• BMB Reports
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• 제33권2호
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• pp.126-132
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• 2000

The hepadnaviruses replicate their nucleic acid through a reverse transcription step. The MBP-fused HBV polymerase was expressed in E. coli and purified by using amylase affinity column chromatography. The purified protein represented DNA-dependent DNA polymerase activity. In this report, the MBP-HBV polymerase was shown to lack 3'$\rightarrow$5' exonuclease activity, like other retroviral RTs. The ratio of the insertion efficiency for the wrong versus right vase pairs indicates the misinsertion frequency (f). The nucleotide insertion fidelity (1/f), observed with the MBP-HBV polymerase and HIV-1 RT, was between 60 and 54,000, and between 50 and 73,000, respectively, showing that they are in close range. A relatively efficient nucleotide incorporation by the MBP-HBV polymerase was observed with a specificity of three groups: (1) A : T, T : A>C : G, G : C (matched pairs), (2) A : C, C : A>G: T, T : G (purine-pyrimidine and pyrimidine-purine mispairs), and (3) C : C, A : A, G : G, T : T>T : C, C : T>A : G, G : A (purine-purine or pyrimidine-pyrimidine mispairs), and their order is (1)>(2)>(3). The data from the nucleotide insertion fidelity by the MBP-HBV polymerase suggest that the HBV polymerase may be as error-prone as HIV-1 RT.

• Animal cells and systems
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• 제5권3호
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• pp.195-198
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• 2001

Hepatitis B virus (HBV) polymerase, which possesses the activities of terminal binding, DNA polymerase, reverse transcriptase and RNaseH, has been shown to accomplish viral DNA replication through a pregenomic intermediate. Because the HBV polymerase has not been purified, the expression of HBV polymerase was examined in an E. coli expression system that is under the regulation of arabinose operon. The expressed individual domain containing terminal binding protein, polymerase, or RNaseH turned out to be insoluble. The activities of those domains were not able to be recovered by denaturation and renaturation using urea or guanidine-HCI. The expressed reverse transcriptase containing the polymerase and RNaseH domains became extensively degraded, whereas the proteolysis was reduced in a Ion- mutant. These results indicate that Lon protease proteolyzes the HBV reverse transcriptase expressed in E. coli.

• BMB Reports
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• 제31권5호
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• pp.498-502
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• 1998

HBV polymerase shares several regions of amino acid homology with other DNA-directed and RNA-directed polymerases. The amino acid residues $Asp^{429}$, $Gly^{518}$, $Asp^{551}$, $Lys^{585}$, and $Gly^{641}$ in the conserved motifs A, B', C, D, and E in the polymerase domain of HBV polymerase were mutated to alanine or histidine by in vitro site-directed mutagenesis. Those mutants were overexpressed, purified, and analyzed against DNA-dependent DNA polymerase activity and affinity for DNA binding. All those mutants did not show DNA-dependent DNA polymerase activities indicating that those five amino acid residues are all critical in DNA polymerase activity. South-Western analysis shows that amino acid residues $ASp^{429}$ and $ASp^{551}$ are essential to DNA binding, and $Gly^{318}$ and $Gly^{585}$ also affect DNA binding to a certain extent.

• Asian Pacific Journal of Cancer Prevention
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• 제14권9호
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• pp.5489-5494
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• 2013

In the current study we aimed to show the common YMDD motif mutations in viral polymerase gene in chronic hepatitis B patients during lamivudine and adefovir therapy. Forty-one serum samples obtained from chronic hepatitis B patients (24 male, 17 female; age range: 34-68 years) were included in the study. HBV-DNA was extracted from the peripheral blood of the patients using an extraction kit (Invisorb, Instant Spin DNA/RNA Virus Mini Kit, Germany). A line probe assay and direct sequencing analyses (INNO-LIPA HBV DR v2; INNOGENETICS N.V, Ghent, Belgium) were applied to determine target mutations of the viral polymerase gene in positive HBV-DNA samples. A total of 41 mutations located in 21 different codons were detected in the current results. In 17 (41.5%) patients various point mutations were detected leading to lamivudin, adefovir and/or combined drug resistance. Wild polymerase gene profiles were detected in 24 (58.5%) HBV positive patients of the current cohort. Eight of the 17 samples (19.5%) having rtM204V/I/A missense transition and/or transversion point mutations and resistance to lamivudin. Six of the the mutated samples (14.6%) having rtL180M missense transversion mutation and resistance to combined adefovir and lamivudin. Three of the mutated samples (7.5%) having rtG215H by the double base substituation and resistance to adefovir. Three of the mutated samples (7.5%) having codon rtL181W due to the missense transversion point mutations and showed resistance to combined adefovir and lamivudin. Unreported novel point mutations were detected in the different codons of polymerase gene region in the current HBV positive cohort fromTurkish population. The current results provide evidence that rtL180M and rtM204V/I/A mutations of HBV-DNA may be associated with a poor antiviral response and HBV chronicity during conventional therapy in Turkish patients.

• BMB Reports
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• 제37권2호
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• pp.167-176
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• 2004

Although efficient antiviral lamivudine is used for HBV-infected patients, a prolonged treatment with nucleoside analogs often results in lamivudine-resistant variants. In this study, we evaluated the fidelity of the lamivudine-resistant variants. The FLAG-tagged wild-type (FPolE) and Met550 variants (FPolE/M550A, M550V, and M550I) of HBV DNA polymerases were expressed in insect cells then purified. Like many other reverse transcriptases, no $3'{\rightarrow}5'$ exonuclease activity was detected in the HBV DNA polymerase. Since there is no proofreading activity, then the use of the site-specific nucleotide misincorporation method is beneficial. From the $f_{ins}$ value analysis, it is evident that M550I and M550V exhibit higher fidelity values than the wild-type HBV DNA polymerase, while M550A exhibits similar fidelity values. It is therefore suggested that lamivudine resistance comes from the stringency to dNTP binding and the discrimination of dCTP and lamivudine in M550V and M550I.

• Journal of Microbiology and Biotechnology
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• 제31권1호
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• pp.16-24
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• 2021

Hepatitis B virus (HBV) genome P-encoded protein HBV DNA polymerase (Pol) has long been known as a reverse transcriptase during HBV replication. In this study, we investigated the impact of HBV Pol on host cellular processes, mainly apoptosis, and the underlying mechanisms. We showed a marked reduction in apoptotic rates in the HBV Pol-expressed HepG2 cells compared to controls. Moreover, a series of assays, i.e., yeast two-hybrid, GST pull-down, co-immunoprecipitation, and confocal laser scanning microscopy, identified the host factor eEF1A2 to be associated with HBV Pol. Furthermore, knockdown of eEF1A2 gene by siRNA abrogated the HBV Pol-mediated anti-apoptotic effect with apoptosis induced by endoplasmatic reticulum (ER) stress-inducer thapsigargin (TG), thus suggesting that the host factor eEF1A2 is essential for HBV Pol's anti-apoptosis properties. Our findings have revealed a novel role for HBV Pol in its modulation of apoptosis through integrating with eEF1A2.

• BMB Reports
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• 제33권6호
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• pp.440-447
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• 2000

In this study HepG2 cells were used to express and purify HBV pol proteins. In order to facilitate purification of HBV pol proteins, HBV pol and its deletion mutants were fused to MBP (Maltose Binding Protein). As a result we successfully expressed and partially purified both wild type and mutant recombinant HBV pol proteins by using an amylose resin and anti-MBP antibody. In the case of wild type, the anti-MBP antibody detected three bands. One was full-length and the others were generated by proteolysis of the terminal domain region. The expressed MBP/POL proteins were localized both in the cytoplasm and in the perinuclear region. The purified proteins had polymerase activity toward an exogenous homo-polymer template. The MBP/POL protein also had DNA synthesis activity in vivo, since the MBP/POL expression construct was able to complement a HBV polymerase mutant in trans.

• IMMUNE NETWORK
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• 제3권2호
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• pp.126-135
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• 2003

Background: One of the important factors in the prognosis of chronic hepatitis B patient is the degree of replication of hepatitis B virus (HBV). It has been known that HBV DNA polymerase plays the essential role in the replication of HBV. HBV DNA polymerase is composed of four domains, TP (Terminal protein), spacer, RT (Reverse transcriptase) and RNaseH. Among these domains, tyrosine, the $65^{th}$ residue of TP is an important residue in protein-priming reaction that initiates reverse transcription. If monoclonal antibody that recognizes around tyrosine residue were selected, it could be applied to further study of HBV replication. Methods: To produce TP-specific scFv (single-chain Fv) by phage display, mice were immunized using synthetic TP-peptide contains $57{\sim}80^{th}$ amino acid residues of TP domain. After isolation of mRNA of heavy-variable region ($V_H$) and light-chain variable region ($V_L$) from the spleen of the immunized mouse, DNA of $V_H$ and $V_L$ were obtained by RT-PCR and joined by a DNA linker encoding peptide (Gly4Ser)3 as a scFv DNA fragments. ScFv DNA fragments were cloned into a phagemid vector. scFv was expressed in E.coli TG1 as a fusion protein with E tag and phage gIII. To select the scFv that has specific affinity to TP-peptide from the phage-antibody library, we used two cycles of panning and colony lift assay. Results: The TP-peptide-specific scFv was isolated by selection process using TP-peptide as an antigen. Selected scFv had 30 kDa of protein size and its nucleotide sequences were analyzed. Indirect- and competitive-ELISA revealed that the selected scFv specifically recognized both TP-peptide and the HBV DNA polymerase. Conclusion: The scFv that recognizes the TP domain of the HBV DNA polymerase was isolated by phage display.

• Archives of Pharmacal Research
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• 제19권6호
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• pp.469-474
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• 1996

A rapid and sensitive method has been developed to detect hepatitis B virus DNA (HBV) by nested polymerase chain reaction (PCR) technique with primers specific for the surface and core regions in capillary thermal cycler within 80 min. The lower limit for detection by present PCR method is $10^{-5}$ pg of recombinant HBV DNA which is equivalent to that determined by one round of PCR amplification and Southern blot hybridization analysis. When boiled HBV positive serum was serially diluted 10-fold, HBV DNA was successfully determined in $1{\mu}l-10^{-3}$ of serum. HBV DNA was detected by present method in 69 clinical samples including HBsAg positives and negatives by enzyme-linked immunosorbent assay (ELISA). When serum samples were amplified by nested PCR using surface and core region primers, HBV DNAs were detected in 37 of 69 samples (53.6%) and 18 of 69 samples (26.1%), respectively. These results can inform the infectious state of HBsAg positive pateints. A simple and rapid nested PCR protocol by using boiled serum as DNA template has been described for the clinical utility to determine HBV DNA in human serum.

• 핵의학기술
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• 제23권1호
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• pp.35-39
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• 2019

[목적] B형 간염바이러스(hepatitis B virus, HBV)감염은 전세계적으로 중요한 공중 보건 문제이며 만성간염, 간 경변, 간암의 주요 원인으로 알려져 있으며, 이러한 질환의 진단 및 치료에 B형 간염바이러스의 혈청학적 검사는 필수적이다. 항 바이러스 치료중인 B형 간염 환자를 대상으로 면역방사계수 측정법(IRMA; Immunoradiometric assay)과 화학발광 미세입자 면역분석법(CMIA; Chemiluminescent Micropartical Immunoassay)을 이용하여 HBe-Ag 검사를 시행하였고, 실시간 중합효소 연쇄반응(RT-PCR; Realtime-Polymerase Chain Reaction)법을 이용하여 혈청 내 HBV DNA 검출율 을 비교 분석 하였다. [대상 및 방법] 항 바이러스 치료가 시행중인 B형 간염 환자 270명을 대상으로 HBeAg 혈청 검사와 HBV DNA 정량 검사를 실시하였다. HBeAg 혈청 검사는 검출 원리가 다른 두 가지 혈청학적 검사법(IRMA, CMIA)을 적용 하였고, 혈청 내 HBV DNA는 Abbott m2000 System을 사용하여 실시간 중합효소 연쇄반응(RT-PCR; Realtime-Polymerase Chain Reaction)법으로 정량 측정 하였다. [결과] HBeAg 검출율은 면역방사계수법(IRMA)의 경우 24.1% (65/205), 화학발광 미세입자 면역 분석법(CMIA)에서는 82.2% (222/48)의 결과를 보였다. 혈청학적 검사방법(IRMA, CMIA)에 따른 HBeAg 검사결과의 일치율은 33% (89/270)이다. 실시간 중합효소 연쇄반응(RT-PCR)을 이용한 혈청 내 HBV DNA의 검출율은 29.3% (79/191)를 보였고, 혈청 내 HBV-DNA 농도는 $16IU/mL{\times}1.0{\times}10^9IU/mL$ 이며 검출한계는 <15IU/mL 이다. 면역방사계수법(IRMA)으로 HBeAg 검출결과가 양성일때 55.4%, 그리고 음성일때 20.9%의 HBV DNA 검출율과 $1.1{\times}10^8IU/mL$, $5.7{\times}10^5IU/mL$의 혈청내 HBV DNA농도를 나타냈다. 이에 반해 화학발광 미세입자 면역 분석법(CMIA)의 경우 HBeAg 검출결과가 양성일때 HBV DNA 검출율은 28.4%, 음성일때 33.3%의 결과를 나타냈으며 혈청 내 HBV DNA농도는 $6.0{\times}10^7IU/mL$, $2.4{\times}10^5IU/mL$ 이었다. 면역방사계수법과 화학발광 미세입자 면역 분석법에서 동일하게 HBeAg 검출 결과가 양성인 경우 HBV DNA 검출율은 62.3%의 결과를 보였으며, 혈청 내 HBV DNA 농도는 $1.1{\times}10^8IU/mL$ 이다. [결론] 혈청학적 검사법에 따른 HeAg 검출율은 많은 차이를 보였다. 이러한 차이는 검사kit에 사용된 Ab의 특성과 epitope, HBV의 genotype등 여러 가지 원인으로 생각된다. 혈청학적 검사 결과로 분류 된 그룹별 HBV DNA의 검출율과 농도를 비교한 결과, Group II(IRMA 양성, CMIA 양성, N=53)에서 높은 검출율과 농도를 확인할 수 있었다.