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)

A 5 bp insertion was introduced into the BstEII site at nucleotide 2815 in DNA of hepatitis B virus (HBV) and a mutant HBV genome was produced, which coded for envelope and core proteins, but not for DNA polymerase, due to a frameshift. Cultured hepatoma cells (HepG2) were simultaneously transfected with a plasmid harbouring a tandem dimer of the mutant HBV DNA and another plasmid harbouring a tandem dimer of DNA of woodchuck hepatitis virus or duck hepatitis B virus. The replication of mutant HBV DNA, incapable of encoding DNA polymerase, was accomplished by cotransfecting woodchuck hepatitis virus DNA, but not by duck hepatitis B virus DNA. These results indicated a trans-complementation of the C and P genes in mammalian hepadnaviruses beyond a species barrier.
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PMID:Trans-complementation of the C gene of human and the P gene of woodchuck hepadnaviruses. 215 4

A viricide capable of eliminating hepatitis B virus (HBV) from chronic carriers should, theoretically, decrease the risk of primary hepatocellular carcinoma. Extracts of Phyllanthus amarus have been shown to inhibit the DNA polymerase of HBV and woodchuck hepatitis virus (WHV) in vitro. Three of four recently infected WHV carriers treated i.p. with P. amarus extract lost WHV, animals infected for greater than or equal to 3 months showed a decrease in virus levels. Preliminary results in human carriers treated orally with P. amarus for 1 month indicated that approximately 60% of the carriers lost HBV during the observation period.
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PMID:Hepatitis B virus and primary hepatocellular carcinoma: treatment of HBV carriers with Phyllanthus amarus. 215 92

An in vitro system for production of hepatitis B virus (HBV) was established by infection of human hepatoma (HepG2) cells. HBV particles obtained from the serum of a chronic hepatitis B surface antigen (subtype ad) carrier were used to inoculate HepG2 cells. HBV envelope and core proteins were synthesized de novo by the infected cells and secreted into the medium 3 to 6 days postinfection. Viral covalently closed circular DNA, the putative template for viral RNA transcription, accumulated in the cells with increasing time postinfection. The HBV-infected HepG2 cells were maintained for several months (HepG2-BV cell line) and continued producing viral antigens. Both HBV DNA replicative intermediates and major HBV transcripts were identified in HepG2-BV cells. Complete HBV particles, which contain HBV DNA and DNA polymerase activity and express the three antigenic specificities of the envelope (hepatitis B surface antigen, pre-S2, and pre-S1), were released into the culture supernatant. Thus, successful in vitro infection of transformed human hepatocytes raising stable HBV-producing cells was achieved for the first time. This strongly suggests that HepG2 cells have a receptor(s) for virus attachment and penetration. Such a system represents a significant advance for the study of HBV-target cell interactions as the early events of HBV infection.
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PMID:In vitro infection of human hepatoma (HepG2) cells with hepatitis B virus. 215 60

To analyze the process of liver regeneration and the initiation of hepatocellular carcinoma (HCC), we studied histochemically the morphologic features of proliferating parenchymal cells stained for DNA polymerase alpha (DPA), in 31 patients with various diseases, by use of a monoclonal antibody against DPA. In specimens from patients with acute viral hepatitis with confluent necrosis, most stained hepatocytes were small, with basophilic cytoplasm, and were located next to the necrotic areas. Under electron microscopy, stained granules were seen in the nucleus. Most stained hepatocytes had immature organelles. In specimens from patients with cirrhosis of the liver, the number of stained hepatocytes greatly differed in different pseudolobules. In specimens from patients with adenomatous hyperplasia, stained hepatocytes, mostly small and basophilic, were found diffusely; electron microscopy showed slightly indented nuclei with a few organelles and less condensed chromatin than normal. In specimens from patients with HCC, most stained cancer cells were small and basophilic; electron microscopy showed indented nuclei with a few organelles and less than normal condensed chromatin. Staining showed that during regeneration, immature hepatocytes reentered the cell cycle and repaired a large necrotic area. It was conceivable that in the initiation of HCC, some small hepatocytes with indented nuclei and less condensed chromatin might become HCC cells.
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PMID:Identification and fine structure of proliferating hepatocytes in malignant and nonmalignant liver diseases by use of a monoclonal antibody against DNA polymerase alpha. 221 Jul 24

Permanent murine fibroblasts (LTK-) were transfected with a dimer of hepatitis B virus (HBV) DNA and a neomycin resistance gene which were both linked to the simian virus 40 (SV40) early promoter/enhancer. One of the stably transfected clones, LTK4/36, which secreted HBsAg, HBeAg, and HBV DNA was further analyzed. It contained eight to nine copies of integrated HBV DNA per haploid genome and low amounts of episomal HBV DNA. The secreted viral DNA was covalently linked to protein and was associated with particles which had the characteristic density of natural virions from serum of human viremic carriers. The particles contained an endogenous DNA polymerase, small and middle surface proteins, but in contrast to natural virions very little core protein and large surface protein. Instead of core protein, they contained incompletely processed HBe protein which is colinear to core protein. The fibroblast-derived virions were less stable than virions from human carriers or from transfected hepatoma cells. After several days of storage, their DNA was only partially protected against DNase. Obviously, nonhepatic cells can express HBV-like particles, even if liver-dependent gene products like large surface protein and core protein are missing.
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PMID:Replication of hepatitis B virus in transfected nonhepatic cells. 221 25

Hepatitis B virus genome-transfected HepG2 cells (2.2.15 cells) inoculated into nude mice produced tumors within 2-8 wk. Dane particles, hepatitis B virus deoxyribonucleic acid polymerase activity, hepatitis B surface antigen, and hepatitis B e antigen were detected in the serum, and 36% of mice developed antibodies to hepatitis B core antigen. In the tumors, hepatitis B surface, core, and e antigens were observed by electron microscopy and immunoenzymatic techniques. In-situ hybridization and Southern blot analysis showed hepatitis B virus deoxyribonucleic acid in the tumor. Tumors could be propagated by injection of minced tumor tissue or of a tumor-derived cell line. Liver of tumor-bearing mice as well as sera and tissues of mice inoculated with control cell lines did not show hepatitis B virus genome or viral markers. Tumors induced by both 2.2.15 and nontransfected HepG2 cells exhibited myc oncogene protein and various hepatoma-associated antigens (alpha-fetoprotein, alpha-1-antitrypsin, alpha-1-antichymotrypsin, carcinoembryonic antigen, cytokeratin), suggesting that viral formation does not interfere with expression of these antigens. This experimental model will be helpful to study the effect of drugs on in-vivo hepatitis B virus replication and viral antigen expression.
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PMID:A nude mouse model for the in vivo production of hepatitis B virus. 229 3

We have studied antibodies (anti-pol antibody) against the polymerase gene product of hepatitis B virus by solid-phase enzyme immunoassay using synthetic peptides coded for by this gene. Sera from six patients with acute hepatitis B, 112 chronic hepatitis B virus carriers and six healthy individuals with naturally acquired immunity to hepatitis B virus were tested for anti-pol antibody. In acute hepatitis B virus infection, anti-pol antibody was detected in three of six patients. In chronic hepatitis B virus infection, anti-pol antibody was detected in 17 of 29 (59%), in 23 of 33 (70%) of cirrhotic patients and in 18 of 24 (75%) patients with cirrhosis complicated by hepatocellular carcinoma, compared with 4 of 19 (21%) asymptomatic carriers and 2 of 7 (29%) patients with chronic persistent hepatitis. Titers of anti-pol antibody were higher in cirrhotic patients with and without hepatocellular carcinoma than in patients with chronic active hepatitis. The presence of anti-pol antibody, however, had no relationship with hepatitis B virus-associated DNA polymerase activities and other viral replicative markers. As for sera from six healthy individuals with naturally acquired immunity to hepatitis B virus, two (33%) were positive for anti-pol antibody. These results indicate that the immune response toward the polymerase gene product is induced during acute and chronic hepatitis B virus infection. In chronic hepatitis B virus infection, anti-pol antibody may serve as a new marker indicative of a long period of hepatitis B virus-induced hepatitis.
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PMID:Detection of antibodies against the polymerase gene product in hepatitis B virus infection. 239 Oct 62

The effects of suramin, an antiparasitic agent, upon in vitro hepatitis B surface antigen production by the human hepatoma cell line PLC/PRF/5 and hepatitis B virus associated DNA polymerase activity in the serum of a chronically infected patient were examined. Treatment with suramin resulted in decreases in hepatitis B surface antigen production and hepatitis B-virus associated DNA polymerase activity. The decrease in hepatitis B surface antigen production was paralleled by a general decrease in hepatoma cell viability and cellular protein synthesis. Although the inhibitory effects of suramin for hepatitis B virus appear to be nonspecific as demonstrated in these two in vitro systems, the recently announced trial of suramin for the treatment of the acquired immunodeficiency syndrome should afford an unusual opportunity to evaluate the effectiveness of suramin in the treatment of chronic hepatitis B virus infection.
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PMID:Effects of suramin on in vitro HBsAg production by PLC/PRF/5 cells and hepatitis B virus DNA polymerase activity. 242 68

An uncontrolled pilot study of adenine arabinoside monophosphate intramuscularly (ARA-AMP) for 5 days at 10 mg/kg/day and 23 days at 5 mg/kg/day in divided doses, was conducted in 15 consecutive patients known to be HBeAg-positive for a minimum of 12 months. Two patients were lost to follow-up (1 having developed an hepatoma). Of the remaining 13, 11 remained HBeAg-positive at 1 year. During treatment, the median serum DNA polymerase (DNAp) activity fell from 592 cpm to 203 cpm/200 microliters. Of 12 patients initially positive for DNA polymerase, complete inhibition during treatment occurred in 6 and was permanent in 2, who developed anti-HBe. In the remaining 4 and in 6 further patients in whom inhibition was substantial but incomplete, DNAp activity rose to pretreatment levels within 1 month of completing treatment. All these patients remained DNAp + HBeAg-positive at one year. Serum HBV-DNA was measured in 7 patients, 6 who were initially DNAp-positive and 4 of whom had complete inhibition of DNAp during treatment. All 7 remained positive for HBV-DNA during treatment. Although side-effects were common there were no significant changes in biochemical or haematological parameters during or subsequent to therapy. Over the subsequent 48 months 2 more patients have developed an hepatoma and a further 5 have lost HBeAg; the 4 patients who remain alive and HBeAg-positive all had chronic persistent hepatitis initially.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Differential effect of ARA-AMP on serum DNA polymerase activity and serum HBV-DNA in chronic hepatitis B virus infection. A possible reason for lack of efficacy. 243 80

Recent studies suggest that hepatitis B virus (HBV), despite being a DNA virus, replicates via an RNA intermediate (R. H. Miller, P. L. Marion, and S. W. Robinson, Virology 139:64-72, 1984; J. Summers and W. S. Mason, Cell 29:403-415, 1982). The HBV life cycle is therefore a permuted version of the RNA retroviral life cycle. Sequence homology between retroviral reverse transcriptase and the putative HBV polymerase gene product suggests the presence of an HBV reverse transcriptase (H. Toh, H. Hajashida, and T. Miyata, Nature (London) 305:827-829, 1983). As yet, there has been no direct evidence that reverse transcriptase activity is present in the viral particle. We used activity gel analysis to detect the in situ catalytic activities of DNA polymerases after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Our studies demonstrated that HBV-like particles secreted by a differentiated human hepatoma cell line transfected with genomic HBV DNA contain two major polymerase activities which migrate as approximately 90- and approximately 70-kilodalton (kDa) proteins. This demonstrated, for the first time, that HBV-like particles contain a novel DNA polymerase-reverse transcriptase activity. Furthermore, we propose that the 70-kDa reverse transcriptase may be produced by proteolytic self-cleavage of the 90-kDa precursor protein.
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PMID:Two proteins with reverse transcriptase activities associated with hepatitis B virus-like particles. 244 93


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