Systematic Identification of Factors Crucial for Provirus Silencing in Embryonic Stem Cells (ChIP-seq)
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ABSTRACT: Our study reports the first genome-wide atlas of functional nodes that mediate proviral silencing in ESCs. It provides evidences for the comprehensive, interconnected and multi-layered genetic/epigenetic machineries by which ESCs maintain the repressive state of provirus and ERVs.
Project description:Our study reports the first genome-wide atlas of functional nodes that mediate proviral silencing in ESCs. It provides evidences for the comprehensive, interconnected and multi-layered genetic/epigenetic machineries by which ESCs maintain the repressive state of provirus and ERVs. ChIP-seq analysis of Chaf1a, Trim28, Sumo2 and Zfp809 to demonstrate the mechanism of the silencing of Endogenous retroviruses
Project description:Our study reports the first genome-wide atlas of functional nodes that mediate proviral silencing in ESCs. It provides evidences for the comprehensive, interconnected and multi-layered genetic/epigenetic machineries by which ESCs maintain the repressive state of provirus and ERVs.
Project description:Our study reports the first genome-wide atlas of functional nodes that mediate proviral silencing in ESCs. It provides evidences for the comprehensive, interconnected and multi-layered genetic/epigenetic machineries by which ESCs maintain the repressive state of provirus and ERVs. RNA-seq analysis to determine the regulated endogenous retroviruses by Histone chaperones (Chaf1a/b), sumoylation factors (Sumo2/ Ube2i/Sae1/Uba2/Senp6) and chromatin modifiers (Trim28/Eset/Atf7ip)
Project description:Human immunodeficiency virus (HIV) infection is a chronic condition, where viral DNA integrates into the genome. The fate of the provirus determines the infection course. Latently infected cells form a persistent, heterogeneous reservoir. The reservoir that reinstates an active infection comprises cells with intact provirus that can be reactivated. We confirmed that latent cells from patients exhibited active transcription throughout the provirus. To find transcriptional determinants, we characterized the establishment and maintenance of latency during proviral chromatin maturation in primary CD4+ T-cells for four months after HIV infection. As heterochromatin (marked with H3K9me3 or H3K27me3) gradually stabilized, the provirus became less accessible and lost activation potential. In a subset of infected cells, active marks (i.e., H3K27ac) remained detectable, even after prolonged proviral silencing. After T-cell activation, the proviral activation occurred uniquely in cells with H3K27ac-marked proviruses. Our observations suggested that, after transient proviral activation, cells were actively returned to latency.
Project description:Endogenous retroviruses (ERVs) were usually silenced by various histone modifications on histone H3 variants and respective histone chaperones in embryonic stem cells (ESCs). However, it is still unknown whether chaperones of other histones could repress ERVs. Here, we show that H2A/H2B histone chaperone FACT plays a critical role in silencing ERVs and ERV-derived cryptic promoters in ESCs. Loss of FACT component Ssrp1 activated MERVL whereas the re-introduction of Ssrp1 rescued the phenotype. Additionally, Ssrp1 interacted with MERVL and suppressed cryptic transcription of MERVL-fused genes. Remarkably, Ssrp1 interacted with and recruited H2B deubiquitinase Usp7 to Ssrp1 target genes. Suppression of Usp7 caused similar phenotypes as loss of Ssrp1. Furthermore, Usp7 acted by deubiquitinating H2Bub and thereby repressed the expression of MERVL-fused genes. Taken together, our study uncovers a unique mechanism by which FACT complex silences ERVs and ERV-derived cryptic promoters in ESCs.
Project description:In this study, we determined the effect of proviral inducibility on CD8+ T cell recognition of HIV-infected clones. We showed that a T cell clone containing a provirus integrated in relatively transcriptionally inactive site was much less recognized by CD8+ T cells than a T cell clone containing a provirus that was integrated into a trancriptionally active site.
Project description:We propose a technology B-HIVE, which allows us to map HIV integrations in a cell population and measure their individual transcription. The principle of B-HIVE is to tag individual viral genomes with a unique barcode of 20 nucleotides that allows us to track the viral transcripts produced by each provirus in the cell population.
Project description:Genome stability relies on epigenetic mechanisms that enforce repression of endogenous retroviruses (ERVs). Current evidence suggests that distinct chromatin-based mechanisms repress ERVs in cells of embryonic origin (histone methylation-dominant) versus more differentiated cells (DNA methylation-dominant). However, the latter aspect of this model has not been tested. Remarkably, and in contrast to the prevailing model, we find that repressive histone methylation catalyzed by the enzyme SETDB1 is critical for suppression of specific ERV families and exogenous retroviruses in committed B-lineage cells from adult mice. The profile of ERV activation in SETDB1-deficient B cells is distinct from that observed in corresponding embryonic tissues, despite the loss of repressive chromatin modifications at all ERVs. We provide evidence that, upon loss of SETDB1, ERVs are activated in a lineage-specific manner depending on the set of transcription factors available to target proviral regulatory elements. These findings have important implications for genome stability in somatic cells, as well as the interface between epigenetic repression and viral latency. Expression profiling and bisulfite PCR sequencing in Setdb1 C/C and Setdb1 D/D pro-B cells