The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Michael M.c. Lai - One of the best experts on this subject based on the ideXlab platform.
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modification of small Hepatitis Delta virus Antigen by sumo protein
Journal of Virology, 2010Co-Authors: Chung-hsin Tseng, King-song Jeng, Taishan Cheng, Chiungyueh Shu, Michael M.c. LaiAbstract:Hepatitis Delta Antigen (HDAg) is a nuclear protein that is intimately involved in Hepatitis Delta virus (HDV) RNA replication. HDAg consists of two protein species, the small form (S-HDAg) and the large form (L-HDAg). Previous studies have shown that posttranslational modifications of S-HDAg, such as phosphorylation, acetylation, and methylation, can modulate HDV RNA replication. In this study, we show that S-HDAg is a small ubiquitin-like modifier 1 (SUMO1) target protein. Mapping data showed that multiple lysine residues are SUMO1 acceptors within S-HDAg. Using a genetic fusion strategy, we found that conjugation of SUMO1 to S-HDAg selectively enhanced HDV genomic RNA and mRNA synthesis but not Antigenomic RNA synthesis. This result supports our previous proposition that the cellular machinery involved in the synthesis of HDV Antigenomic RNA is different from that for genomic RNA synthesis and mRNA transcription, requiring different modified forms of S-HDAg. Sumoylation represents a new type of modification for HDAg.
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Hepatitis Delta virus RNA replication.
Viruses, 2009Co-Authors: Chung-hsin Tseng, Michael M.c. LaiAbstract:Hepatitis Delta virus (HDV) is a distant relative of plant viroids in the animal world. Similar to plant viroids, HDV replicates its circular RNA genome using a double rolling-circle mechanism. Nevertheless, the production of Hepatitis Delta Antigen (HDAg), which is indispensible for HDV replication, is a unique feature distinct from plant viroids, which do not encode any protein. Here the HDV RNA replication cycle is reviewed, with emphasis on the function of HDAg in modulating RNA replication and the nature of the enzyme involved.
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Transcription of Subgenomic mRNA of Hepatitis Delta Virus Requires a Modified Hepatitis Delta Antigen That Is Distinct from Antigenomic RNA Synthesis
Journal of virology, 2008Co-Authors: Chung-hsin Tseng, King-song Jeng, Michael M.c. LaiAbstract:Hepatitis Delta virus (HDV) contains a viroid-like, 1.7-kb circular RNA genome, which replicates via a double-rolling-circle model. However, the exact mechanism involved in HDV genome RNA replication and subgenomic mRNA transcription is still unclear. Our previous studies have shown that the replications of genomic and Antigenomic HDV RNA strands have different sensitivities to alpha-amanitin and are associated with different nuclear bodies, suggesting that these two strands are synthesized in different transcription machineries in the cells. In this study, we developed a unique quantitative reverse transcription-PCR (qRT-PCR) procedure for detection of various HDV RNA species from an RNA transfection system. Using this qRT-PCR procedure and a series of HDV mutants, we demonstrated that Arg-13 methylation, Lys-72 acetylation, and Ser-177 phosphorylation of small Hepatitis Delta Antigen (S-HDAg) are important for HDV mRNA transcription. In addition, these three S-HDAg modifications are dispensable for Antigenomic RNA synthesis but are required for genomic RNA synthesis. Furthermore, the three RNA species had different sensitivities to acetylation and deacetylation inhibitors, showing that the metabolic requirements for the synthesis of HDV Antigenomic RNA are different from those for the synthesis of genomic RNA and mRNA. In sum, our data support the hypothesis that the cellular machinery involved in the synthesis of HDV Antigenomic RNA is different from that of genomic RNA synthesis and mRNA transcription, even though the Antigenomic RNA and the mRNA are made from the same RNA template. We propose that acetylation and deacetylation of HDAg may provide a molecular switch for the synthesis of the different HDV RNA species.
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Large Hepatitis Delta Antigen Is Not a Suppressor of Hepatitis Delta Virus RNA Synthesis once RNA Replication Is Established
Journal of virology, 2002Co-Authors: Thomas B. Macnaughton, Michael M.c. LaiAbstract:Moderation of Hepatitis Delta virus (HDV) replication is a likely prerequisite in the establishment of chronic infections and is thought to be mediated by the intracellular accumulation of large Hepatitis Delta Antigen (L-HDAg). The regulatory role of this protein was suggested from several studies showing that cotransfection of plasmid cDNAs expressing both L-HDAg and HDV RNA results in a potent inhibition of HDV RNA replication. However, since this approach differs significantly from natural HDV infections, where HDV RNA replication is initiated from an RNA template, and L-HDAg appears only late in the replication cycle, it remains unclear whether L-HDAg can modulate HDV RNA replication in the natural HDV replication cycle. In this study, we investigated the effect of L-HDAg, produced as a result of the natural HDV RNA editing event, on HDV RNA replication. The results showed that following cDNA-free HDV RNA transfection, a steady-state level of RNA was established at 3 to 4 days posttransfection. The same level of HDV RNA was reached when a mutant HDV genome unable to make L-HDAg was used, suggesting that L-HDAg did not play a role. The rates of HDV RNA synthesis, as measured by metabolic labeling experiments, were identical at 4 and 8 days posttransfection and in the wild type and the L-HDAg-deficient mutant. We further examined the effect of overexpression of L-HDAg at various stages of the HDV replication cycle, showing that HDV RNA synthesis was resistant to L-HDAg when it was overexpressed 3 days after HDV RNA replication had initiated. Finally, we showed that, contrary to conventional thinking, L-HDAg alone, at a certain molar ratio with HDV RNA, can initiate HDV RNA replication. Thus, L-HDAg does not inherently inhibit HDV RNA synthesis. Taken together, these results indicated that L-HDAg affects neither the rate of HDV RNA synthesis nor the final steady-state level of HDV RNA and that L-HDAg is unlikely to act as an inhibitor of HDV RNA replication in the natural HDV replication cycle.
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Recombinant Hepatitis Delta Antigen from E. coli promotes Hepatitis Delta virus RNA replication only from the genomic strand but not the Antigenomic strand.
Virology, 2000Co-Authors: Gwo-tarng Sheu, Michael M.c. LaiAbstract:Hepatitis Delta Antigen (HDAg) of Hepatitis Delta virus (HDV) typically consists of two related protein species. The small HDAg (S-HDAg) is a 24-kDa protein of 195 amino acids and the large HDAg (L-HDAg) is a 27-kDa protein with an additional 19 amino acids at its C-terminus. These two proteins have distinct functions in the HDV life cycle. We have developed conditions for expressing S-HDAg and L-HDAg in E. coli as soluble proteins to facilitate large-scale purification. These proteins were purified to homogeneity and shown to be biologically active. Transfection of the purified recombinant S-HDAg together with HDV genomic RNA resulted in viral RNA replication. Surprisingly, the purified S-HDAg could not initiate replication from the Antigenomic-sense HDV RNA, even though the latter led to RNA replication when transfected with an mRNA encoding the S-HDAg. These results suggest that initiation of HDV RNA synthesis from the Antigenomic RNA may require a form of HDAg that is modified in mammalian cells; in contrast, RNA synthesis from the genomic RNA could be initiated by the recombinant S-HDAg from E. coli. Interestingly, the purified L-HDAg appeared as multiple protein species, including one corresponding to S-HDAg, probably as a result of degradation. The partially proteolyzed L-HDAg also initiated HDV RNA replication under the same conditions. These results add to the mounting evidence that genomic- and Antigenomic-strand HDV RNA syntheses are carried out by different mechanisms.
John L. Casey - One of the best experts on this subject based on the ideXlab platform.
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Hepatitis Delta Antigen Regulates mRNA and Antigenome RNA Levels during Hepatitis Delta Virus Replication.
Journal of virology, 2019Co-Authors: Kaneemozhe Harichandran, Yiran Shen, Susannah Stephenson Tsoris, See-chi Lee, John L. CaseyAbstract:Hepatitis Delta virus (HDV) is a satellite of Hepatitis B virus that increases the severity of acute and chronic liver disease. HDV produces three processed RNAs that accumulate in infected cells: the circular genome; the circular Antigenome, which serves as a replication intermediate; and lesser amounts of the mRNA, which encodes the sole viral protein, Hepatitis Delta Antigen (HDAg). The HDV genome and Antigenome RNAs form ribonucleoprotein complexes with HDAg. Although HDAg is required for HDV replication, it is not known how the relative amounts of HDAg and HDV RNA affect replication, or whether HDAg synthesis is regulated by the virus. Using a novel transfection system in which HDV replication is initiated using in vitro-synthesized circular HDV RNAs, HDV replication was found to depend strongly on the relative amounts of HDV RNA and HDAg. HDV controls these relative amounts via differential effects of HDAg on the production of HDV mRNA and Antigenome RNA, both of which are synthesized from the genome RNA template. mRNA synthesis is favored at low HDAg levels but becomes saturated at high HDAg concentrations. Antigenome RNA accumulation increases linearly with HDAg and dominates at high HDAg levels. These results provide a conceptual model for how HDV Antigenome RNA production and mRNA transcription are controlled from the earliest stage of infection onward and also demonstrate that, in this control, HDV behaves similarly to other negative-strand RNA viruses, even though there is no genetic similarity between them.IMPORTANCE Hepatitis Delta virus (HDV) is a satellite of Hepatitis B virus that increases the severity of liver disease; approximately 15 million people are chronically infected worldwide. There are no licensed therapies available. HDV is not related to any known virus, and few details regarding its replication cycle are known. One key question is whether and how HDV regulates the relative amounts of viral RNA and protein in infected cells. Such regulation might be important because the HDV RNA and protein form complexes that are essential for HDV replication, and the proper stoichiometry of these complexes could be critical for their function. Our results show that the relative amounts of HDV RNA and protein in cells are indeed important for HDV replication and that the virus does control them. These observations indicate that further study of these regulatory mechanisms is required to better understand replication of this serious human pathogen.
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Hepatitis Delta Antigen requires a flexible quasi-double-stranded RNA structure to bind and condense Hepatitis Delta virus RNA in a ribonucleoprotein complex.
Journal of virology, 2014Co-Authors: Brittany L. Griffin, Sergey Chasovskikh, Anatoly Dritschilo, John L. CaseyAbstract:UNLABELLED The circular genome and Antigenome RNAs of Hepatitis Delta virus (HDV) form characteristic unbranched, quasi-double-stranded RNA secondary structures in which short double-stranded helical segments are interspersed with internal loops and bulges. The ribonucleoprotein complexes (RNPs) formed by these RNAs with the virus-encoded protein Hepatitis Delta Antigen (HDAg) perform essential roles in the viral life cycle, including viral replication and virion formation. Little is understood about the formation and structure of these complexes and how they function in these key processes. Here, the specific RNA features required for HDAg binding and the topology of the complexes formed were investigated. Selective 2'OH acylation analyzed by primer extension (SHAPE) applied to free and HDAg-bound HDV RNAs indicated that the characteristic secondary structure of the RNA is preserved when bound to HDAg. Notably, the analysis indicated that predicted unpaired positions in the RNA remained dynamic in the RNP. Analysis of the in vitro binding activity of RNAs in which internal loops and bulges were mutated and of synthetically designed RNAs demonstrated that the distinctive secondary structure, not the primary RNA sequence, is the major determinant of HDAg RNA binding specificity. Atomic force microscopy analysis of RNPs formed in vitro revealed complexes in which the HDV RNA is substantially condensed by bending or wrapping. Our results support a model in which the internal loops and bulges in HDV RNA contribute flexibility to the quasi-double-stranded structure that allows RNA bending and condensing by HDAg. IMPORTANCE RNA-protein complexes (RNPs) formed by the Hepatitis Delta virus RNAs and protein, HDAg, perform critical roles in virus replication. Neither the structures of these RNPs nor the RNA features required to form them have been characterized. HDV RNA is unusual in that it forms an unbranched quasi-double-stranded structure in which short base-paired segments are interspersed with internal loops and bulges. We analyzed the role of the HDV RNA sequence and secondary structure in the formation of a minimal RNP and visualized the structure of this RNP using atomic force microscopy. Our results indicate that HDAg does not recognize the primary sequence of the RNA; rather, the principle contribution of unpaired bases in HDV RNA to HDAg binding is to allow flexibility in the unbranched quasi-double-stranded RNA structure. Visualization of RNPs by atomic force microscopy indicated that the RNA is significantly bent or condensed in the complex.
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Arginine-Rich Motifs Are Not Required for Hepatitis Delta Virus RNA Binding Activity of the Hepatitis Delta Antigen
Journal of virology, 2013Co-Authors: Leighton H. Daigh, Brittany L. Griffin, Ali Soroush, Murad R. Mamedov, John L. CaseyAbstract:Hepatitis Delta virus (HDV) replication and packaging require interactions between the unbranched rodlike structure of HDV RNA and Hepatitis Delta Antigen (HDAg), a basic, disordered, oligomeric protein. The tendency of the protein to bind nonspecifically to nucleic acids has impeded analysis of HDV RNA protein complexes and conclusive determination of the regions of HDAg involved in RNA binding. The most widely cited model suggests that RNA binding involves two proposed arginine-rich motifs (ARMs I and II) in the middle of HDAg. However, other studies have questioned the roles of the ARMs. Here, binding activity was analyzed in vitro using HDAg-160, a C-terminal truncation that binds with high affinity and specificity to HDV RNA segments in vitro. Mutation of the core arginines of ARM I or ARM II in HDAg-160 did not diminish binding to HDV unbranched rodlike RNA. These same mutations did not abolish the ability of full-length HDAg to inhibit HDV RNA editing in cells, an activity that involves RNA binding. Moreover, only the N-terminal region of the protein, which does not contain the ARMs, was cross-linked to a bound HDV RNA segment in vitro. These results indicate that the amino-terminal region of HDAg is in close contact with the RNA and that the proposed ARMs are not required for binding HDV RNA. Binding was not reduced by mutation of additional clusters of basic amino acids. This result is consistent with an RNA-protein complex that is formed via numerous contacts between the RNA and each HDAg monomer.
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Multimerization of Hepatitis Delta Antigen is a critical determinant of RNA binding specificity.
Journal of virology, 2009Co-Authors: Brian C. Lin, Dawn A. Defenbaugh, John L. CaseyAbstract:Hepatitis Delta virus (HDV) RNA forms an unbranched rod structure that is associated with Hepatitis Delta Antigen (HDAg) in cells replicating HDV. Previous in vitro binding experiments using bacterially expressed HDAg showed that the formation of a minimal ribonucleoprotein complex requires an HDV unbranched rod RNA of at least about 300 nucleotides (nt) and suggested that HDAg binds the RNA as a multimer of fixed size. The present study specifically examines the role of HDAg multimerization in the formation of the HDV ribonucleoprotein complex (RNP). Disruption of HDAg multimerization by site-directed mutagenesis was found to profoundly alter the nature of RNP formation. Mutant HDAg proteins defective for multimerization exhibited neither the 300-nt RNA size requirement for binding nor specificity for the unbranched rod structure. The results unambiguously demonstrate that HDAg binds HDV RNA as a multimer and that the HDAg multimer is formed prior to binding the RNA. RNP formation was found to be temperature dependent, which is consistent with conformational changes occurring on binding. Finally, analysis of RNPs constructed with unbranched rod RNAs successively longer than the minimum length indicated that multimeric binding is not limited to the first HDAg bound and that a minimum RNA length of between 604 and 714 nt is required for binding of a second multimer. The results confirm the previous proposal that HDAg binds as a large multimer and demonstrate that the multimer is a critical determinant of the structure of the HDV RNP.
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Hepatitis Delta Antigen Requires a Minimum Length of the Hepatitis Delta Virus Unbranched Rod RNA Structure for Binding
Journal of virology, 2009Co-Authors: Dawn A. Defenbaugh, Matthew Johnson, Renxiang Chen, Ying Yi Zheng, John L. CaseyAbstract:Hepatitis Delta virus (HDV) is a subviral pathogen that increases the severity of liver disease caused by Hepatitis B virus. Both the small circular RNA genome and its complement, the Antigenome, form a characteristic unbranched rod structure in which approximately 70% of the nucleotides are base paired. These RNAs are associated with the sole virally encoded protein, Hepatitis Delta Antigen (HDAg), in infected cells; however, the nature of the ribonucleoprotein complexes (RNPs) is not well understood. Previous analyses of binding in vitro using native, bacterially expressed HDAg have been hampered by a lack of specificity for HDV RNA. Here, we show that removal of the C-terminal 35 amino acids of HDAg yields a native, bacterially expressed protein, HDAg-160, that specifically binds HDV unbranched rod RNA with high affinity. In an electrophoretic mobility shift assay, this protein produced a discrete, micrococcal nuclease-resistant complex with an ∼400-nucleotide (nt) segment of HDV unbranched rod RNA. Binding occurred with several segments of HDV RNA, although with various affinities and efficiencies. Analysis of the effects of deleting segments of the unbranched rod indicated that binding did not require one or two specific binding sites within these RNA segments. Rather, a minimum-length HDV RNA unbranched rod approximately 311 nt was essential for RNP formation. The results are consistent with a model in which HDAg binds HDV unbranched rod RNA as multimers of fixed size rather than as individual subunits.
Soon B. Hwang - One of the best experts on this subject based on the ideXlab platform.
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Hepatitis Delta virus large Antigen sensitizes to TNF-α-induced NF-κB signaling
Molecules and Cells, 2009Co-Authors: Chul-yong Park, Sang Min Kang, Yun-sook Lim, Soon B. HwangAbstract:Hepatitis Delta virus (HDV) infection causes fulminant Hepatitis and liver cirrhosis. To elucidate the molecular mechanism of HDV pathogenesis, we examined the effects of HDV viral proteins, the small Hepatitis Delta Antigen (SHDAg) and the large Hepatitis Delta Antigen (LHDAg), on NF-κB signaling pathway. In this study, we demonstrated that TNF-α-induced NF-κB transcriptional activation was increased by LHDAg but not by SHDAg in both HEK293 and Huh7 cells. Furthermore, LHDAg promoted TRAF2-induced NF-κB activation. Using coimmunoprecipitation assays, we demonstrated that both SHDAg and LHDAg interacted with TRAF2 protein. We showed that isoprenylation of LHDAg was not required for the increase of NF-κB activity. We further showed that only LHDAg but not SHDAg increased the TNF-α-mediated nuclear translocation of p65. This was accomplished by activation of IκBα degradation by LHDAg. Finally, we demonstrated that LHDAg augmented the COX-2 expression level in Huh7 cells. These data suggest that LHDAg modulates NF-κB signaling pathway and may contribute to HDV pathogenesis.
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large Hepatitis Delta Antigen modulates transforming growth factor β signaling cascades implication of Hepatitis Delta virus induced liver fibrosis
Gastroenterology, 2007Co-Authors: Soo-ho Choi, Sook Hyang Jeong, Soon B. HwangAbstract:Background & Aims: Transforming growth factor-β (TGF-β) has been implicated in the pathogenesis of liver disease. TGF-β is involved in liver regeneration and in the fibrotic and cirrhotic transformation with Hepatitis viral infection. Hepatitis Delta virus (HDV) infection causes fulminant Hepatitis and liver cirrhosis. To elucidate the molecular mechanism of HDV pathogenesis, we examined the effects of HDV-encoded–only protein, the small Hepatitis Delta Antigen (SHDAg), and the large Hepatitis Delta Antigen (LHDAg), on TGF-β– and c-Jun–induced signaling cascades. Methods: The effects of either SHDAg or LHDAg on TGF-β– and c-Jun–induced signaling cascades in Huh7 and Cos7 cells were investigated by luciferase reporter gene assay, immunoprecipitation assay, electrophoretic mobility shift assay, Western blot analysis, and confocal microscopy analysis. Results: The LHDAg, but not the SHDAg, potentiated TGF-β– and c-Jun–induced signal activation, and the isoprenylation of LHDAg played a major role in signaling cascades. LHDAg synergistically activated Hepatitis B virus X protein–mediated TGF-β and AP-1 signaling cascades. In addition, LHDAg enhanced the protein expression level of TGF-β–induced plasminogen activator inhibitor-1. Conclusions: LHDAg may induce liver fibrosis through the regulation of TGF-β–induced signal transductions. This regulation of TGF-β–mediated signaling is accomplished by the isoprenylation of LHDAg, which is a novel mechanism involved in HDV pathogenesis.
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Large Hepatitis Delta Antigen Modulates Transforming Growth Factor-β Signaling Cascades: Implication of Hepatitis Delta Virus–Induced Liver Fibrosis
Gastroenterology, 2006Co-Authors: Soo-ho Choi, Sook Hyang Jeong, Soon B. HwangAbstract:Background & Aims: Transforming growth factor-β (TGF-β) has been implicated in the pathogenesis of liver disease. TGF-β is involved in liver regeneration and in the fibrotic and cirrhotic transformation with Hepatitis viral infection. Hepatitis Delta virus (HDV) infection causes fulminant Hepatitis and liver cirrhosis. To elucidate the molecular mechanism of HDV pathogenesis, we examined the effects of HDV-encoded–only protein, the small Hepatitis Delta Antigen (SHDAg), and the large Hepatitis Delta Antigen (LHDAg), on TGF-β– and c-Jun–induced signaling cascades. Methods: The effects of either SHDAg or LHDAg on TGF-β– and c-Jun–induced signaling cascades in Huh7 and Cos7 cells were investigated by luciferase reporter gene assay, immunoprecipitation assay, electrophoretic mobility shift assay, Western blot analysis, and confocal microscopy analysis. Results: The LHDAg, but not the SHDAg, potentiated TGF-β– and c-Jun–induced signal activation, and the isoprenylation of LHDAg played a major role in signaling cascades. LHDAg synergistically activated Hepatitis B virus X protein–mediated TGF-β and AP-1 signaling cascades. In addition, LHDAg enhanced the protein expression level of TGF-β–induced plasminogen activator inhibitor-1. Conclusions: LHDAg may induce liver fibrosis through the regulation of TGF-β–induced signal transductions. This regulation of TGF-β–mediated signaling is accomplished by the isoprenylation of LHDAg, which is a novel mechanism involved in HDV pathogenesis.
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Large Hepatitis Delta Antigen is phosphorylated at multiple sites and phosphorylation is associated with protein conformational change.
Intervirology, 2002Co-Authors: Soo-ho Choi, Kyu-jin Park, Soon B. HwangAbstract:Hepatitis Delta Antigen (HDAg) consists of two species, small HDAg (SHDAg) and large HDAg (LHDAg), which are identical in sequence with the exception that the large form contains an additional 19 amin
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Cell cycle arrest mediated by Hepatitis Delta Antigen
FEBS letters, 1999Co-Authors: Soon B. Hwang, Kyu-jin ParkAbstract:Hepatitis Delta Antigen (HDAg) is the only viral-encoded protein of the Hepatitis Delta virus (HDV). This protein has been extensively characterized with respect to its biochemical and functional properties. However, the molecular mechanism responsible for persistent HDV infection is not yet clear. Previously, we reported that overexpression of HDAg protects insect cells from baculovirus-induced cytolysis [Hwang, S.B. Park, K.-J. and Kim, Y.S. (1998) Biochem. Biophys. Res. Commun. 244, 652–658]. Here we report that HDAg mediates cell cycle arrest when overexpressed in recombinant baculovirus-infected insect cells. Flow cytometry analysis has shown that HDAg expression in Spodoptera frugiperda cells causes an accumulation of substantial amounts of polyploid DNA in the absence of cell division. This phenomenon may be partly responsible for the persistent infection of chronic HDV patients.
Jya-wei Cheng - One of the best experts on this subject based on the ideXlab platform.
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Solution structure of an N-capping peptide from the N-terminal leucine-repeat region of Hepatitis Delta Antigen.
Archives of biochemistry and biophysics, 2000Co-Authors: Yuan-chao Lou, Ming-tao Pai, I-jin Lin, Jya-wei ChengAbstract:Abstract Hepatitis Delta virus (HDV) is a satellite virus of the Hepatitis B virus (HBV) which provides the surface Antigen for the viral coat. The RNA genome of HDV encodes two proteins, the small Delta Antigen and the large δ Antigen, which differ only with the latter having an additional 19 amino acids at the C-terminus. Previously, we have shown that dAg 24–50 , a synthetic peptide corresponding to residues 24–50 of the N-terminal leucine-repeat region of Hepatitis Delta Antigen, binds to the viral RNA and forms an α-helical conformation in TFE-containing solution. However, it exhibited low α-helicity (less than 5%) in the absence of TFE. In order to obtain biologically active Delta Antigen peptides with higher structural stability in solution, an N-capping 21-residue polypeptide corresponding to residues 24–38 of Hepatitis Delta Antigen (dAg Cap24–38am ) was synthesized and, surprisingly, its solution structure was found to be a stable α-helix (64%) by circular dichroism and 1 H NMR techniques. Moreover, the structure of the capping box shows the characteristic L-shaped bend perpendicular to the helix axis. This structural knowledge provides a molecular basis for understanding the role of the N-terminal leucine-repeat region of Hepatitis Delta Antigen and has a significant potential for the development of diagnostic and therapeutic methods for HDV.
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Solution structure and RNA-binding activity of the N-terminal leucine-repeat region of Hepatitis Delta Antigen.
Proteins, 1999Co-Authors: I-jin Lin, Ming-tao Pai, Yuan-chao Lou, Jya-wei ChengAbstract:Hepatitis Delta virus (HDV) is a satellite virus of the Hepatitis B virus (HBV) which provides the surface Antigen for the viral coat. The RNA genome of HDV encodes two proteins: the small Delta Antigen and the large Delta Antigen. The two proteins resemble each other except for the presence of an additional 19 amino acids at the C terminus of the latter species. We have found that the N-terminal leucine-repeat region of Hepatitis Delta Antigen (HDAg) binds to the autolytic domain of HDV genomic RNA and attenuates its autolytic activity. A 27-residue polypeptide corresponding to residues 24–50 of HDAg, designated dAg24–50, was synthesized, and its solution structure was found to be an α-helix by circular dichroism and 1H-nuclear magnetic resonance (NMR) techniques. Binding affinity of dAg24–50 with HDV genomic RNA was found to increase with its α-helical content, and it was further confirmed by modifying its N- and C-terminal groups. Furthermore, the absence of RNA binding activity in the mutant peptides, dAgM24–50am and dAgMAc24–50am, in which Lys38, Lys39, and Lys40 were changed to Glu, indicates a possible involvement of these residues in their binding activity. Structural knowledge of the N-terminal leucine-repeat region of HDAg thus provides a molecular basis for the understanding of its role in the interaction with RNA. Proteins 1999;37:121–129. © 1999 Wiley-Liss, Inc.
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Local helix content and RNA-binding activity of the N-terminal leucine-repeat region of Hepatitis Delta Antigen.
Journal of biomolecular NMR, 1998Co-Authors: Jya-wei Cheng, I-jin Lin, Yuan-chou Lou, Ming-tao PaiAbstract:Hepatitis Delta virus (HDV) is a satellite virus of the Hepatitis B virus (HBV) which provides the surface Antigen for the viral coat. Our results show that the N-terminal leucine-repeat region of Hepatitis Delta Antigen (HDAg), encompassing residues 24–50, binds to the autolytic domain of HDV genomic RNA and attenuates its autolytic activity. The solution conformation of a synthetic peptide corresponding to residues 24–50 of HDAg as determined by two-dimensional 1H NMR and circular dichroism techniques is found to be an α-helix. The local helix content of this peptide was analyzed by NOEs and coupling constants. Mutagenesis studies indicate that Lys38, Lys39, and Lys40 within this α-helical peptide may be directly involved in RNA binding. A structural knowledge of the N-terminal leucine-repeat region of HDAg thus provides a molecular basis for understanding its role in the interaction with RNA.
Ming-tao Pai - One of the best experts on this subject based on the ideXlab platform.
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Solution structure of an N-capping peptide from the N-terminal leucine-repeat region of Hepatitis Delta Antigen.
Archives of biochemistry and biophysics, 2000Co-Authors: Yuan-chao Lou, Ming-tao Pai, I-jin Lin, Jya-wei ChengAbstract:Abstract Hepatitis Delta virus (HDV) is a satellite virus of the Hepatitis B virus (HBV) which provides the surface Antigen for the viral coat. The RNA genome of HDV encodes two proteins, the small Delta Antigen and the large δ Antigen, which differ only with the latter having an additional 19 amino acids at the C-terminus. Previously, we have shown that dAg 24–50 , a synthetic peptide corresponding to residues 24–50 of the N-terminal leucine-repeat region of Hepatitis Delta Antigen, binds to the viral RNA and forms an α-helical conformation in TFE-containing solution. However, it exhibited low α-helicity (less than 5%) in the absence of TFE. In order to obtain biologically active Delta Antigen peptides with higher structural stability in solution, an N-capping 21-residue polypeptide corresponding to residues 24–38 of Hepatitis Delta Antigen (dAg Cap24–38am ) was synthesized and, surprisingly, its solution structure was found to be a stable α-helix (64%) by circular dichroism and 1 H NMR techniques. Moreover, the structure of the capping box shows the characteristic L-shaped bend perpendicular to the helix axis. This structural knowledge provides a molecular basis for understanding the role of the N-terminal leucine-repeat region of Hepatitis Delta Antigen and has a significant potential for the development of diagnostic and therapeutic methods for HDV.
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Solution structure and RNA-binding activity of the N-terminal leucine-repeat region of Hepatitis Delta Antigen.
Proteins, 1999Co-Authors: I-jin Lin, Ming-tao Pai, Yuan-chao Lou, Jya-wei ChengAbstract:Hepatitis Delta virus (HDV) is a satellite virus of the Hepatitis B virus (HBV) which provides the surface Antigen for the viral coat. The RNA genome of HDV encodes two proteins: the small Delta Antigen and the large Delta Antigen. The two proteins resemble each other except for the presence of an additional 19 amino acids at the C terminus of the latter species. We have found that the N-terminal leucine-repeat region of Hepatitis Delta Antigen (HDAg) binds to the autolytic domain of HDV genomic RNA and attenuates its autolytic activity. A 27-residue polypeptide corresponding to residues 24–50 of HDAg, designated dAg24–50, was synthesized, and its solution structure was found to be an α-helix by circular dichroism and 1H-nuclear magnetic resonance (NMR) techniques. Binding affinity of dAg24–50 with HDV genomic RNA was found to increase with its α-helical content, and it was further confirmed by modifying its N- and C-terminal groups. Furthermore, the absence of RNA binding activity in the mutant peptides, dAgM24–50am and dAgMAc24–50am, in which Lys38, Lys39, and Lys40 were changed to Glu, indicates a possible involvement of these residues in their binding activity. Structural knowledge of the N-terminal leucine-repeat region of HDAg thus provides a molecular basis for the understanding of its role in the interaction with RNA. Proteins 1999;37:121–129. © 1999 Wiley-Liss, Inc.
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Local helix content and RNA-binding activity of the N-terminal leucine-repeat region of Hepatitis Delta Antigen.
Journal of biomolecular NMR, 1998Co-Authors: Jya-wei Cheng, I-jin Lin, Yuan-chou Lou, Ming-tao PaiAbstract:Hepatitis Delta virus (HDV) is a satellite virus of the Hepatitis B virus (HBV) which provides the surface Antigen for the viral coat. Our results show that the N-terminal leucine-repeat region of Hepatitis Delta Antigen (HDAg), encompassing residues 24–50, binds to the autolytic domain of HDV genomic RNA and attenuates its autolytic activity. The solution conformation of a synthetic peptide corresponding to residues 24–50 of HDAg as determined by two-dimensional 1H NMR and circular dichroism techniques is found to be an α-helix. The local helix content of this peptide was analyzed by NOEs and coupling constants. Mutagenesis studies indicate that Lys38, Lys39, and Lys40 within this α-helical peptide may be directly involved in RNA binding. A structural knowledge of the N-terminal leucine-repeat region of HDAg thus provides a molecular basis for understanding its role in the interaction with RNA.