Disease relevance of HCVgp1

• Hepatitis C virus encodes a large polyprotein precursor that is proteolytically processed into at least 10 distinct products, in the order NH2-C-E1-E2-p7-NS2-NS3-NS4A-NS4B-NS5A-NS5B -COOH [1].
• To investigate whether other viral gene products may be involved in this interaction, we constructed an HCV cDNA expression library in bacteriophage T7 allowing portions of the HCV polyprotein to be displayed on the phage surface [2].
• Hepatic iron overload induces hepatocellular carcinoma in transgenic mice expressing the hepatitis C virus polyprotein [3].
• CONCLUSIONS: Iron overload induces mitochondrial injury and increases the risk of HCC development in transgenic mice expressing the HCV polyprotein [3].
• The virus has a positive-sense RNA genome encoding a single polyprotein with the virion components located in the N-terminal portion [4].

High impact information on HCVgp1

• During replication of hepatitis C virus (HCV), the final steps of polyprotein processing are performed by a viral proteinase located in the N-terminal one-third of nonstructural protein 3 [5].
• A serine protease located within the HCV NS3 protein processes the viral polyprotein at four specific sites and is considered essential for replication [6].
• To determine if immunologically driven sequence variation occurs with HCV persistence, we coordinately analyzed sequence evolution and CD8+ T cell responses to epitopes covering the entire HCV polyprotein in subjects who were followed prospectively from before infection to beyond the first year [7].
• METHODS: Transgenic C57BL/6 mice with liver-specific expression of RNA encoding the complete viral polyprotein (FL-N transgene) or viral structural proteins (S-N transgene) were compared with nontransgenic littermates for altered liver morphology and function [8].
• During biosynthesis of the polyprotein, an internal signal sequence between the core protein and the envelope protein E1 targets the nascent polypeptide to the endoplasmic reticulum (ER) membrane for translocation of E1 into the ER [4].

Chemical compound and disease context of HCVgp1

• The hepatitis C virus (HCV) NS3 protein contains a serine proteinase domain implicated in the maturation of the viral polyprotein [9].
• The nonstructural protein 3 (NS3) of hepatitis C virus (HCV) inhibits the nuclear transport and the enzymatic activity of the catalytic subunit of protein kinase A. This inhibition is mediated by an arginine-rich domain localized between amino acids 1487-1500 of the HCV polyprotein [10].
• In the present study, the capacity of hepatitis C virus (HCV) proteins to elicit intracellular membrane alterations was investigated by expressing, in tetracycline-regulated cell lines, a comprehensive panel of HCV proteins individually as well as in the context of the entire HCV polyprotein [11].
• Using as substrates a series of chimeric proteins containing various fragments of the hepatitis C virus precursor polyprotein between Escherichia coli maltose binding protein and dihydrofolate reductase, we analyzed the substrate requirements of hepatitis C viral serine proteinase (Cpro-2) for intermolecular polypeptide cleavage in E. coli [12].
• The solid phase synthesis of a set of peptide aldehydes derived from the NS5A/NS5B junction of hepatitis C virus (HCV) viral polyprotein is demonstrated using an oxazolidine linker and the Multipin method [13].

Biological context of HCVgp1

• In this study, we demonstrate that TGF-beta-mediated transactivation is decreased in cells exogenously expressing the intact HCV polyprotein [14].
• The HCV genome is a plus-stranded RNA that encodes a single polyprotein processed into at least 10 mature polypeptides [15].
• Translation of the hepatitis C virus (HCV) polyprotein is mediated by an internal ribosome entry site (IRES) that is located mainly within the 5' non-translated region of the viral genome [16].
• This protein, which we named the F protein, is synthesized from the initiation codon of the polyprotein sequence followed by ribosomal frameshift into the -2/+1 reading frame [17].
• The sequence (9379 nucleotides) has a single large open reading frame that could encode a viral polyprotein precursor of 3011 amino acids [18].

Anatomical context of HCVgp1

• This triple decoding function does not require sequences flanking the frameshift signal and is apparently independent of membranes and the synthesis of the HCV polyprotein [19].
• Impaired clearance of virus-infected hepatocytes in transgenic mice expressing the hepatitis C virus polyprotein [20].
• By using a plasmid-based transient protein expression system in cultured cells and an in vitro transcription/translation system, we analyzed the proteolytic processing of the putative nonstructural protein region of the precursor polyprotein from a Japanese type of hepatitis C virus [21].
• Importantly, a comparable inhibition of AP1 reporter activity was observed in hepatocyte-derived cell lines transduced with a baculovirus vector driving expression of full-length HCV polyprotein [22].
• A transient protein expression system in COS-1 cells was used to study the role of hepatitis C virus (HCV)-encoded NS4A protein on HCV nonstructural polyprotein processing [23].

Associations of HCVgp1 with chemical compounds

• The serine protease activity is required for proteolytic processing at the NS3-NS4A, NS4A-NS4B, NS4B-NS5A, and NS5A-NS5B polyprotein cleavage sites [24].
• Arginine 467 in the helicase domain of NS3 (arginine 1493 in the polyprotein) can be methylated by protein arginine methyltransferase 1 (PRMT1) [25].
• The HCV polyprotein contains a hypervariable region (HVR1) located at the N terminus of the second envelope glycoprotein E2 [26].
• The immunogenicity of this polyprotein, which was formulated in alum, oil-in-water emulsion MF59 or poly(dl-lactide co-glycolide) in the presence or absence of CpG adjuvant, was then determined in a murine model for induction of B- and T-cell responses [27].
• Expression of the E1E2 polyprotein, even when preceded by GST, led to processing in insect cells and detection of an E1E2 complex that could be specifically purified by glutathione affinity chromatography [28].

Analytical, diagnostic and therapeutic context of HCVgp1

• Sequence analysis of these and 16 additional full-length clones revealed that seven clones were defective for polyprotein synthesis, and the remaining nine clones had 6-28 amino acid mutations in the predicted polyprotein compared with the consensus sequence of H77 [29].
• By double label immunofluorescence analyses, NS5B was found in the endoplasmic reticulum (ER) or an ER-like modified compartment both when expressed alone or in the context of the entire HCV polyprotein [30].
• Following in vitro stimulation of PBMC, HCV-specific cell cultures from each subject were screened with an overlapping panel of synthetic 20-mer peptides spanning the entire HCV polyprotein [31].
• Indirect immunofluorescence experiments showed that core proteins C173 and C191, when produced from HCV full-length protein or various polyprotein precursors, displayed a cytoplasmic localization [32].
• To examine the effect of the HCV-specific CTL response in patients with chronic hepatitis C on viral load and disease activity, we quantitated the strength of the multispecific CTL response against 10 independent epitopes within the HCV polyprotein [33].

References