Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The accepted model of retroviral reverse transcription includes a circular DNA intermediate which requires strand displacement synthesis for linearization and creation of an integration-competent, long terminal repeat-flanked DNA product. We have used an in vitro model of this last step of reverse transcription to examine the role of the viral enzyme, reverse transcriptase (RT), in displacement synthesis. We show that Moloney murine leukemia virus RT possesses an activity which allows for displacement synthesis through a minimum of 1,334 bp of duplex DNA--an extent much greater than that required during in vivo reverse transcription and over 25-fold greater than has been previously demonstrated for a viral RT. RT does not function as a helicase in the classical sense but appears to closely couple duplex DNA melting with synthesis-driven translocation of the enzyme. In the absence of synthesis, the unwound region created by a primer-positioned RT appears to be no greater than 2 bp and does not advance along the template. Additionally, RT does not utilize ATP or any deoxynucleoside triphosphate not directly encoded by the template strand to catalyze processive duplex unwinding at a nick; nor does binding of the enzyme unwind duplex DNA in the absence of a 3' terminus. The approximate maximum chain elongation rate during strand displacement synthesis by Moloney murine leukemia virus RT falls between 0.73 and 1.5 nucleotides per s at 37 degrees C. The RNase H activity of RT does not appear to play a role in displacement synthesis; however, a 181-amino-acid C-terminal truncation of RT displays a dramatically reduced ability to catalyze synthesis through duplex DNA.
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PMID:Strand displacement synthesis capability of Moloney murine leukemia virus reverse transcriptase. 751 25

The San Miguel sea-lion viruses (SMSV) and vesicular exanthema of swine viruses (VESV) are members of the calicivirus family and aetiologic agents of vesicular disease in susceptible hosts. These two virus groups have been shown by several serological methods to be closely related antigenically. To further examine their relatedness, two sets of non-degenerate oligonucleotide primers were designed for the specific amplification of two distinct regions of the SMSV and VESV genomes using a reverse transcriptase-polymerase chain reaction (RT-PCR) protocol. The sequence of the primers were based on the nucleotide sequence of SMSV serotypes 1 and 4. The RNAs from a number of SMSV serotypes and a single VESV isolate were used as template in this study. These included SMSV serotypes 1, 2, 4, 5, 6, 7, 13 and 14 and VESV serotype A48. Also included in this study were Tillamook calicivirus (Bos-1 calicivirus, BCV) and a recently isolated skunk calicivirus (SCV). The first primer set amplified a 357-bp fragment from the 2C-like or RNA-helicase-encoding region (11 of 11 viruses) and the second set amplified a fragment from the RNA-dependent RNA polymerase region (520 bp, 9 of 11 viruses). These primer sets did not amplify product from either feline calicivirus or mink calicivirus. The results of this study demonstrate the genetic relatedness of SMSV and VESV and the potential usefulness of RT-PCR to detect and identify these viruses in diagnostic and routine screening applications.
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PMID:Development of PCR primers for specific amplification of two distinct regions of the genomes of San Miguel sea-lion and vesicular exanthema of swine viruses. 776 Aug 57

In 1995, a new human hepatitis virus belonging to the family Flaviviridae was described and designated hepatitis GBV-C. To investigate variations within the genome of GBV-C and to study the relationship of GBV-C to GBV-A/B or hepatitis C virus (HCV), we established a detection system using reverse transcriptase polymerase chain reaction (RT-PCR) of the putative helicase region (NS3). So far, isolates derived from 14 different GBV-C-positive sera were analyzed (GBV-C/S3-36), showing 80.1-89.4% (mean: 85%) identical nucleotides. The deduced amino acid sequences revealed 97.3% homology. Nucleotide sequences of GBV-C/S3-36 revealed about 60% identity to GBV-A as well as to HCV, but only 56% identity to GBV-B. Amino acid sequences revealed 73.4 and 68.6% similarity to GBV-A and GBV-B, respectively, but a slightly higher percentage of 78.5% to HCV sequences. Thus, according to the putative GBV-C helicase sequence, a subtyping of GBV-C into different genotypes may be necessary.
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PMID:Sequence analysis of hepatitis GB virus C (GBV-C) isolates from 14 patients. 902 80

We investigated the possible role of hepatitis G virus (HGV or GBV-C) in the aetiology of acute non-A-E hepatitis in Argentina by detecting viral RNA in sera by reverse transcriptase-polymerase chain reaction (RT-PCR) using primers specific for the putative NS3 helicase region of HGV. Sixty two patients with acute hepatitis were included in this study. The absence of hepatitis A-E was confirmed by serological testing, and all patients were negative for HCV RNA and autoimmune markers. All patients denied alcohol intake and the use of hepatotoxic drugs. Their mean age was 35.3 years and 37 were males. HGV RNA was present in 19/62 (30.6%) of the patients with non-A-E acute hepatitis. Among HGV-positive patients, three had parenteral risk factors within 3 months of onset, one was a health care worker, one was sexually promiscuous, one had travelled to the Middle East and 13 (68.4%) had no history of parenteral exposure. Epidemiological, clinical and biochemical features between HGV-positive and negative patients did not achieve statistical significance. Hence, HGV appears to play a role in the pathogenesis of acute viral hepatitis; however, the etiology of a significant number of hepatitis cases remains unclear, suggesting the existence of an additional agent(s). The absence of parenteral exposure in most of the HGV RNA-positive patients in this study shows that routes of community-acquired HGV infection are not yet completely understood.
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PMID:Detection of hepatitis G virus RNA in patients with acute non-A-E hepatitis. 965 68

Recently, two new flaviviruses, GB virus A (GBV-A) and GB virus B (GBV-B), were identified in the plasma of a tamarin infected with the hepatitis GB agent. A third virus, GB virus C (GBV-C), was subsequently identified in humans. In the current study, representational difference analysis (RDA) was used to search for a new virus in the serum of a chimpanzee that developed acute resolving hepatitis following inoculation with a pool of chimpanzee plasma. The plasma pool originated from serial passages of a human sample containing virus-like particles. Numerous cDNA clones were obtained that exhibited 62-80% identity with GBV-C. With the exception of the extreme 5' and 3' ends, the complete viral genome was sequenced, revealing a single large open reading frame encoding a 2833 amino acid polyprotein that contains two envelope proteins, two proteases, a helicase, and an RNA-dependent RNA polymerase. Phylogenetic analysis of the new virus indicates that it is closely related to GBV-C, yet still sufficiently divergent as to be placed in a separate group, tentatively labeled GB virus Ctroglodytes (GBV-Ctro). Numerous human samples were screened by reverse transcriptase-polymerase chain reaction (RT-PCR), but GBV-Ctro sequence was not detected. However, a second chimpanzee inoculated with the same plasma pool was shown to develop a GBV-Ctro infection. Although isolated from an Old World primate with hepatitis, the primary host of GBV-Ctro and any association with disease remains to be determined.
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PMID:Isolation of a GB virus-related genome from a chimpanzee. 970 Jun 32

A monoclonal antibody (mAb) that reacted specifically with a 16 kDa big liver and spleen disease virus (BLSV) protein was used to identify the protein in western immunoblots of infected liver extracts and enable partial amino acid sequence analysis of the protein. Based on this sequence, a degenerate primer was designed that was used in conjunction with random hexamers in a reverse transcriptase-POR (RT PCR), to amplify a 523 bp product from RNA extracted from homogenates of BLSV-infected livers. There was 62% nucleotide sequence identity between this sequence and the sequence of the helicase gene of human hepatitis E virus (HEV). POR primers designed from this 523 bp fragment were able to amplify a 490 bp product from livers of virus-infected chickens but not chickens from virus-free flocks.
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PMID:Sequence data suggests big liver and spleen disease virus (BLSV) is genetically related to hepatitis E virus. 1050 Nov 68

Nitric oxide (NO) is considered an important signaling molecule implied in various different physiological processes, including nervous transmission, vascular regulation, and immune defence, as well as the pathogenesis of several diseases. NO reportedly also has an antiviral effect on several DNA and RNA virus families. The NO-mediated S-nitrosylation of viral and host (macro)molecules appears to be an intriguing general mechanism for the control of the virus life cycle. In this respect, NO is able to nitrosylate cysteine-containing enzymes (e.g., proteases, reverse transcriptase, and ribonucleotide reductase). Moreover, zinc-fingers and related domains present in enzymes (e.g., HIV-1-encoded integrase or herpes simplex virus type-1 heterotrimeric helicase-primase complex) or nucleocapsid proteins may be considered as NO targets. Also, NO may regulate both host (e.g., nuclear factor-kappaB) and viral-encoded (e.g., HIV-1 tat protein or Epstein-Barr virus Zta) transcriptional factors that are involved in virus replication. Finally, NO-mediated S-nitrosylation of cysteine-containing glycoproteins and hemagglutinin may also occur. Here, NO targets are summarised, and the molecular bases for the antiviral effect of NO are discussed.
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PMID:S-nitrosylation of viral proteins: molecular bases for antiviral effect of nitric oxide. 1079 12

WRN encodes a RecQ helicase, which is mutated in Werner syndrome. Werner syndrome is a genetic condition of young adults characterized by premature aging, limited replicative capacity of cells in vitro, and increased cancer risk. Telomerase is a reverse transcriptase that extends the G-rich strand of telomeric DNA. Primary cells in vitro typically lack telomerase activity and undergo senescence, whereas telomerase is reactivated in many, but not all, tumors. The roles of the two genes are not known to be related. Here we report the development of an effective colony-forming assay in which a SV40-transformed Werner fibroblast cell line is 6-18-fold more sensitive to 4-nitroquinoline 1-oxide than SV40-transformed normal cell lines. The sensitivity can be partially reversed by transfecting a normal WRN gene but not a mutated WRN gene into the cells. Curiously, the sensitivity can be reversed equally well by transfecting a telomerase gene (TERT) into the cells. These data indicate the possibility of an interdependent function of these two genes.
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PMID:WRN or telomerase constructs reverse 4-nitroquinoline 1-oxide sensitivity in transformed Werner syndrome fibroblasts. 1081 Nov 12

G-Quadruplex DNAs are folded, non-Watson-Crick structures that can form within guanine-rich DNA sequences such as telomeric repeats. Previous studies have identified a series of trisubstituted acridine derivatives that are potent and selective ligands for G-quadruplex DNA. These ligands have been shown previously to inhibit the activity of telomerase, the specialized reverse transcriptase that regulates telomere length. The RecQ family of DNA helicases, which includes the Bloom's (BLM) and Werner's (WRN) syndrome gene products, are apparently unique among cellular helicases in their ability to efficiently disrupt G-quadruplex DNA. This property may be relevant to telomere maintenance, since it is known that the sole budding yeast RecQ helicase, Sgs1p, is required for a telomerase-independent telomere lengthening pathway reminiscent of the "ALT" pathway in human cells. Here, we show that trisubstituted acridine ligands are potent inhibitors of the helicase activity of the BLM and WRN proteins on both G-quadruplex and B-form DNA substrates. Inhibition of helicase activity is associated with both a reduction in the level of binding of the helicase to G-quadruplex DNA and a reduction in the degree to which the G-quadruplex DNA can support DNA-dependent ATPase activity. We discuss these results in the context of the possible utility of trisubstituted acridines as antitumor agents for the disruption of both telomerase-dependent and telomerase-independent telomere maintenance.
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PMID:Inhibition of the Bloom's and Werner's syndrome helicases by G-quadruplex interacting ligands. 1173 2

Diisononyl phthalate (DINP) is a compound widely used as a plasticizer in the production of polyvinyl chloride products. Chronic exposure to DINP leads to liver cancer in rats and mice. Many phthalates are considered to be relatively weak peroxisome proliferators (PP), a group of rodent hepatocarcinogens that cause a variety of adaptive responses in liver through the PP-activated receptor alpha (PPARalpha). The objectives of this study were to determine whether DINP-induced effects in the liver associated with carcinogenesis are mediated by PPARalpha and to identify novel gene targets of DINP. Male and female SV129 wild-type, SV129 PPARalpha-null, and B6C3F1 mice were administered DINP by gavage or in the feed. Transcript profile technology and reverse transcriptase (RT)-polymerase chain reaction (PCR) were used to identify gene targets. Dose-dependent increases in relative liver weights were dependent on PPARalpha in 10- or 12-week-old male and female mice and 30-week-old male mice. Female 30-week-old mice exhibited PPARalpha-independent increases in relative liver weights. Increases in hepatocyte proliferation, palmitoyl-CoA oxidase (PCO) activity, and levels of enzymes involved in beta- and omega-oxidation of fatty acids were shown to be dependent on PPARalpha. Five novel genes were shown to be altered in the livers of female wild-type mice after a 3-week exposure, but not in PPARalpha-null, mice. These genes included those involved in DNA repair and recombination (ATP-dependent helicase and Endonuclease III homolog), drug metabolism (Cyp2a4) and protein trafficking (FKBP-1, FKBP-13). An additional gene (Cyp2d9) was shown to be down-regulated in wild-type mice but up-regulated in PPARalpha-null mice indicating more complex regulation by PPARalpha and additional factors. These data support the hypothesis that PPARalpha plays a dominant role in mediating the effects associated with hepatocarcinogenesis after DINP exposure.
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PMID:Role of the peroxisome proliferator-activated receptor alpha in responses to diisononyl phthalate. 1296 24


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