Binding of Nucleolin to HBV cccDNA
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE123715 | GEO | 2021/12/31
REPOSITORIES: GEO
Similar Datasets
Project description:Binding of Nucleolin to HBV cccDNA
| PRJNA509631 | ENA
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: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: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:Nucleolin (NCL) is a major component of the cell nucleolus, which has the ability to rapidly shuttle to several other cell’s compartments. NCL has been shown to play important roles in a variety of essential functions among which ribosome biogenesis, gene expression and cell growth. However, the precise mechanisms underlying NCL functions are still unclear. Our study aimed to provide new information on NCL functions via the identification of its nuclear interacting partners. Using an interactomics approach, we identified 140 binding partners of NCL, among which, a 100 of them, were specifically found associated to NCL independently of the presence of RNA.
2016-04-11 | PXD003554 | Pride
Project description:Hepatitis B Virus (HBV) is a small DNA virus that replicates via an episomal covalently closed circular DNA (cccDNA) that serves as the transcriptional template for viral mRNAs. The host protein, CCCTC-binding factor (CTCF), is a key regulator of cellular transcription by maintaining epigenetic boundaries, nucleosome phasing, stabilisation of long-range chromatin loops and directing alternative exon splicing. We previously reported that CTCF binds two conserved motifs within Enhancer I of the HBV genome and represses viral transcripts, however, the underlying mechanisms were not identified. We show that CTCF depletion in cells harbouring cccDNA-like HBV molecules and in de novo infected cells resulted in an increase in spliced transcripts, which was most notable in the abundant SP1 spliced transcript. In contrast, depletion of CTCF in cell lines with integrated HBV DNA had no effect on the abundance of viral transcripts and in line with this observation there was limited evidence for CTCF binding to viral integrants, suggesting that CTCF-regulation of HBV transcription is specific to episomal cccDNA. Analysis of HBV chromatin topology by Assay for Transposase Accessibility/sequencing (ATAC-Seq) revealed an accessible region spanning Enhancers I and II and the basal core promoter (BCP). Mutating the CTCF binding sites within Enhancer I resulted in a dramatic rearrangement of chromatin accessibility where the open chromatin region was no longer detected, indicating loss of the phased nucleosome up- and down- stream of the HBV enhancer/BCP. These data demonstrate that CTCF functions to regulate HBV chromatin conformation and nucleosomal positioning in episomal maintained cccDNA, which has important consequences for HBV transcription regulation.
2024-01-18 | GSE249278 | GEO
Project description:Hepatitis B Virus (HBV) is a small DNA virus that replicates via an episomal covalently closed circular DNA (cccDNA) that serves as the transcriptional template for viral mRNAs. The host protein, CCCTC-binding factor (CTCF), is a key regulator of cellular transcription by maintaining epigenetic boundaries, nucleosome phasing, stabilisation of long-range chromatin loops and directing alternative exon splicing. We previously reported that CTCF binds two conserved motifs within Enhancer I of the HBV genome and represses viral transcripts, however, the underlying mechanisms were not identified. We show that CTCF depletion in cells harbouring cccDNA-like HBV molecules and in de novo infected cells resulted in an increase in spliced transcripts, which was most notable in the abundant SP1 spliced transcript. In contrast, depletion of CTCF in cell lines with integrated HBV DNA had no effect on the abundance of viral transcripts and in line with this observation there was limited evidence for CTCF binding to viral integrants, suggesting that CTCF-regulation of HBV transcription is specific to episomal cccDNA. Analysis of HBV chromatin topology by Assay for Transposase Accessibility/sequencing (ATAC-Seq) revealed an accessible region spanning Enhancers I and II and the basal core promoter (BCP). Mutating the CTCF binding sites within Enhancer I resulted in a dramatic rearrangement of chromatin accessibility where the open chromatin region was no longer detected, indicating loss of the phased nucleosome up- and down- stream of the HBV enhancer/BCP. These data demonstrate that CTCF functions to regulate HBV chromatin conformation and nucleosomal positioning in episomal maintained cccDNA, which has important consequences for HBV transcription regulation.
2024-01-18 | GSE248738 | GEO
Project description:Hepatitis B virus (HBV) persists by depositing a covalently closed circular DNA (cccDNA) in the nucleus that cannot be targeted by available antivirals. Cytokine treatments can purge cccDNA from the nucleus of infected cells by APOBEC3-mediated deamination. cccDNA levels in HBV-infected cells were not reduced by overexpression of APOBEC3A alone, but only after simultaneous addition of interferon. This indicated the need of an additional, interferon-induced factor (ISG). Microarray analysis identified ISG20 as the only nuclease located to the nucleus induced by type I and II interferons. ISG20 was confirmed to be expressed in acute, self-limiting but not in chronic hepatitis B in human livers. ISG20 knockdown abolished the interferon-induced loss of cccDNA, and co-expression of ISG20 and APOBEC3A was sufficient to diminish cccDNA without further treatment. To conclude, nucleolar ISG20 was identified as the nuclease contributing to interferon-induced purging of HBV cccDNA, opening new avenues for antiviral targeting.
2020-07-22 | GSE134929 | GEO
Project description:In search for nuclear partners of initiator-tRNA, previously shown to be involved in a quality control of splice site selection, we identified nucleolin (NCL) as specifically and directly bound to it in the nucleus and not in the cytoplasm (using affinity purification of UV crosslinked nuclear initiator-tRNA followed by mass spectrometry). To further explore the role of NCL in splice site selection, we knocked down NCL. We report the activation of 399 latent splice sites upon NCL knockdown, as revealed by RNA deep sequencing of siRNA treated NCL compared to control siRNA. Our study identifies NCL as the first protein component of this quality control mechanism of splice site selection. Our study thus establishes an experimental strategy and computational pipeline that could be used to identify other components of this quality control mechanism.
2022-03-08 | GSE142836 | GEO