Development of a single domain antibody to target a G-quadruplex located on the hepatitis B virus covalently closed circular DNA Genome
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE254033 | GEO | 2026/02/02
REPOSITORIES: GEO
Similar Datasets
Project description:Hepatitis B virus (HBV) infection represents a significant public health burden worldwide. Covalently closed circular DNA (cccDNA) is the transcriptional template of HBV, which interacts with both host and viral proteins to form minichromosome in the nucleus and exhibits resistance to antiviral agents. Here, we provide evidence that ZNF638 mediates transcriptional silencing of HBV cccDNA. Mechanically, ZNF638 bound to HBV cccDNA, increasing the occupancy of HUSH complex to target loci, which subsequently recruited SETDB1, leading to enhanced H3K9me3 modification, thereby repressing cccDNA transcription. Our research findings improved the existing understanding of ZNF638- and HUSH-mediated epigenetic silencing on viral DNA, that (1) ZNF638 and HUSH complex inhibited HBV transcription, not only by epigenetic silencing extrachromosome cccDNA but also silencing the integrate viral DNA, and (2) ZNF638- and HUSH-mediated repression appeared to function as an epigenetic rheostat: occupancy of HUSH components at the locus inhibited transcription; release from the target locus activated transcription. In summary, the study demonstrates a novel epigenetic role of ZNF638 and HUSH complex in negatively regulating HBV cccDNA transcription by deposit repressive H3K9me3 histone marks and highlights the importance of epigenetic therapy targeting cccDNA, suggesting that ZNF638 could be a potential target for epigenetic therapy of viral diseases.
2026-03-20 | GSE262365 | GEO
Project description:Hepatitis B virus (HBV) contains a partially double-stranded relaxed circular DNA (rcDNA) genome that is converted into a covalently closed circular DNA (cccDNA) in the nucleus of infected hepatocyte by cellular DNA repair machinery. cccDNA associates with nucleosomes to form a minichromosome that transcribes RNA to support the expression of viral proteins and reverse transcriptional replication of viral DNA. In addition to the de novo synthesis from incoming virion rcDNA, cccDNA can also been synthesized from rcDNA in the progeny nucleocapsids in the cytoplasm of infected hepatocytes via the intracellular amplification pathway. In our efforts to identify cellular DNA repair proteins required for cccDNA synthesis by a chemogenetic screen, we found that B02, a small molecular inhibitor of DNA homologous recombination repair protein RAD51, significantly enhanced the synthesis of cccDNA via intracellular amplification pathway in human hepatoma cells. Ironically, neither siRNA knockdown of RAD51 expression nor treatment with another structurally distinct RAD51 inhibitor or activator altered cccDNA amplification. However, further mechanistic studies revealed that B02 treatment significantly elevated the levels of multiple heat shock protein mRNA and siRNA knockdown of HSPA1A expression or treatment with HSPA1 inhibitors significantly attenuated B02 enhancement of cccDNA amplification. Moreover, B02 enhanced cccDNA amplification was efficiently inhibited by compounds that selectively inhibit DNA polymerase α or topoisomerase II, the enzymes required for cccDNA intracellular amplification. Our results thus indicate that B02 treatment induces a heat shock protein-mediated cellular response that positively regulates the conversion of rcDNA into cccDNA via the authentic intracellular amplification pathway
2022-12-08 | GSE209863 | GEO
Project description:: Hepatitis B virus (HBV) remains a major public health threat with more than 296 million people chronically infected worldwide at high risk to develop hepatocellular carcinoma. Current therapies are effective in suppressing HBV replication but rarely lead to cure. The fundamental limitation rests on the fact that current therapies do not affect the HBV covalently closed circular DNA (cccDNA), which serves as the template for viral transcription and replication and is highly stable in infected cells to ensure viral persistence. In this study, we aim to identify and elucidate the functional role of cccDNA-associated host factors using affinity purification and protein mass spectrometry in HBV-infected cells. HBV core protein (HBc) is associated with cccDNA. We used an anti-HBc antibody to pull down HBcAg-associated cccDNA complex in nuclear extract of HBV-infected HepG2-NTCP cells. By protein mass spectrometry, we identified many host proteins, including previously known proteins, that are associated with HBV cccDNA. Some of these proteins were functionally validated to play a role in HBV cccDNA activities.
2024-06-16 | PXD042733 | Pride
Project description:Background & Aims: Hepatitis B virus (HBV) infection is a major health burden worldwide and currently there is no cure. The persistence of HBV covalently closed circular DNA (cccDNA) is the major obstacle for antiviral treatment. HBV core protein (HBc) has merged as a promising antiviral target, as it plays important roles in critical steps of viral life cycle. However, whether HBc could regulate HBV cccDNA transcription remains to be illustrated. Methods: Synthesized HBV cccDNA and HBVcircle with or without HBc deficiency were transfected into hepatocytes. A recently reported Adeno-Associated Virus (AAV) mediated HBV cccDNA mouse model was employed. Two capsid assembly modulators (CAMs) were used. HBV replication markers were evaluated. Chromatin immunoprecipitation (ChIP) or ChIP sequencing assays were conducted with different transcription factors, histones and RNA polymerase 2. Results: In HBV cccDNA and HBVcircle transfection assays, lack of HBc showed no effect on transcription of HBV RNA as well as HBV surface antigen production. Reconstitution of HBc did not change cccDNA derived HBV markers. Similar results were obtained in vivo, from mouse cccDNA model. ChIP data revealed similar transcription regulation of HBc deficient cccDNA chromatin with wide type cccDNA. Furthermore, CAMs treatment could not alter cccDNA transcription. Conclusions: Our results indicate that HBc neither affects histone modifications and transcription factors binding of cccDNA, nor influences cccDNA transcription. Although CAMs could reduce HBc binding to cccDNA, it does not suppress cccDNA transcriptional activity. Thus, therapeutic targeting capsid or HBc is not sufficient to reduce cccDNA transcription.
2022-04-01 | GSE199653 | GEO
Project description:To identify the cellular genes that mediate IFN-α suppression of cccDNA transcription, the total intracellular RNA were extracted from untreated or recombinant chicken IFN-α (rChIFN-α)-treated cells, and mRNA sequencing (mRNA-Seq) assays were performed in triplicate. And we found that treatment of dstet5 cells with 10 ng/ml of rChIFN-α for 6 h altered the expression of more than 100 cellular genes by more than 2 folds.
2020-06-17 | GSE134325 | GEO
Project description:Hepatitis B virus (HBV) persists by depositing a covalently closed circular DNA (cccDNA) in the nucleus of infected cells that cannot be targeted by available antivirals. Cytokine treatments can diminish HBV cccDNA via APOBEC3-mediated deamination. Here we show that overexpression of APOBEC3A alone, however, was not sufficient to reduce cccDNA in HBV-infected cells. This required addition of interferon indicating that cccDNA degradation requires an additional, interferon-stimulated gene (ISG). Transcriptome analyses identified ISG20 as the only type I and II interferon-induced, nucleus-resident protein with annotated nuclease activity. ISG20 expression was detected in human livers in acute, self-limiting but not in chronic hepatitis B. ISG20 depletion abolished the interferon-induced loss of cccDNA, and co-expression of ISG20 and APOBEC3A was sufficient to diminish cccDNA. In conclusion, non-cytolytic HBV cccDNA decline requires induction of a deaminase and nuclease. Our findings highlight that ISGs cooperate for their antiviral function and this cooperativity may be explored for therapeutic targeting.
2021-04-22 | PXD019285 | Pride
Project description:Chronic infection of Hepatitis B virus (HBV) remains a public health problem worldwide. HBV infection relies on the persistence of covalently closed circular DNA (cccDNA) in the nucleus and actively cccDNA transcription. To understand HBV cccDNA transcription regulation at single cell level, we isolated primary human hepatocytes from liver humanized FRG mice infected by one or more (two or three) HBV genotypes, and we quantified transcripts of HBV structural genes in single cells. HBV transcripts were ascribed to the transcription of individual HBV genes by 5’ end sequencing thus avoiding the ambiguity caused by the overlap of viral genome coding at the 3’ ends. Transcripts from different cccDNA in single cells were separated according to the single-nucleotide polymorphism (SNP) among different HBV genotypes. We found that the transcription of HBV follows “all-or-none” pattern in single cells: either all of the individual cccDNA molecules actively transcribe simultaneously, or, none of them generates transcripts of the structural genes. In vitro cell infection assays with recombinant HBV are consistent with the sequencing results of ex vivo samples from natural HBV infection, and also confirm that such a pattern is apparently controlled by the expression of HBx protein. These results strongly support a synchronized transcription model of HBV cccDNA molecules in single hepatocytes, and provide new insight helpful for developing HBV cure strategy.
2022-12-01 | GSE156690 | GEO
Project description:Covalently closed circular DNA (cccDNA) forms the basis for replication and persistence of hepatitis B virus (HBV) in the chronically infected liver. In this study we sought to identify host factors interacting with the HBV genome. Nucleolin (Ncl) was identified as a potential interactor of HBV cccDNA. This interaction was veriefied using an established ChIPseq protocol. The data show that Ncl binds cccDNA albeit at lower levels than HBcAg. Ncl deposition occurs across the genome without a clear localization and a variable pattern of deposition between experiments. This verifies the interaction of Ncl with HBV-cccDNA.
2021-12-31 | GSE123715 | GEO
Project description:Chronic hepatitis B virus (HBV) infection affects 240 million people worldwide and is a major risk factor for liver failure and hepatocellular carcinoma. Current antiviral therapy inhibits cytoplasmic HBV genomic replication, but is not curative since it does not eliminate nuclear HBV cccDNA, the genomic form that templates viral transcription and sustains viral persistence. Novel approaches that directly target the transcriptional regulation of cccDNA would therefore be highly desirable. cccDNA is assembled with cellular histone proteins into chromatin, but little is known about the regulation of HBV chromatin by histone posttranslational modifications (PTMs). Here, using a new cccDNA ChIP-Seq approach, we report the first genome-wide maps of PTMs in cccDNA-containing chromatin from de novo infected HepG2 cells, primary human hepatocytes and from HBV infected liver tissue. We find high levels of PTMs associated with active transcription enriched at specific sites within the HBV genome, and surprisingly very low levels of PTMs linked to transcriptional repression even at silent HBV promoters. We show that transcription and active PTMs in HBV chromatin are reduced by the activation of an innate immunity pathway, and that this can be recapitulated with a small molecule epigenetic modifying agent, opening the possibility that chromatin-based regulation of cccDNA transcription could be a new therapeutic approach to chronic HBV infection.
2015-10-08 | GSE68402 | GEO
Project description:Hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) persists as minichromosomes in the nuclei of hepatocytes and serves as the transcriptional template for viral RNAs. The cccDNA pool, characterized by a low copy number, poses challenges for cccDNA research. To accurately mimic the full-length sequences and structure of HBV cccDNA, we developed a novel method using an M13 phage-based system and deoxyribozyme to produce full-length single-strand DNA (ssDNA) corresponding to both the positive and negative strands of cccDNA. This method involves the cyclization of the ssDNA followed by the addition of T4 DNA ligase, thereby producing the cccDNA. The in vitro cyclized cccDNA, formed by M13 phage-derived single-stranded DNA (McccDNA), allows the formation of minichromosomes in transiently transfected hepatic cells, recapitulates key stages of the HBV life cycle, and effectively responds to multiple antiviral drugs. Additionally, McccDNA was observed to more accurately transcribe major viral RNAs than recombinant cccDNAs containing exogenous sequences, and was also able to organize nucleosomes in a sequence-specific manner, resembling those events during natural viral infection. In conclusion, McccDNA generated from single-stranded M13 phage DNA recapitulates key natural properties of HBV cccDNA, and serves as an authentic and promising model to study cccDNA minichromosomes functionality.
2026-03-16 | GSE291625 | GEO