scholarly journals The Arginine-1493 Residue in QRRGRTGR1493G Motif IV of the Hepatitis C Virus NS3 Helicase Domain Is Essential for NS3 Protein Methylation by the Protein Arginine Methyltransferase 1

2001 ◽  
Vol 75 (17) ◽  
pp. 8031-8044 ◽  
Author(s):  
Jaerang Rho ◽  
Seeyoung Choi ◽  
Young Rim Seong ◽  
Joonho Choi ◽  
Dong-Soo Im
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Rna Binding ◽  
Rna Helicase ◽  
Full Length ◽  
Arginine Residue ◽  
Protein Methylation ◽  
Helicase Domain ◽  
Rna Helicases ◽  
Ns3 Protein

ABSTRACT The NS3 protein of hepatitis C virus (HCV) contains protease and RNA helicase activities, both of which are likely to be essential for HCV propagation. An arginine residue present in the arginine-glycine (RG)-rich region of many RNA-binding proteins is posttranslationally methylated by protein arginine methyltransferases (PRMTs). Amino acid sequence analysis revealed that the NS3 protein contains seven RG motifs, including two potential RG motifs in the 1486-QRRGRTGRG-1494 motif IV of the RNA helicase domain, in which arginines are potentially methylated by PRMTs. Indeed, we found that the full-length NS3 protein is arginine methylated in vivo. The full-length NS3 protein and the NS3 RNA helicase domain were methylated by a crude human cell extract. The purified PRMT1 methylated the full-length NS3 and the RNA helicase domain, but not the NS3 protease domain. The NS3 helicase bound specifically and comigrated with PRMT1 in vitro. Mutational analyses indicate that the Arg1493 in the QRR1488GRTGR1493G region of the NS3 RNA helicase is essential for NS3 protein methylation and that Arg1488 is likely methylated. NS3 protein methylation by the PRMT1 was decreased in the presence of homoribopolymers, suggesting that the arginine-rich motif IV is involved in RNA binding. The results suggest that an arginine residue(s) in QRXGRXGR motif IV conserved in the virus-encoded RNA helicases can be posttranslationally methylated by the PRMT1.

scholarly journals Multiple Enzymatic Activities Associated with Recombinant NS3 Protein of Hepatitis C Virus

1998 ◽  
Vol 72 (8) ◽  
pp. 6758-6769 ◽  
Author(s):  
Paola Gallinari ◽  
Debra Brennan ◽  
Chiara Nardi ◽  
Mirko Brunetti ◽  
Licia Tomei ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Synthetic Peptide ◽  
Protease Activity ◽  
Rna Binding ◽  
Rna Helicase ◽  
Enzymatic Activities ◽  
Full Length ◽  
Protease Domain ◽  
Ns3 Protein

ABSTRACT The hepatitis C virus (HCV) nonstructural 3 protein (NS3) contains at least two domains associated with multiple enzymatic activities; a serine protease activity resides in the N-terminal one-third of the protein, whereas RNA helicase activity and RNA-stimulated nucleoside triphosphatase activity are associated with the C-terminal portion. To study the possible mutual influence of these enzymatic activities, a full-length NS3 polypeptide of 67 kDa was expressed as a nonfusion protein in Escherichia coli, purified to homogeneity, and shown to retain all three enzymatic activities. The protease activity of the full-length NS3 was strongly dependent on the activation by a synthetic peptide spanning the central hydrophobic core of the NS4A cofactor. Once complexed with the NS4A-derived peptide, the full-length NS3 protein and the isolated N-terminal protease domain cleaved synthetic peptide substrates with comparable efficiency. We show that, as in the case of the isolated protease domain, the protease activity of full-length NS3 undergoes inhibition by the N-terminal cleavage products of substrate peptides corresponding to the NS4A-NS4B and NS5A-NS5B. We have also characterized and quantified the NS3 ATPase, RNA helicase, and RNA-binding activities under optimized reaction conditions. Compared with the isolated N-terminal and C-terminal domains, recombinant full-length NS3 did not show significant differences in the three enzymatic activities analyzed in independent in vitro assays. We have further explored the possible interdependence of the NS3 N-terminal and C-terminal domains by analyzing the effect of polynucleotides on the modulation of all NS3 enzymatic functions. Our results demonstrated that the observed inhibition of the NS3 proteolytic activity by single-stranded RNA is mediated by direct interaction with the protease domain rather than with the helicase RNA-binding domain.

scholarly journals Structure-Based Mutagenesis Study of Hepatitis C Virus NS3 Helicase

1999 ◽  
Vol 73 (10) ◽  
pp. 8798-8807 ◽  
Author(s):  
Chao Lin ◽  
Joseph L. Kim
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Nucleic Acid ◽  
Atpase Activity ◽  
Rna Binding ◽  
Crystallographic Structure ◽  
Binary Complex ◽  
Helicase Domain ◽  
Wild Type ◽  
Ns3 Protein

ABSTRACT The NS3 protein of hepatitis C virus (HCV) is a bifunctional protein containing a serine protease in the N-terminal one-third, which is stimulated upon binding of the NS4A cofactor, and an RNA helicase in the C-terminal two-thirds. In this study, a C-terminal hexahistidine-tagged helicase domain of the HCV NS3 protein was expressed in Escherichia coli and purified to homogeneity by conventional chromatography. The purified HCV helicase domain has a basal ATPase activity, a polynucleotide-stimulated ATPase activity, and a nucleic acid unwinding activity and binds efficiently to single-stranded polynucleotide. Detailed characterization of the purified HCV helicase domain with regard to all four activities is presented. Recently, we published an X-ray crystallographic structure of a binary complex of the HCV helicase with a (dU)8oligonucleotide, in which several conserved residues of the HCV helicase were shown to be involved in interactions between the HCV helicase and oligonucleotide. Here, site-directed mutagenesis was used to elucidate the roles of these residues in helicase function. Four individual mutations, Thr to Ala at position 269, Thr to Ala at position 411, Trp to Leu at position 501, and Trp to Ala at position 501, produced a severe reduction of RNA binding and completely abolished unwinding activity and stimulation of ATPase activity by poly(U), although the basal ATPase activity (activity in the absence of polynucleotide) of these mutants remained intact. Alanine substitution at Ser-231 or Ser-370 resulted in enzymes that were indistinguishable from wild-type HCV helicase with regard to all four activities. A mutant bearing Phe at Trp-501 showed wild-type levels of basal ATPase, unwinding activity, and single-stranded RNA binding activity. Interestingly, ATPase activity of this mutant became less responsive to stimulation by poly(U) but not to stimulation by other polynucleotides, such as poly(C). Given the conservation of some of these residues in other DNA and RNA helicases, their role in the mechanism of unwinding of double-stranded nucleic acid is discussed.

scholarly journals Structure-Based Mutational Analysis of the Hepatitis C Virus NS3 Helicase

2001 ◽  
Vol 75 (17) ◽  
pp. 8289-8297 ◽  
Author(s):  
Chun-Ling Tai ◽  
Wen-Ching Pan ◽  
Shwu-Huey Liaw ◽  
Ueng-Cheng Yang ◽  
Lih-Hwa Hwang ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Atpase Activity ◽  
Rna Binding ◽  
Mutational Analysis ◽  
Nonstructural Protein ◽  
Rna Helicase ◽  
Helicase Domain ◽  
Helicase Activity ◽  
Conserved Sequence

ABSTRACT The carboxyl terminus of the hepatitis C virus (HCV) nonstructural protein 3 (NS3) possesses ATP-dependent RNA helicase activity. Based on the conserved sequence motifs and the crystal structures of the helicase domain, 17 mutants of the HCV NS3 helicase were generated. The ATP hydrolysis, RNA binding, and RNA unwinding activities of the mutant proteins were examined in vitro to determine the functional role of the mutated residues. The data revealed that Lys-210 in the Walker A motif and Asp-290, Glu-291, and His-293 in the Walker B motif were crucial to ATPase activity and that Thr-322 and Thr-324 in motif III and Arg-461 in motif VI significantly influenced ATPase activity. When the pairing between His-293 and Gln-460, referred to as gatekeepers, was replaced with the Asp-293/His-460 pair, which makes the NS3 helicase more like the DEAD helicase subgroup, ATPase activity was not restored. It thus indicated that the whole microenvironment surrounding the gatekeepers, rather than the residues per se, was important to the enzymatic activities. Arg-461 and Trp-501 are important residues for RNA binding, while Val-432 may only play a coadjutant role. The data demonstrated that RNA helicase activity was possibly abolished by the loss of ATPase activity or by reduced RNA binding activity. Nevertheless, a low threshold level of ATPase activity was found sufficient for helicase activity. Results in this study provide a valuable reference for efforts under way to develop anti-HCV therapeutic drugs targeting NS3.

Crystallization and preliminary X-ray crystallographic analysis of the helicase domain of hepatitis C virus NS3 protein

1998 ◽  
Vol 54 (1) ◽  
pp. 121-123 ◽  
Author(s):  
Lin-Woo Kang ◽  
Hyun-Soo Cho ◽  
Sun-Shin Cha ◽  
Kyung Min Chung ◽  
Sung Hoon Back ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Rna Helicase ◽  
Crystallographic Analysis ◽  
Affinity Column ◽  
Helicase Domain ◽  
Data Set ◽  
Protein Mass ◽  
Terminal Domain ◽  
Ns3 Protein

The NS3 protein of hepatitis C virus (HCV) is thought to be essential for viral replication. The N-terminal domain of the protein contains protease activity and the C-terminal domain contains nucleotide triphosphatase and RNA helicase activity. The RNA helicase domain of HCV NS3 protein was purified by using affinity-column chromatographic methods, and crystallized by using the microbatch crystallization method under oil at 277 K. The crystals belong to primitive trigonal space group P3121 or P3221 with cell dimensions of a = b = 93.3, c = 104.6 Å. The asymmetric unit contains one molecule of the helicase domain, with the crystal volume per protein mass (V m ) of 2.50 Å3 Da−1 and solvent content of about 50.8% by volume. A native data set to 2.3 Å resolution was obtained from a frozen crystal indicating that the crystals are quite suitable for structure determination by multiple isomorphous replacement.

scholarly journals Regulating Intracellular Antiviral Defense and Permissiveness to Hepatitis C Virus RNA Replication through a Cellular RNA Helicase, RIG-I

2005 ◽  
Vol 79 (5) ◽  
pp. 2689-2699 ◽  
Author(s):  
Rhea Sumpter ◽  
Yueh-Ming Loo ◽  
Eileen Foy ◽  
Kui Li ◽  
Mitsutoshi Yoneyama ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Viral Infections ◽  
Cultured Cells ◽  
Rna Replication ◽  
Rna Helicase ◽  
Hcv Rna ◽  
Helicase Domain ◽  
Replication Studies ◽  
Virus Rna

ABSTRACT Virus-responsive signaling pathways that induce alpha/beta interferon production and engage intracellular immune defenses influence the outcome of many viral infections. The processes that trigger these defenses and their effect upon host permissiveness for specific viral pathogens are not well understood. We show that structured hepatitis C virus (HCV) genomic RNA activates interferon regulatory factor 3 (IRF3), thereby inducing interferon in cultured cells. This response is absent in cells selected for permissiveness for HCV RNA replication. Studies including genetic complementation revealed that permissiveness is due to mutational inactivation of RIG-I, an interferon-inducible cellular DExD/H box RNA helicase. Its helicase domain binds HCV RNA and transduces the activation signal for IRF3 by its caspase recruiting domain homolog. RIG-I is thus a pathogen receptor that regulates cellular permissiveness to HCV replication and, as an interferon-responsive gene, may play a key role in interferon-based therapies for the treatment of HCV infection.

Antigenicity of a recombinant NS3 protein representative of ATPase/helicase domain from hepatitis C virus

2003 ◽  
Vol 36 (1) ◽  
pp. 41-49 ◽  
Author(s):  
N Pentón ◽  
A Musacchio ◽  
J.M Rivera ◽  
J Roca ◽  
M Ponce ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Helicase Domain ◽  
Ns3 Protein

scholarly journals Hepatitis C virus NS3 RNA helicase domain with a bound oligonucleotide: the crystal structure provides insights into the mode of unwinding

Structure ◽  
1998 ◽  
Vol 6 (1) ◽  
pp. 89-100 ◽  
Author(s):  
Joseph L Kim ◽  
Kurt A Morgenstern ◽  
James P Griffith ◽  
Maureen D Dwyer ◽  
John A Thomson ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Rna Helicase ◽  
Helicase Domain

scholarly journals Hepatitis C virus NS3 protein interacts with ELKS-δ and ELKS-α, members of a novel protein family involved in intracellular transport and secretory pathways

2005 ◽  
Vol 86 (8) ◽  
pp. 2197-2208 ◽  
Author(s):  
Rachmat Hidajat ◽  
Motoko Nagano-Fujii ◽  
Lin Deng ◽  
Motofumi Tanaka ◽  
Yuki Takigawa ◽  
...  
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Host Cell ◽  
Intracellular Transport ◽  
Terminal Region ◽  
Full Length ◽  
Secretory Pathways ◽  
Cell Functions ◽  
Ns3 Protein ◽  
Enhanced Secretion

The NS3 protein of hepatitis C virus (HCV) has a serine protease activity in its N-terminal region, which plays a crucial role in virus replication. This region has also been reported to interact not only with its viral cofactor NS4A, but also with a number of host-cell proteins, which suggests a multifunctional feature of NS3. By means of yeast two-hybrid screening using an N-terminal region of NS3 as bait, a human cDNA encoding a region of ELKS-δ, a member of a novel family of proteins involved in intracellular transport and secretory pathways, was molecularly cloned. Using co-immunoprecipitation, GST pull-down and confocal and immunoelectron microscopic analyses, it was shown that full-length NS3 interacted physically with full-length ELKS-δ and its splice variant, ELKS-α, both in the absence and presence of NS4A, in cultured human cells, including Huh-7 cells harbouring an HCV subgenomic RNA replicon. The degree of binding to ELKS-δ varied with different sequences of the N-terminal 180 residues of NS3. Interestingly, NS3, either full-length or N-terminal fragments, enhanced secretion of secreted alkaline phosphatase (SEAP) from the cells, and the increase in SEAP secretion correlated well with the degree of binding between NS3 and ELKS-δ. Taken together, these results suggest the possibility that NS3 plays a role in modulating host-cell functions such as intracellular transport and secretion through its binding to ELKS-δ and ELKS-α, which may facilitate the virus life cycle and/or mediate the pathogenesis of HCV.

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