Project description:As a human tumor virus, EBV is present as a latent infection in its associated malignancies where genetic and epigenetic changes have been shown to impede cellular differentiation and viral reactivation. One such change is increased levels of the Wnt signaling effector, lymphoid enhancer binding factor 1 (LEF1) following EBV epithelial infection. In silico analysis of EBV type 1 and 2 genomes identified over 20 Wnt-response elements suggesting that LEF1 may directly bind the EBV genome and regulate the viral life cycle. Using CUT&RUN-seq, LEF1 was shown to bind the latent EBV genome at various sites encoding viral lytic products that included the immediate early transactivator BZLF1 and viral primase BSLF1 genes. SiRNA depletion of specific LEF1 isoforms revealed that the alternative-promoter derived isoform with an N-terminal truncation (∆N LEF1) transcriptionally repressed lytic genes associated with LEF1 binding. Furthermore, forced expression of the ∆N LEF1 isoform antagonized EBV reactivation from latency. The LEF1 mediated repression requires histone deacetylase activity through either recruitment or a direct intrinsic histone deacetylase activity. SiRNA depletion of LEF1 resulted in increased histone 3 lysine 9 and lysine 27 acetylation at LEF1 binding sites and across the EBV genome. These results support a novel role for LEF1 in maintaining EBV latency and restriction viral reactivation via repressive chromatin remodeling of critical lytic cycle factors
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 basic biology of bacteriophage–host interactions has attracted increasing attention due to a renewed interest in the therapeutic potential of bacteriophages. In addition, knowledge of the host pathways inhibited by phage may provide clues to novel drug targets. However, the effect of phage on bacterial gene expression and metabolism is still poorly understood. In this study, we tracked phage–host interactions by combining transcriptomic and metabolomic analyses in Pseudomonas aeruginosa infected with a lytic bacteriophage, PaP1. Compared with the uninfected host, 7.1% (399/5655) of the genes of the phage-infected host were differentially expressed genes (DEGs); of those, 354 DEGs were downregulated at the late infection phase. Many of the downregulated DEGs were found in amino acid and energy metabolism pathways. Using metabolomics approach, we then analyzed the changes in metabolite levels in the PaP1-infected host compared to un-infected controls. Thymidine was significantly increased in the host after PaP1 infection, results that were further supported by increased expression of a PaP1-encoded thymidylate synthase gene. Furthermore, the intracellular betaine concentration was drastically reduced, whereas choline increased, presumably due to downregulation of the choline–glycine betaine pathway. Interestingly, the choline–glycine betaine pathway is a potential antimicrobial target; previous studies have shown that betB inhibition results in the depletion of betaine and the accumulation of betaine aldehyde, the combination of which is toxic to P. aeruginosa. These results present a detailed description of an example of phage-directed metabolism in P. aeruginosa. Both phage-encoded auxiliary metabolic genes and phage-directed host gene expression may contribute to the metabolic changes observed in the host.
Project description:Lytic infection by the Epstein-Barr virus (EBV) poses numerous health risks, such as infectious mononucleosis and lymphoproliferative disorder. We demonstrate that JQ1 and other BET inhibitors block two different steps in the sequential cascade of the EBV life cycle: expression of the immediate-early gene BZLF1 and lytic genome replication. This represents a novel mode of action for antiviral drugs that may increase efficacy and decrease emergence of resistance. The ChIP-seq data below show that the BET proteins bind to both EBV lytic origins of replication.
Project description:Lytic infection by the Epstein-Barr virus (EBV) poses numerous health risks, such as infectious mononucleosis and lymphoproliferative disorder. We demonstrate that JQ1 and other BET inhibitors block two different steps in the sequential cascade of the EBV life cycle: expression of the immediate-early gene BZLF1 and lytic genome replication. This represents a novel mode of action for antiviral drugs that may increase efficacy and decrease emergence of resistance. The ChIP-seq data below show that the BET proteins bind to both EBV lytic origins of replication.