Project description:Background and Aims Chronic infection with hepatitis B virus (HBV) has been known to cause liver cirrhosis and hepatocellular carcinoma. Although nucleos(t)ide analogs are mainly used for the treatment of HBV, they require long-term administration and may lead to the emergence of drug resistance. Therefore, to identify targets for the development of novel anti-HBV therapies, we screened HBV-suppressive host factors using RNA-bnding protein (RBP) expression plasmids library. Approach and Results We screened the RBP library by generating overexpressing RBP cell lines and observing anti-HBV effect. As a result, we identified NEDD4-binding protein 1 (N4BP1) as a candidate showing anti-HBV effect. In hepatocellular carcinoma cell lines, overexpression of N4BP1 decreased the relaxed circular DNA (rcDNA) levels, while suppression of N4BP1 expression increased rcDNA levels. Restoring N4BP1 expression in N4BP1 knockout cells regained the anti-HBV effect of N4BP1. Next, we constructed KH-like and RNase domain-deficient mutants of N4BP1 and examined their effects on HBV replication, and found that both the KH-like and RNase domains are required for its anti-HBV effect. N4BP1 suppresses the step where pregenomic RNA (pgRNA) is synthesized in the HBV life cycle by promoting degradation of pgRNA. Transcriptome analyses of primary human hepatocytes overexpressing N4BP1 suggested that N4BP1 may have anti-HBV activity independent of other host factors. Conclusions In summary, N4BP1 was found to be a novel anti-HBV factor. N4BP1 inhibited HBV replication by promoting pgRNA degradation.
Project description:Certain organs are capable of containing the replication of various types of viruses. In the liver, infection of Hepatitis B virus (HBV), the etiological factor of Hepatitis B and hepatocellular carcinoma (HCC), often remains asymptomatic and leads to a chronic carrier state. Here we investigated how hepatocytes contain HBV replication and promote their own survival by orchestrating a translational defense mechanism via the stress-sensitive SUMO-2/3-specific peptidase SENP3. We found that SENP3 expression level decreased in HBV-infected hepatocytes in various models including HepG2-NTCP cell lines and a humanized mouse model. Downregulation of SENP3 reduced HBV replication and boosted host protein translation. We also discovered that IQGAP2, a Ras GTPase-activating-like protein, is a key substrate for SENP3-mediated de-SUMOylation. Downregulation of SENP3 in HBV infected cells facilitated IQGAP2 SUMOylation and degradation, which leads to suppression of HBV gene expression and restoration of global translation of host genes via modulation of AKT phosphorylation. Thus, The SENP3-IQGAP2 de-SUMOylation axis is a host defense mechanism of hepatocytes that restores host protein translation and suppresses HBV gene expression.
Project description:Programmed mutagenesis of the immunoglobulin locus of B-lymphocytes during class switch recombination and somatic hypermutation requires RNA polymerase II (RNA polII) transcription complex dependent targeting of the DNA mutator, Activation Induced cytidine Deaminase (AID). AID deaminates cytidine residues on substrate sequences in the immunoglobulin (Ig) locus via a transcription-dependent mechanism and this activity is stimulated by the RNA polII stalling co-factor Spt5 and the eleven-subunit cellular non-coding RNA 3’-5’ exonucleolytic processing complex, RNA exosome. The mechanism by which the RNA exosome recognizes immunoglobulin locus RNA substrates to stimulate AID DNA deamination activity on its in vivo substrate sequences is an important question. Here we report that E3-ubiquitin ligase Nedd4 destabilizes AID-associated RNA polII by a ubiquitination event leading to generation of 3’-end free RNA exosome RNA substrates at the Ig locus and other AID target sequences genome-wide. Using highthrough-out RNA sequencing technology, we find that lack of Nedd4 activity in B cells leads to accumulation of RNA exosome substrates at AID target genes. Moreover, we find that Nedd4-deficient B cells are inefficient in undergoing class switch recombination. Taken together, our study links non-coding RNA processing following RNA polymerase II pausing with regulation of the mutator AID protein. Our study also identifies Nedd4 as a regulator of non-coding RNA that are generated by stalled RNA polII genome-wide. Splenic B cells from Nedd4+/+ and Nedd4-/- B cells fetal liver chimeric mice were were stimulated in culture for IgG1 CSR. Total RNA was isolated and evaluated with whole genome RNA-seq
Project description:This study aimed to better characterize the repertoire of serum HBV RNAs during chronic HBV infection in humans, which remains understudied. Using RT-PCR, qPCR, RNA-sequencing and immuno-precipitation, we found that (i) >50% of serum samples bore different amounts of HBV replication-derived RNAs (rd-RNAs); (ii) a few samples contained RNAs transcribed from integrated HBV DNA including 5'-HBV-human-3' RNAs (integrant-derived RNAs or id-RNAs) and 5'-human-HBV-3' transcripts as a minority of serum HBV RNAs; (iii) spliced HBV RNAs were abundant in <50% of analyzed samples; (iv) most serum rd-RNAs were polyadenylated via conventional HBV polyadenylation signal; (v) pre-genomic RNA (pgRNA) was the major component of the pool of serum RNAs; (vi) area of HBV positions 1531-1739 had very high RNA reads coverage and thus should be used as a target for detecting serum HBV RNAs; (vii) vast majority of rd-RNAs and pgRNA were associated with HBV virions, but not with unenveloped capsids, exosomes, classic microvesicles or apoptotic vesicles and bodies; (viii) considerable rd-RNAs presence in the circulating immune complexes was found in a few samples; and (ix) serum rcDNA and rd-RNAs should be quantified simultaneously to evaluate HBV replication status and efficacy of anti-HBV therapy with nucleos(t)ide analogs. In summary, sera contain various HBV RNA types of different origin, which are likely secreted via different mechanisms. In addition, since we previously showed that id-RNAs were abundant or predominant HBV RNAs in many of liver and hepatocellular carcinoma tissues comparing to rd-RNAs, there is likely a mechanism favoring the egress of the replication-derived RNAs.
Project description:RNA chemical modifications have been found to play important biological functions. Among which, the 5-methylcytosine (m5C) modification has been reported to participate in viral replication through affecting RNA processing, such as export, decay, translation and so on. In this study, we performed bisulfite sequencing (BS-seq) on HBV 1.1-mer-transfected huh7 cells to identify the m5C sites in HBV mRNA and their function in virus replication was verified. To investigate the mechanism by which m5C methyltransferase NSUN2 suppresses HBV replication, altered global m5C levels in host genes in HBV 1.1-mer-transfected cells were examined by BS-seq. We found that the m5C modification of genes associated with antiviral immunity changed significantly after viral infection. Our study provide new molecular insights into the mechanism of HBV-mediated IFN inhibition
Project description:In the study, we identified protein arginine methyltransferase 5 (PRMT5) as a novel restriction factor of HBV replication. We have also demonstrated that PRMT5 can interact with the HBV core and methylate its arginine residues within arginine-rich domain. We identified two types of HBc post-translational modifications: arginine methylation and ubiquitination. While monomethylated HBc retains cytoplasmic localization, symmetric dimethylation is linked to serine phosphorylation and nuclear transport. Thus arginine methylation and ubiquitination are novel types of HBc post-translational modifications which add another level of complexity to the understanding of HBc function and regulation of HBV replication
Project description:Acetaminophen (APAP) overdose provokes various degrees of liver injury, whose pathogenesis involves multiple pathological events, such as mitochondrial damage and necrosis. E3 ubiquitin ligase neural precursor cell expressed developmentally downregulated 4-1 (NEDD4-1) plays vital roles in regulating a wide spectrum of physiological processes, and has been implicated in the pathogenesis of numerous liver disease. However, studies about the regulation of NEDD4-1 on APAP-induced liver injury (AILI) is still deficient. Thus, the aim of this study is to determine whether and how NEDD4-1 plays a role in AILI. Thus, we performed transcriptomic studies comparing liver samples of APAP-treated Flox or APAP-treated hepatocyte-specific Nedd4-1 (HepKO) deficiency mice,
Project description:Five matching sets of non-malignant liver tissues and HCCs from individuals chronically infected with hepatitis B virus (HBV) were examined. The HBV genomic sequences were determined using overlapping PCR amplicons covering the entire viral genome. Four pairs of tissues were infected with HBV of genotype C, while one pair - with genotype B. HBV replication markers were found in all tissues. In majority of HCC samples, the levels of pre-genomic/pre-core RNA (pgRNA) and covalently closed circular DNA (cccDNA) were lower than those of liver tissue counterparts. Regardless of the presence of HBV replication markers, (i) integrant-derived HBV RNAs (id-RNAs) were found using RT-PCR analysis in all tissues, and were considerably abundant or predominant in 6/10 tissue samples (2 livers and 4 HCCs); (ii) the RNAs that were polyadenylated using cryptic HBV polyadenylation signal and therefore could be produced by HBV replication or derived from integrated HBV DNA were found in 5/10 samples (3 livers and 2 HCCs), and were considerably abundant species in 3/10 tissues (2 livers and 1 HCC); and (iii) cccDNA-transcribed RNAs polyadenylated near position 1931 were not abundant in 7/10 tissues (2 livers and 5 HCCs), and were predominant only in two livers. Subsequent RNA sequencing analysis of selected liver/HCC samples also showed relative abundance of id-RNAs in most of examined tissues. Our findings suggesting that id-RNAs could represent a significant source of HBV envelope proteins, which is independent of viral replication, are discussed in the context of possible contribution of id-RNAs to the HBV life cycle.
Project description:Nedd4 is an E3 ubiquitin ligase that has essential roles in neural crest cell development. This study aimed to detect the gene expression changes induced by removing Nedd4 in the neural crest cell line, NCU10K, to define the molecular pathways regulated by Nedd4.