benefit its lytic replication. KSHV lytic reactivation or de novo challenge led to downregulation of m5C RNA methyltransferases, NSUN2 and NSUN1 (NSUN2/1), while NSUN2/1 depletion promoted KSHV lytic replication. We further performed the RNA bisulfite sequencing (RNA-BS-seq) to identify KSHV-dependent m5C modification of host mRNAs. Overall, our results highlighted a new strategy for human gamma-herpesviruses to counteract host antiviral factors and promote their lytic replication by manipulating host m5C RNA methylation.
Project description:Enhancers play indispensable roles in cell proliferation and survival through spatiotemporally regulating gene transcription. In addition, active enhancers and super-enhancers often produce noncoding enhancer RNAs (eRNAs) that precisely control RNA polymerase II activity. Kaposi’s sarcoma-associated herpesvirus (KSHV) is a human oncogenic gamma-2 herpesvirus that causes Kaposi’s sarcoma and lymphoproliferative diseases of B-cell origin such as primary effusion lymphoma (PEL). It is well characterized that KSHV utilizes host epigenetic and nuclear machineries to control the switch between two life cycles, latency and lytic replication. However, how KSHV impacts the host epigenome at different stages of viral life cycle is not well understood. Using the analysis of global run-on sequencing (GRO-seq) and chromatin-immunoprecipitation sequencing (ChIP-seq), we profiled the dynamics of host transcriptional regulatory elements during latency and lytic replication of KSHV-infected PEL cells. This study showed that a number of critical host genes for KSHV latency, including MYC proto-oncogene, were under the control of super-enhancers and eRNAs that were globally repressed upon viral reactivation. A combination of circular chromosome conformation capture combined with sequencing (4C-seq), GRO-seq and ChIP-seq indicated that the eRNA-expressing super-enhance regions were located at downstream of the MYC gene in KSHV-infected PELs. Treatment of an epigenetic drug to block enhancer function or shRNA-mediated depletion of the eRNA expression significantly reduced MYC mRNA expression in KSHV-infected PELs. Finally, while cellular IRF4 acted upon the eRNAs and super-enhancers for MYC expression during latency, the KSHV viral IRF4 repressed cellular IRF4 expression upon reactivation, decreasing MYC expression and thereby, facilitating lytic replication. Taken together, these data suggest that KSHV acts as an epigenetic driver that modifies host epigenomic status by effectively regulating enhancer function upon reactivation.
Project description:Epstein-Barr virus (EBV) uses a biphasic lifecycle of latency and lytic reactivation to infect >95% of adults worldwide. Despite its central role in EBV persistence and oncogenesis, much remains unknown about how EBV latency is maintained. We used a human genome-wide CRISPR/Cas9 screen to identify that the nuclear protein SFPQ was critical for latency. SFPQ supported expression of linker histone H1, which stabilizes nucleosomes and regulates nuclear architecture, but has not been previously implicated in EBV gene regulation. H1 occupied latent EBV genomes, including the immediate early gene BZLF1 promoter. Upon reactivation, SFPQ was sequestered into sub-nuclear puncta, and EBV genomic H1 occupancy diminished. Enforced H1 expression blocked EBV reactivation upon SFPQ knockout, confirming it as necessary downstream of SFPQ. SFPQ knockout triggered reactivation of EBV in B and epithelial cells as well as in Kaposi’s Sarcoma Associated Herpesvirus, suggesting a conserved gamma-herpesvirus role. These findings highlight SFPQ as a major regulator of H1 expression and EBV latency.