Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.7 (DNA polymerase)
17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hepatitis B virus-like particles (including DANE particles) with DNA polymerase activity but negative for HBs Ag have been identified in NON-A, NON-B hepatitis sera positive for HC Ag. Although specifically associated with the particles, HC Ag is not a surface antigen of the hepatitis C virus identified here for the first time. The relationship of this agent with HBV seems obvious, and deserves further study.
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PMID:[Identification of a virus similar to hepatitis B virus in non-A non-B hepatitis]. 12 Jul 82

We assessed the prevalence and clinical significance of antibodies to hepatitis C virus among a cohort of 148 patients with chronic hepatitis B virus infection. Sixteen patients (11%) had anti-hepatitis C virus detectable by enzyme-linked immunoassay. The results from eight of these patients were positive by recombinant immunoblot assay. The results of recombinant immunoblot assay testing were not consistent; therefore the analysis of the patients' data was based on anti-hepatitis C virus enzyme-linked immunoassay results. Patients with chronic hepatitis B with anti-hepatitis C virus were more likely to be cirrhotic (44% vs. 21%) and to have decompensated liver disease (24% vs. 6%). Hepatitis B virus replication appeared to be suppressed in patients with both infections as measured by hepatitis B virus-associated DNA polymerase activity (mean = 2,055 vs. 2,555 cpm). Human immunodeficiency virus infection was more common in the anti-hepatitis C virus positive group (36% vs. 11%). Thus hepatitis C virus appears to suppress hepatitis B virus replication and to cause more severe liver disease in patients with chronic hepatitis B infection.
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PMID:The significance of antibody to hepatitis C virus in patients with chronic hepatitis B. 164 40

Sequence-Independent, Single-Primer Amplification (SISPA) is a primer initiated technique that requires target sequence modification to achieve the non-selective logarithmic amplification of heterogeneous DNA populations. The method contrasts with the polymerase chain reaction (PCR), and its modified approaches, that have as their objective the amplification of unique or homologous sequences. SISPA requires the directional ligation of an asymmetric linker/primer oligonucleotide onto the target population of blunt ended DNA molecules. The common end sequence allows one strand of the double-stranded linker/primer to be used in repeated rounds of annealing, extension and denaturation in the presence of thermostable Taq DNA polymerase. The linker/primers contain restriction endonuclease sites to facilitate the molecular cloning of as little as 1 pg of starting material after amplification. SISPA is especially useful when the nucleotide sequence of the desired molecule is both unknown and present in limited amounts making its recovery by standard cloning procedures technically difficult. These conditions are present in the initial isolation and cloning of previously uncharacterized viral genomes. The application and quantitation of SISPA is described, together with its utility in the cloning and recovery of low abundance genetic sequences, as illustrated here with the hepatitis C virus.
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PMID:Sequence-independent, single-primer amplification (SISPA) of complex DNA populations. 166 49

Enzyme-linked immunosorbent assays for detecting antibodies against hepatitis C virus and the polymerase chain reaction were tested in 82 chronic hepatitis B surface antigen carriers for their accuracy in diagnosing patients coinfected with hepatitis B and C viruses. To clarify the role of each virus in chronic hepatitis, serologic assays against hepatitis B virus were also tested. Thirteen (14.9%), 14 (17.1%) and 15 (18.3%) patients were anti-HCV positive using C100 (HCV1), JCC, and a second generation test (HCV2), respectively. HCV RNA was detected by polymerase chain reaction in 9 of 18 anti-HCV-positive cases. Although HCV1 assays were not sufficient, either the JCC or HCV2 assay detected all polymerase chain reaction-positive cases. Fifteen of 18 specimens that were positive in at least one of the three ELISA were seronegative for the hepatitis B e antigen. As judged by HBV DNA polymerase activity, titers of hepatitis B surface antigen and immunoglobulin A antibody against hepatitis B core antigen (IgA anti-HBc), activity of hepatitis B virus replication and immune response against hepatitis B virus in patients with coinfection was decreased to the level of hepatitis B virus asymptomatic carriers. These results show that hepatitis C virus appears to be the primary cause of active hepatitis in most patients with hepatitis B and hepatitis C virus coinfection.
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PMID:Coinfection of hepatitis C virus in patients with chronic hepatitis B infection. 752 35

A synthetic gene encoding the hepatitis C virus (HCV) nucleocapsid protein was constructed and expressed in E. coli. To synthesize this gene, we developed a new method that results in the enzymatic synthesis of long polydeoxyribonucleotides from oligodeoxyribonucleotides. The method, designated as the 'Exchangeable Template Reaction' (ETR), uses oligonucleotides as templates for DNA polymerase. A special mechanism was designed to exchange the templates during the polymerase reaction. The mechanism relies on the formation of a single-stranded 3'-protrusion at the 'growing point' of the elongating DNA such that it can be subsequently annealed, in a sequence-specific manner, with the next synthetic oligonucleotide. When annealed to the 3'-protrusion, the added oligonucleotide becomes a template for DNA polymerase, and the protruding 3'-end of the double-stranded DNA is used as the primer. The HCV nucleocapsid gene was assembled with DNA ligase from three fragments synthesized by ETR. The data verify that this method is efficient. The main advantage of ETR is the ability to combine more than two oligonucleotides in one tube together with polymerase and an enzymatic activity that produces a 3'-protrusion (e.g., BstXI) rather than the sequential addition of each component. The data demonstrate that as many as five oligonucleotides can be used simultaneously, resulting in a synthesized DNA fragment of designed sequence. The synthetic gene expressed in E. coli produced a 27 kDa protein that specifically interacted with antibodies from sera obtained from HCV-infected individuals.
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PMID:Synthetic gene for the hepatitis C virus nucleocapsid protein. 768 45

Amplification of RNA by the polymerase chain reaction (PCR) is normally a two-step process requiring separate enzymes and buffer conditions. We describe a combined reverse transcription-PCR (RT-PCR) assay for hepatitis C virus (HCV) RNA amplification in which a single enzyme and buffer condition are used. In this assay, both the RT and PCR steps are carried out with the thermoactive DNA polymerase of Thermus thermophilus. A transcription vector containing HCV sequences has also been constructed to generate quantifiable HCV RNA templates that can be used to optimize reaction conditions and to assess the efficiency of amplification. Amplification from < or = 100 copies of RNA was detected reproducibly by gel electrophoresis. The assay sensitivity was increased to 10 RNA copies by hybridization to a probe. The patterns of viremia in three individuals infected with HCV were examined by amplification of HCV RNA from plasma samples collected serially over a period of 1 year. These results were correlated with the times of seroconversion and the onset of rise in levels of alanine aminotransferase in serum. In all three subjects, HCV RNA was detected prior to seroconversion and the initial rise in levels of alanine aminotransferase in serum. Upon seroconversion, HCV RNA fell to a level below the detection limit of the assay. This pattern of transient viremia appears to be characteristic of acute, resolving HCV infections. The combined RT-PCR assay is a sensitive method which circumvents the problems associated with PCR amplification of RNA. Using this assay, we demonstrated that three donors infected by the same index case all have similar patterns of viremia.
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PMID:Detection of hepatitis C virus RNA by a combined reverse transcription-polymerase chain reaction assay. 838 51

The aim of this study was to compare the sensitivity and specificity of conventional procedures (in-house one-stage polymerase chain reaction (PCR) and in-house nested PCR) and of new technologies (rTth DNA polymerase (Amplicor), branched-DNA, NASBA (nucleic acid amplification system)) for the qualitative detection of hepatitis C virus (HCV) RNA in serum of HCV-infected individuals. Serum samples from 37 anti-HCV-positive individuals (15 with a normal alanine aminotransferase (ALT) level, 22 with an elevated ALT level) and 10 anti-HCV-negative individuals as negative controls were studied. A second panel, including 9 diluted serum samples (from 1/10 to 1/100,000) was constituted to establish the differences of sensitivity of the 5 procedures with small quantities of HCV RNA in the serum. The anti-HCV-positive individuals with elevated ALT gave positive results with all 5 procedures. In patients with a normal ALT level, the assays with the highest sensitivity were Amplicor, NASBA and nested RT-PCR, followed by one-stage RT-PCR, then branched-DNA. One false-positive result was observed with Amplicor, and two with in-house nested PCR. On diluted samples, Amplicor, NASBA and nested PCR appeared more sensitive than one-stage PCR and branched-DNA. It is concluded that new procedures have satisfactory sensitivity and specificity and could advantageously replace the conventional PCR procedures for the routine qualitative detection of serum HCV RNA.
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PMID:Comparative study of conventional and novel strategies for the detection of hepatitis C virus RNA in serum: amplicor, branched-DNA, NASBA and in-house PCR. 853 May 67

Among the six species of hepatitis viruses, HBV (hepatitis B virus) and HCV (hepatitis C virus) can induce persistent infection. HBV and HCV are transmitted parenterally, of which maternal transmission and transfusion-associated infection is a major route respectively. We opened the special clinic for carriers detected through blood donation, and followed them at regular intervals for their health care. The prevalence rate of HBV carriers decreased from 3.0% to 1.2% in these 10 years, and that of HCV decreased from 0.9 to 0.4% in these 4 years. Prevalence rate of HBV peaks at 50s and that of HCV peaks at 60s. Due to nearly complete screening of donated blood, post-transfusion hepatitis almost disappeared. HBV vaccine for neonates born from infected mothers reduced the new incidence of HBV carriers. In HBV carriers seroconversion of HBeAg to HBeAb occurs at teens with transient hepatitis and appearance of mutant virus. Ninety percent of the carriers remains healthy for the lifetime but some of them aggravate into chronic hepatitis leading to HCC (hepatocellular carcinoma). In HCV acute infection at adult age succeeds to chronic infection and eventually to liver cirrhosis with sporadic appearance of HCC. On the other hand, less than 50% of HCV carriers seem to be asymptomatic and do not lead to grave disease. In HBV carriers tendency to reject the virus occurs and eventually HBV is cleared in some percentage of the population. In contrast HCV does not tend to be cleared. HBsAb is a defensive antibody. In contrast HCVAb is not a defensive antibody but an infective antibody like HBcAb. DNA polymerase is a good marker of disease state in HBV, and HCV RNA is a good marker of HCV proliferation. Treatment with IFN is sometimes effective for seroconversion in HBV, and for eradication of virus in HCV.
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PMID:[Basic and clinical aspects of hepatitis virus carriers]. 880 69

Reverse transcription polymerase chain reaction (RT-PCR) has been used to detect hepatitis C virus (HCV) sequences in liver tissue. However, RT-PCR has a variable detection sensitivity, especially on routinely processed formalin-fixed, paraffin-embedded (FFPE) specimens. RNA-RNA and RNA-protein cross-links formed during formalin fixation is the major limiting factor preventing reverse trans criptase from extending the primers. To overcome this problem, we applied the ligation-dependent PCR (LD-PCR) for the detection of HCV RNA in FFPE liver tissue. This method uses two capture probes for RNA isolation and two hemiprobes for the subsequent PCR. Despite cross-links, the capture probes and the hemiprobes are able to form hybrids with HCV RNAs released from the FFPE tissue. The hybrids are isolated through binding of the capture probes to paramagnetic beads. The hemiprobes are then ligated by a T4 DNA ligase to form a full probe that serves as a template for the Taq DNA polymerase. A total of 22 FFPE liver specimens, 21 with hepatocellular carcinoma (HCC) and 1 with biliary cirrhosis secondary to bile duct atresia were selected for this study, of which 13 patients were HCV seropositive and 9 seronegative. HCV RNA was detectable by ID-PCR from all 13 HCV-seropositive HCCs and from 5 of 8 HCV-seronegative HCCs but not from the HCV-seronegative liver with biliary atresia. By contrast, RT-PCR detected HCV sequences in only 5 of the HCV-sero-positive and in 1 of the HCV-seronegative HCCs. To resolve the discordance between the LD-PCR and RT-PCR results, RT-PCR was performed on frozen liver tissue of the discrepant specimens, which confirmed the LD-PCR positive results. In conclusion, LD-PCR is a more sensitive method than RT-PCR for the detection of HCV sequences in routinely processed liver tissues. A high rate of HCV infection (86%) is found in HCC specimens, indicating a previously underestimated role of HCV in HCC pathogenesis.
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PMID:Detection of hepatitis C virus RNA using ligation-dependent polymerase chain reaction in formalin-fixed, paraffin-embedded liver tissues. 890 38

The human papillomavirus (HPV) E1 and E2 proteins bind cooperatively to the viral origin of replication (ori), forming an E1-E2-ori complex that is essential for initiation of DNA replication. All other replication proteins, including DNA polymerase alpha-primase (polalpha-primase), are derived from the host cell. We have carried out a detailed analysis of the interactions of HPV type 16 (HPV-16) E1 with E2, ori, and the four polalpha-primase subunits. Deletion analysis showed that a C-terminal region of E1 (amino acids [aa] 432 to 583 or 617) is required for E2 binding. HPV-16 E1 was unable to bind the ori in the absence of E2, but the same C-terminal domain of E1 was sufficient to tether E1 to the ori via E2. Of the polalpha-primase subunits, only p68 bound E1, and binding was competitive with E2. The E1 region required (aa 397 to 583) was the same as that required for E2 binding but additionally contained 34 N-terminal residues. In confirmation of these differences, we found that a monoclonal antibody, mapping adjacent to the N-terminal junction of the p68-binding region, blocked E1-p68 but not E1-E2 binding. Sequence alignments and secondary-structure prediction for HPV-16 E1 and other superfamily 3 (SF3) viral helicases closely parallel the mapping data in suggesting that aa 439 to 623 constitute a discrete helicase domain. Assuming a common nucleoside triphosphate-binding fold, we have generated a structural model of this domain based on the X-ray structures of the hepatitis C virus and Bacillus stearothermophilus (SF2) helicases. The modelling closely matches the deletion analysis in suggesting that this region of E1 is indeed a structural domain, and our results suggest that it is multifunctional and critical to several stages of HPV DNA replication.
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PMID:A C-terminal helicase domain of the human papillomavirus E1 protein binds E2 and the DNA polymerase alpha-primase p68 subunit. 969 37


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