Project description:We report that the integration of the human papillomavirus into the host genome increases chromatin accessibility, transcription, and CTCF binding within 100 kbp of the integration site which promotes oncogenesis in some patients.
Project description:Distinct integration patterns of different retroviruses have puzzled virologists for over 20 years. The viral integrase (IN), as part of the intasome complex, docks onto the target DNA (tDNA) and catalyzes the insertion of the viral genome into the host chromatin. We identified retroviral IN amino acids directly contacting tDNA bases and affecting the local integration site sequence biases. These residues also determine the propensity of the virus to integrate into flexible tDNA sequences. Remarkably, natural polymorphisms INS119G and INR231G retarget viral integration away from gene dense regions, without affecting the interaction with the lentiviral tethering cofactor LEDGF/p75 (PSIP1). Precisely these variants were associated with rapid disease progression in a chronic HIV-1 subtype C infection cohort. These findings link integration site selection to virulence and viral evolution but also to the host immune response and antiretroviral therapy, since HIV-1 IN119 is under selection by HLA alleles and integrase inhibitors. LEDGF/p75 (PSIP1) ChIP-Seq using A300-848 antibody (recognizes p75 isoform) and input control in primary CD4+ T-cells
Project description:Lentivirus containing simian virus 40 large T antigen (SV40T) is routinely used to induce cell immortalization. However, the roles of viral integration itself in this progress is still controversial. Here, we transformed primary mouse embryonic fibroblasts (MEFs) with SV40T lentivirus and studied the roles of viral integration in the immortalization using RNA-seq and whole genome sequencing (WGS). During the immortalization, differentially expressed genes (DGEs) are enriched in viral infection and several diverse activities. However, DEGs between immortalized and aging cells are significantly enriched in DNA/chromosome- and extracellular matrix (ECM)-associated activities. Gene regulatory network (GRN) analysis shows that although p53 is a key regulatory factor, many other transcription factors also play critical roles in the process, like STAT1. Of these DEGs, 32 genes have viral integration in their coding and/or regulatory regions. Our findings suggest that viral integration may promote SV40T-mediated immortalization by disturbing the expression of DNA/chromosome- and ECM-associated genes.
Project description:Distinct integration patterns of different retroviruses have puzzled virologists for over 20 years. The viral integrase (IN), as part of the intasome complex, docks onto the target DNA (tDNA) and catalyzes the insertion of the viral genome into the host chromatin. We identified retroviral IN amino acids directly contacting tDNA bases and affecting the local integration site sequence biases. These residues also determine the propensity of the virus to integrate into flexible tDNA sequences. Remarkably, natural polymorphisms INS119G and INR231G retarget viral integration away from gene dense regions, without affecting the interaction with the lentiviral tethering cofactor LEDGF/p75 (PSIP1). Precisely these variants were associated with rapid disease progression in a chronic HIV-1 subtype C infection cohort. These findings link integration site selection to virulence and viral evolution but also to the host immune response and antiretroviral therapy, since HIV-1 IN119 is under selection by HLA alleles and integrase inhibitors.
Project description:Oncogenic human papillomavirus (HPV) genomes are often integrated into host chromosomes in HPV-associated cancers. HPV genomes are integrated either as a single copy, or as tandem repeats of viral DNA interspersed with, or without, host DNA. Integration occurs frequently in common fragile sites susceptible to tandem repeat formation, and the flanking or interspersed host DNA often contains transcriptional enhancer elements. When co-amplified with the viral genome, these enhancers can form super-enhancer-like elements that drive high viral oncogene expression. Here, we compiled highly curated datasets of HPV integration sites in cervical (CESC) and head and neck squamous cell carcinoma (HNSCC) cancers and assessed the number of breakpoints, viral transcriptional activity, and host genome copy number at each insertion site. Tumors frequently contained multiple distinct HPV integration sites, but often only one “driver” site that expressed viral RNA. Since common fragile sites and active enhancer elements are cell-type specific, we mapped these regions in cervical cell lines using FANCD2 and Brd4/H3K27ac ChIP-seq, respectively. Large enhancer clusters, or super-enhancers, were also defined using the Brd4/H3K27ac ChIP-seq dataset. HPV integration breakpoints were enriched at both FANCD2-associated fragile sites, and enhancer-rich regions, and frequently showed adjacent focal DNA amplification in CESC samples. We identified recurrent integration “hotspots” that were enriched for super-enhancers, some of which function as regulatory hubs for cell-identity genes. We propose that during persistent infection, extrachromosomal HPV minichromosomes associate with these transcriptional epicenters, and accidental integration could promote viral oncogene expression and carcinogenesis.
Project description:We investigated the link between HIV-1 integration by using B-HIVE and LEDGINs. B-HIVE tracks insert-specific HIV expression by tagging a unique barcode in the HIV genome. LEDGINs are antivirals that inhibit the interaction between HIV-IN and its chromatin tethering cofactor LEDGF/p75. They are known to retarget HIV-1 integration sites. Here, we confirmed that LEDGIN treatment retargets integration out of transcriptionally active regions and reduce HIV expression. Silent provirus was located at increased distance to H3K36me3, the recognition marker of LEDGF/p75, after treatment with LEDGINs. Viral RNA expression was also influenced by the proximity of enhancers, regardless of the presence of LEDGINs.
Project description:HIV-1 encounters the hierarchically organized host chromatin to stably integrate and persist in anatomically distinct latent reservoirs. The contribution of genome organization in HIV-1 infection has been largely understudied across different HIV-1 targets. Here we determine HIV-1 integration sites (IS), associate them to chromatin and expression signatures at different genomic scales in a microglia cell model and profile them together with the primary T cell reservoir. HIV-1 insertions into introns of actively transcribed genes with IS hotspots in genic- and super-enhancers, characteristic of blood cells, are maintained in the microglia cell model. Genome organization analysis reveals dynamic CCCTC-binding factor (CTCF) clusters in cells with active and repressed HIV-1 transcription, while CTCF removal impairs viral integration. We identify CTCF-enriched topologically associated domain (TAD) boundaries with signatures of transcriptionally active chromatin as HIV-1 integration determinant in microglia and CD4+ T cells, highlighting the importance of the host genome organization in HIV-1 infection.