Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0019163 (hepatitis B)
 38,309 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The posttranscriptional regulatory element (PRE) of hepatitis B virus is an RNA element important for the export of viral mRNA from the nucleus to the cytoplasm. The cellular export pathway utilized by the PRE is controversial. We present data showing that PRE-dependent export is blocked by vesicular stomatitis virus matrix protein, an inhibitor of all cellular RNA export other than tRNA export. It is also blocked by a mutated form of Ran-binding protein 1, which blocks export mediated by the human immunodeficiency virus Rev and Rev-response element (RRE) but not export mediated by the simian retrovirus constitutive transport element (CTE). On the other hand, PRE-dependent export is not blocked by either TAgRex or leptomycin B, two agents that prevent Rev/RRE-mediated export. Therefore, PRE appears to utilize an export pathway different from that of Rev/RRE or CTE.
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PMID:Distinct export pathway utilized by the hepatitis B virus posttranscriptional regulatory element. 1038 54

Core particles of hepatitis B virus (HBV) are able to improve the immunogenicity of foreign sequences exposed on the particle surface. The insertion site in the core antigen of HBV (HBcAg) determines the surface presentation and thus the immunogenicity of the foreign sequence. For direct comparison of the value of potential insertion sites in the core antigen, we constructed vectors allowing insertions of a model marker epitope DPAFR. This epitope was inserted at the N-terminus, the c/e1 loop, behind amino acid (aa) 144 and behind aa 183 (DPAF only). In addition, we generated a mosaic construct allowing the co-expression of HBcAg and a HBcAg/DPAFR fusion protein due to a suppressor tRNA-mediated readthrough mechanism. All 6 constructs allowed the formation of chimaeric or mosaic core-like particles. Western blot analyses and a direct ELISA demonstrated the presence of the DPAFR sequence in the chimaeric and mosaic particles. Competitive ELISA and immune electron-microscopic data suggested the c/e1 loop as the insertion site of choice for presenting foreign sequences on the surface of chimaeric HBV core particles. However, the N-terminal fusion also allowed partial surface exposure of the DPAFR motif. In contrast, in particles of constructs carrying the DPAFR insert at aa position 144 or 183, respectively, the epitope seemed not to be surface accessible.
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PMID:Characterization of potential insertion sites in the core antigen of hepatitis B virus by the use of a short-sized model epitope. 1039 4

Circumstantial evidence suggests that the secreted hepatitis B virus (HBV) e antigen (HBeAg) and/or its 22 kDa precursor (P22) have an essential role in the establishment of persistent infection. In order to identify cellular proteins that could interact with P22, large amounts of this protein are required to perform pull-down assays. A plasmid was constructed encoding a recombinant P22 with a Histidine-tag at its N-terminal extremity (P22r). The initial attempts to overexpress P22r in a conventional Escherichia coli strain failed, most likely due to the presence of rare AGA/AGG codon clusters in the 3' part of the gene. To overcome this difficulty, P22r was overexpressed in the Epicurian coli BL21-codonplus (DE3)-RIL strain, which possesses extra copies of the ArgU gene that encodes the tRNA(AGA/AGG). In this strain, P22r was overexpressed successfully and then purified in milligram quantities by metal affinity chromatography on Ni2+-chelated His-Bind resin. The purified recombinant protein P22r was able to interact with a cellular protein (P32), which had previously been shown to co-immunoprecipitate with native P22, indicating that at least some of the P22r molecules were folded correctly.
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PMID:Overexpression and purification of the hepatitis B e antigen precursor. 1190 34

Recently we have shown that the substrate specificity of catalytic IgG isolated from sera of patients with Hashimoto's thyroiditis, systemic lupus erythematosus (SLE), polyarthritis and hepatitis B for classic poly(N) homopolynucleotide substrates and for specific tRNA(Phe) with compact and stable structure was correlated with the type of disease. At the same time the cleavage specificity was different in comparison with that of all known human RNases. Here we investigated for the first time the hydrolysis by the IgGs isolated from sera of 31 patients with different diseases of the in vitro transcript of human mitochondrial tRNA(Lys) which has less stable structure as compared to tRNA(Phe). The level of activity was strongly dependent on the patient, but in general increased in the order: hepatitis B </= Hashimoto's thyroiditis < SLE. The pH dependencies and various salts effects also varied for Abs from the sera of different patients. Nevertheless, the RNase activity of all IgGs was specifically stimulated by Mg(2+) ions, that essentially completely suppress the activity of all known human RNases. In contrast to the classical substrates, no correlation between patient's IgG cleavage specificity and a specific disease was revealed; each patient demonstrated an individual repertoire of polyclonal RNA-hydrolyzing IgGs independently of the disease.
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PMID:Variability of Substrate Specificity of Serum Antibodies Obtained from Patients with Different Autoimmune and Viral Diseases in Reaction of tRNA Hydrolysis. 1268 13

The core antigen (HBcAg) of hepatitis B Virus (HBV) can be expressed in Escherichia coil where it assembles into icosahedral particles containing 240 or 180 subunits. Analysis of the two kinds of particles by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) showed that a substantial proportion of their subunits were smaller than the full-length HBcAg monomer and of variable size, but all had the same N-terminal sequence showing that the smaller species were heterogeneous in their arginine-rich C-terminal regions. Around 50% of these arginine residues are encoded by the triplet AGA which is rare in E. coli. Supplementation of the level of AGA tRNA in the cell by transformation with plasmids expressing the T4 AGA tRNA gene significantly enhanced the yield of HBcAg. Fusion phage carrying a ligand specific for HBcAg showed no significant difference in the affinity for the two sizes of HBcAg particles, but in similar reactions in solution HBV surface antigen exhibited differential affinities for the same two HBcAg preparations.
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PMID:Hepatitis B virus core antigen: enhancement of its production in Escherichia coli, and interaction of the core particles with the viral surface antigen. 1271 87

In this article, the immunogenicity of tRNA and the recognition of tRNA by Toll-like receptors (TLRs) are analyzed. Analyses of the effects of different tRNA(Ala)(UGC) fragments (tRNA(Ala)1-76 [corresponding to positions 1 through 76], tRNA(Ala)26-76, tRNA(Ala)40-76, tRNA(Ala)62-76, tRNA(Ala)1-70, tRNA(Ala)26-70, tRNA(Ala)40-70, and tRNA(Ala)62-70) on the immune responses of hepatitis B surface antigen (HBsAg) were performed with BALB/c mice. Results show that tRNA(Ala)1-76, tRNA(Ala)26-76, tRNA(Ala)40-76, and tRNA(Ala)62-76 adjuvants not only induced stronger T helper (Th) 1 immune responses but also cytotoxic-T-lymphocyte (CTL) responses relative to tRNA(Ala)1-70, tRNA(Ala)26-70, tRNA(Ala)40-70, and tRNA(Ala)62-70 adjuvants in HBsAg immunization. A deletion of the D loop (tRNA(Ala)26-76), anticodon loop (tRNA(Ala)40-76), or TpsiC (tRNA(Ala)62-76) loop of tRNA(Ala)(UGC) does not significantly decrease the adjuvant characteristic of tRNA(Ala)(UGC). However a deletion of the 3'-end CCACCA sequence (tRNA(Ala)1-70, tRNA(Ala)26-70, tRNA(Ala)40-70, and tRNA(Ala)62-70) of tRNA(Ala)(UGC) significantly decreased the adjuvant characteristic in Th1 and CTL immune responses. Moreover, the recognitions of different tRNA(Ala)(UGC) fragments by TLR3, TLR7, TLR8, and TLR9 were analyzed. Results show that a deletion of the 3' CCACCA sequence of tRNA(Ala)(UGC) significantly decreased the recognition by TLR3. We concluded that the 3' CCACCA sequence of tRNA(Ala)(UGC) is the important motif to induce Th1 and CTL responses and this motif can be effectively recognized by TLR3.
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PMID:The 3' CCACCA sequence of tRNAAla(UGC) is the motif that is important in inducing Th1-like immune response, and this motif can be recognized by Toll-like receptor 3. 1682 9

In Escherichia coli the rare codons AGG, AGA and CGA are reported to have a detrimental effect on protein synthesis, especially during the expression of heterologous proteins. In the present work, we have studied the impact of successive clusters of these rare codons on the accuracy of mRNA translation in E. coli. For this purpose, we have analyzed the expression of an mRNA which contains in its 3' region a triplet and a tandem of AGA codons. This mRNA is derived from the human hepatitis B virus (HBV) preC gene. Both in eukaryotic cells and in eukaryotic cell-free translation system, this mRNA, directs the synthesis of a single 25 kDa protein. However, in a conventional E. coli strain BL 21 (DE3), transformed with a plasmid expressing this protein the synthesis of four polypeptides ranging from 30 to 21.5 kDa can be observed. Using different approaches, notably expression of i) precore mutated proteins or ii) chimeric proteins containing HA- and Myc-tags downstream of the AGA clusters (respectively in the -1 or +1 frame), we have found that when the ribosome encounters the AGA clusters, it can then resume the translation in both +1 and -1 frames. This result is in agreement with the model proposed recently by Baranov et al. (Baranov, P.V., Gesteland, R.F., Atkins, J.F., 2004. P-site tRNA is a crucial initiator of ribosomal frameshifting. RNA 10, 221-230), thus confirming that AGA/AGG codons can serve as sites for -1 frameshifting events. Only +1 frameshifting was suggested previously to occur at the AGA/AGG clusters.
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PMID:Ribosome can resume the translation in both +1 or -1 frames after encountering an AGA cluster in Escherichia coli. 1831 65

Using exogenous sequences to express RNA interference (RNAi) activators has potential for the treatment of chronic viral infections. However, availability of a variety of suitable of promoter elements is important to optimize transcription control of silencing sequences and facilitate multitargeting. Recent demonstration that tRNA miR genes occur naturally has prompted investigating the incorporation these tRNA Pol III promoters into exogenous RNAi-activating cassettes. We have assessed efficacy of Pol III tRNA(Lys3) short hairpin RNA (shRNA) sequences that target hepatitis B virus (HBV). These cassettes achieved good silencing at low concentrations, and efficacy compared favorably to that of equivalent U6, H1 and CMV expression cassettes. HBV replication in cell culture was inhibited and northern blot hybridization analysis confirmed processing of the tRNA(Lys3) transcripts to form intended antiviral guide sequences. Importantly effects were observed without evidence of disruption of endogenous miR function. Analysis in a murine hydrodynamic injection model of HBV replication confirmed that the tRNA(Lys3) expression cassettes are also effective in vivo. Usefulness of tRNA(Lys3) antiviral expression cassettes expands the repertoire of promoters available for RNAi-mediated HBV silencing and advances the application of expressed sequences for therapeutic gene silencing.
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PMID:tRNA Lys3 promoter cassettes that efficiently express RNAi-activating antihepatitis B virus short hairpin RNAs. 2059 52

External guide sequences (EGSs) are RNA molecules that consist of a sequence complementary to a target mRNA and recruit intracellular ribonuclease P (RNase P), a tRNA processing enzyme, for specific degradation of the target mRNA. We have previously used an in vitro selection procedure to generate EGS variants that efficiently induce human RNase P to cleave a target mRNA in vitro. In this study, we constructed EGSs from a variant to target the overlapping region of the S mRNA, pre-S/L mRNA, and pregenomic RNA (pgRNA) of hepatitis B virus (HBV), which are essential for viral replication and infection. The EGS variant was about 50-fold more efficient in inducing human RNase P to cleave the mRNA in vitro than the EGS derived from a natural tRNA. Following Salmonella-mediated gene delivery, the EGSs were expressed in cultured HBV-carrying cells. A reduction of about 97% and 75% in the level of HBV RNAs and proteins and an inhibition of about 6,000- and 130-fold in the levels of capsid-associated HBV DNA were observed in cells treated with Salmonella vectors carrying the expression cassette for the variant and the tRNA-derived EGS, respectively. Our study provides direct evidence that the EGS variant is more effective in blocking HBV gene expression and DNA replication than the tRNA-derived EGS. Furthermore, these results demonstrate the feasibility of developing Salmonella-mediated gene delivery of highly active EGS RNA variants as a novel approach for gene-targeting applications such as anti-HBV therapy.
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PMID:Engineered external guide sequences are highly effective in inhibiting gene expression and replication of hepatitis B virus in cultured cells. 2377 59

Persistent infections with hepatitis B virus (HBV) or hepatitis C virus (HCV) account for the majority of cases of hepatic cirrhosis and hepatocellular carcinoma (HCC) worldwide. Small, non-coding RNAs play important roles in virus-host interactions. We used high throughput sequencing to conduct an unbiased profiling of small (14-40 nts) RNAs in liver from Japanese subjects with advanced hepatitis B or C and hepatocellular carcinoma (HCC). Small RNAs derived from tRNAs, specifically 30-35 nucleotide-long 5' tRNA-halves (5' tRHs), were abundant in non-malignant liver and significantly increased in humans and chimpanzees with chronic viral hepatitis. 5' tRH abundance exceeded microRNA abundance in most infected non-cancerous tissues. In contrast, in matched cancer tissue, 5' tRH abundance was reduced, and relative abundance of individual 5' tRHs was altered. In hepatitis B-associated HCC, 5' tRH abundance correlated with expression of the tRNA-cleaving ribonuclease, angiogenin. These results demonstrate that tRHs are the most abundant small RNAs in chronically infected liver and that their abundance is altered in liver cancer.
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PMID:Small tRNA-derived RNAs are increased and more abundant than microRNAs in chronic hepatitis B and C. 2556 97


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