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At least 19 recordsLinked to original sources
PubMed1998

Inhibition of tumor necrosis factor and interferon triggered responses by DNA viruses.

DNA viruses use elegant mechanisms to overcome the antiviral responses mediated by tumor necrosis factor (TNF), the TNF receptor family member Fas and the interferons. TNF, which is secreted by activated monocytes and lymphocytes, induces apoptosis as well as expression of genes involved in the inflammatory and immune responses. Depending on the DNA virus and the viral proteins, the following mechanisms to prevent TNF receptor- and Fas-induced apoptosis are used: (1) absorption of extracellular TNF by secreted homologs of the TNF receptor; (2) degradation of Fas; (3) inhibition of the assembly of FADD and Caspase 8 with TNFR1 and Fas; (4) direct inhibition of proapoptotic caspase enzymatic activity; and (5) inhibition of the proapoptotic members of the Bcl-2 family. Interferons induce expression of multiple antiviral genes. DNA viruses encode proteins that function in different ways to block interferon-induced transcription as well as the activity of enzymes that block viral protein synthesis. These antiviral proteins prolong acute and persistent infections.

Animals↗
PubMed1984

RNA tumor viruses, DNA tumor viruses and developmental switches: a unifying hypothesis.

It is hypothesized that oncogenic viruses (both RNA and DNA tumor viruses) use cellular differentiation switches as part of their mechanism for viral replication. Chemical or radiation-induced carcinogenesis is the result of mutations which also affect these differentiation switches and their cellular controls. A transformed cell is characterized by the uncontrolled and inappropriate expression of embryonic (developmental) sequences. Many of the oncogenic viruses, both RNA and DNA, are lineage- and stage-specific in the cells they can productively infect, in keeping with their means of replication. The interaction between virus and host cellular controls determines whether recognizable neoplasia will result from viral infection.

Animals↗
PubMed2006

Double-stranded RNA is produced by positive-strand RNA viruses and DNA viruses but not in detectable amounts by negative-strand RNA viruses.

Double-stranded RNA (dsRNA) longer than 30 bp is a key activator of the innate immune response against viral infections. It is widely assumed that the generation of dsRNA during genome replication is a trait shared by all viruses. However, to our knowledge, no study exists in which the production of dsRNA by different viruses is systematically investigated. Here, we investigated the presence and localization of dsRNA in cells infected with a range of viruses, employing a dsRNA-specific antibody for immunofluorescence analysis. Our data revealed that, as predicted, significant amounts of dsRNA can be detected for viruses with a genome consisting of positive-strand RNA, dsRNA, or DNA. Surprisingly, however, no dsRNA signals were detected for negative-strand RNA viruses. Thus, dsRNA is indeed a general feature of most virus groups, but negative-strand RNA viruses appear to be an exception to that rule.

Animals↗
PubMed1996

Ligation of double-stranded and single-stranded [oligo(dT)] DNA by vaccinia virus DNA ligase.

Vaccinia virus DNA ligase has been expressed in Escherichia coli, purified, and biochemically characterized. The enzyme ligates double-stranded (ds) DNA substrates with either cohesive or blunt-end termini and the latter reaction is stimulated by PEG. Vaccinia virus DNA ligase can also ligate oligo(dT) when annealed to either a poly(dA) or a poly(rA) backbone and, remarkably, free oligo(dT). This ligation of a single-stranded (ss) substrate is unique among eukaryotic DNA ligases. The enzyme requires high ATP concentrations with a Km for the overall ligation of a ssDNA substrate of 0.8 mM. The salt, divalent cation, temperature, and pH requirements of the enzyme for the optimal ligation of ss and ds substrate are described.

Adenosine Triphosphate↗
PubMed2006

Inhibition of PKR by RNA and DNA viruses.

Interferons were the first of the anti-viral innate immune modulators to be characterized, initially characterized solely as anti-viral proteins [reviewed in Le Page, C., Genin, P., Baines, M.G., Hiscott, J., 2000. Inteferon activation and innate immunity. Rev. Immunogenet. 2, 374-386]. As we have progressed in our understanding of the interferons they have taken a more central role in our understanding of innate immunity and its interplay with the adaptive immune response. One of the key players in function of interferon is the interferon-inducible enzyme, protein kinase (PKR, activatable by RNA). The key role played by PKR in the innate response to virus infection is emphasized by the large number of viruses, DNA viruses as well as RNA viruses, whose hosts range from insects to humans, that code for PKR inhibitors. In this review we will first describe activation of PKR and then describe the myriad of ways that viruses inhibit function of PKR.

Animals↗
PubMed1978

Induction of infectious virus DNA and virus particles by mitomycin C in SV40-transformed mouse cells.

A line of SV40-transformed mouse cells (SV/3T3-4E) was isolated and four clones were derived from this line. Spontaneous production of small amounts of infectious SV40 DNA was detected in the parental line and in three out of the four clones tested, although no synthesis of virions could be demonstrated. The yields of SV40 DNA were significantly enhanced following treatment of these cells with mitomycin C and infectious virus particles became detectable occasionally.

Cell Line↗
PubMed1982

Transformation of human embryonic fibroblasts by BK virus, BK virus DNA and a subgenomic BK virus DNA fragment.

Human embryonic fibroblasts (HEF) have been transformed by BK virus (BKV) DNA and by u.v.-inactivated or live BKV alone or in association with methyl-cholanthrene (MTC). The transformed cells produced BKV large T and small t antigens as well as the cellular 53 kdal protein, detected by immunofluorescence and immunoprecipitation. After an initial phase of lysis and virus shedding, virus or its coat protein antigen could not be detected in transformed cells. All human transformed cell lines could be superinfected by BKV or BKV DNA, but their susceptibility to superinfection was 20- to 500-fold lower than normal HEF. BKV could be rescued by fusion of transformed cells with normal HEF or Vero cells and by transfection of normal HEF with total DNA and DNA extracted from the Hirt supernatant of transformed cells. Blot hybridization analysis of DNA from transformed cells showed a considerable amount of free BKV DNA in monomeric and polymeric forms. Integrated BKV DNA was absent in most cell lines but present in only small amounts in BKV-transformed cells treated with MTC. Analysis of free BKV DNA with various restriction endonucleases and by blot hybridization showed that monomeric forms were complete BKV genomes, whereas polymers contained both complete and defective or rearranged BKV DNA. Transformation of HEF was also obtained with a 3.7 kilobase (kb) fragment of the BKV genome, produced by sequential digestion of BKV with the restriction endonucleases HhaI and EcoRI. This fragment extends clockwise on the virus genome from 0 to 72.2 map units and contains the entire early region. Blot hybridization analysis of cells transformed by the HhaI/EcoRI 3.7 kb fragment showed two separate integrations of BKV sequences without free virus DNA.

Antigens, Viral↗
PubMed1990

Phosphonylmethoxyalkyl derivatives of purine as inhibitors of human hepatitis B virus DNA synthesis.

A selected number of antiviral compounds which have been previously shown to inhibit the replication of DNA viruses or retroviruses were examined for their inhibitory effects on human hepatitis B virus (HBV) DNA synthesis. The assay system was based on the use of a human hepatoblastoma cell line (HB611) that continuously synthesizes HBV DNA. The following phosphonylmethoxyalkyl-purine derivatives were found to inhibit HBV DNA synthesis: 9-(2-phosphonyl-methoxyethyl)-2',6'-diaminopurine (PMEDAP), (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (HPMPA) and 9-(2-phosphonylmethoxyethyl)adenine (PMEA). PMEDAP, HPMPA and PMEA not only inhibit HBV DNA synthesis in HB611 cells but also duck hepatitis B virus (DHBV) DNA and core antigen synthesis in primary duck hepatocytes.

Adenine↗
PubMed1998

Detection of sequences of TT virus, a novel DNA virus, in German patients.

Recently a novel DNA virus, designated TT virus (TTV), that possibly accounts for some of the cases of liver disease of unknown aetiology, was identified in Japanese patients. Using specific primer pairs for conserved regions, we detected TTV DNA by PCR in 16/84 (19%) German patients awaiting orthotopic liver transplantation because of decompensated liver cirrhosis (of diverse causes); in 4/25 (16%) patients with non-A-G hepatitis; in 1/7 patients with autoimmune hepatitis; and in one intravenous drug user. Sequence analysis showed that in contrast to the findings in Japanese patients only about 37% of our TTV sequences belonged to genomic group 1 but about 58% belonged to group 2, including several sequences belonging to a further subgroup tentatively designated group 2c. Further studies to clarify whether the novel virus has hepatitis-inducing capacity or other clinical significance are needed.

Amino Acid Sequence↗
PubMed1988

Inhibition of human hepatitis B virus DNA polymerase and duck hepatitis B virus DNA polymerase by triphosphates of thymidine analogs and pharmacokinetic properties of the corresponding nucleosides.

Replication of hepadnaviruses involves a viral DNA polymerase containing both a DNA-dependent and an RNA dependent activity. This polymerase is a potential target for chemotherapy against hepatitis B. We have used human hepatitis B virus DNA-dependent DNA polymerase from human serum and duck hepatitis B virus DNA-dependent DNA polymerase from duck serum as well as RNA-dependent DNA polymerase activity from duck hepatitis B-infected duck liver. Triphosphates of thymidine analogs have been synthesized and tested for their inhibitory activities against these enzymes with the intention both to explore differences between these enzymes and structural requirements for inhibitors. The results showed that with the inhibitors tested, hepatitis B virus DNA-dependent DNA polymerase was the most sensitive enzyme and the triphosphate of 5-propenyl-2'-deoxyuridine was the most active inhibitor. In addition, the 5'-triphosphate of 5-propenyl-arabinofuranosyluracil also inhibited the hepadnavirus DNA-dependent DNA polymerases, and was a competitive inhibitor with respect to 2'-deoxythymidine triphosphate as showed by kinetic studies with duck hepatitis B virus DNA-dependent DNA polymerase from serum. Pharmacokinetic analysis showed 5-propenyl-2'-deoxyuridine to be well absorbed orally, but rapidly cleared from plasma. The arabinofuranosyl analog was also well absorbed but cleared less rapidly. Hence, these results indicate the potential of 5-propenyl-2'-deoxyuridine and 5-propenyl-arabinofuransyluracil for chemotherapy of hepatitis B.

Animals↗
PubMed1999

[Detection of TT virus DNA in patients with non-A to G liver diseases].

A novel single-stranded DNA virus, TT virus(TTV), has been reported recently. We detected TTV viral sequences by polymerase chain reaction using primers derived from nucleotide sequences of ORF1 and the 5' noncoding region of ORF2. Using primers of the 5' noncoding region, TTV DNA was detected in 21 of 25(84%) healthy individuals, suggesting that most TTV strains detected by these primers are almost harmless. In contrast, using primers of ORF1, which detect genotype 1a TTV that was reported to be a causative agent of posttransfusion hepatitis, TTV DNA was detected in only 3 of 25 healthy subjects and 3 of 27 acute and 9 of 72(12%) chronic non-A to G hepatitis patients. Whether these TTV strains actually cause hepatitis remains to be determined.

Biomarkers↗
PubMed2000

Investigation of the association between infection with Helicobacter pylori and with TT virus, a novel DNA virus, in patients with gastroduodenal ulcer or ulcer scar.

OBJECTIVE: Recently, a novel DNA virus (TT virus; TTV) has been isolated. Enteric transmission is suggested as a route of transmission of TTV, with high prevalence of this virus infection in the general population, and age and geographical distributions of TTV prevalence very similar to those of Helicobacterpylori infection. We analysed an association between TTV and H. pylori infection in patients with gastroduodenal ulcer or ulcer scar. METHODS: In 181 patients with a gastroduodenal ulcer or ulcer scar (102 with a gastric lesion, 60 with a duodenal lesion, and 19 with both sites involved), specimens were cultured for H. pylori and TTV infection was sought in serum by a polymerase chain reaction. RESULTS: H. pylori infection was demonstrated in 152 patients (84.0%) and TTV was detected in 168 patients (92.8%). Patients with TTV were significantly older than those without TTV (P = 0.0001), while no age difference was observed between patients with and without H. pylori infection. No difference was apparent in the prevalence of TTV infection between patients with and without H. pylori infection, and vice versa. CONCLUSIONS: We found no association between TTV infection and H. pylori infection in patients with peptic ulcer diseases, which is consistent with a lack of association between TTV infection and peptic ulcer. However, larger studies including surveys of the general population will be required to analyse the overall association between TTV and H. pylori.

Adult↗
PubMed1991

Rice tungro bacilliform virus DNA independently infects rice after Agrobacterium-mediated transfer.

In nature, rice tungro disease is caused by an RNA and a DNA virus complex, but we have obtained an independently infectious clone of rice tungro bacilliform virus (RTBV) DNA. Infectivity could be demonstrated only when a more than unit-length copy was cloned in the Agrobacterium binary vector Bin 19 and agroinoculated into rice plants. Rice plants thus agroinfected with cloned RTBV DNA showed typical symptoms of tungro disease, presence of viral DNA and bacilliform particles, and could be used as a source of virus to infect healthy plants by the green leafhopper (Nephotettix virescens). The importance of this infectious clone in understanding the molecular biology of RTBV and the rice tungro disease is discussed.

DNA, Viral↗
PubMed2006

Interactions between DNA viruses, ND10 and the DNA damage response.

ND10 are small nuclear substructures that are defined by the presence the promyelocytic leukaemia protein PML. Many other proteins have been detected within ND10, a complexity that is reflected in reports of their involvement in multiple cellular pathways that include the regulation of gene expression, chromatin dynamics, protein modification, apoptosis, p53 function, senescence, DNA repair, the interferon response and viral infection. This review summarizes recent evidence of similarities between the behaviour of ND10 components and DNA repair pathway proteins in response to viral infection and DNA damage. ND10 structures become associated with the parental genomes and early replication compartments of many DNA viruses, and DNA repair pathway proteins are also recruited to these sites. Similarly, PML and DNA repair proteins are recruited to sites of DNA damage. The mechanisms by which these events might occur, and the implications for ND10 function in DNA virus infection and chromatin metabolism, are discussed.

Animals↗
PubMedDate not supplied

Changes of hepatitis B virus DNA in liver and serum caused by recombinant leukocyte interferon treatment: analysis of intrahepatic replicative hepatitis B virus DNA.

Twenty patients with HBeAg-positive chronic liver disease were given large doses of recombinant leukocyte interferon for 4 weeks. Changes of hepatitis B virus DNA in livers and sera were analyzed by the molecular hybridization technique in paired biopsies obtained before and 2 weeks after treatment. Serum hepatitis B virus DNA was examined before, during and after the treatment until 4 weeks post-interferon. Analysis of hepatic hepatitis B virus DNA revealed species that appeared to represent various forms of replicative hepatitis B virus DNA, i.e., relaxed circular, linear, supercoiled and single-stranded hepatitis B virus DNA, respectively. No evidence of integration of hepatitis B virus DNA in genomic DNA was obtained. Of 15 cases which were positive for hepatic hepatitis B virus DNA before treatment and in which paired biopsies were obtained, hepatic hepatitis B virus DNA became negative in 4, decreased in 5 and unchanged in 6. Among several types of replicative viral DNA in liver tissue, supercoiled hepatitis B virus DNA tended to remain after other forms were reduced. A close correlation between hepatic and serum hepatitis B virus DNA was found in 37 liver biopsy samples and corresponding sera. These results indicate that interferon treatment reduces serum hepatitis B virus levels by inhibiting viral replication in the liver and that persistence or reappearance of hepatitis B virus in serum after interferon is associated with replication.

Adult↗
PubMed2001

Existence of TT virus DNA and TTV-like mini virus DNA in infant cord blood: mother-to-neonatal transmission.

The route of transmission of TT virus (TTV) was studied by examining the existence of TTV DNA in different body fluids from the new born infants and their mothers. A total of 52 pregnant women with normal serum alanine aminotransferase levels were enrolled in this study. TTV DNA was examined using a polymerase chain reaction method using Takahashi's primers which can detect all genotypes of TTV and Okamoto's primers which detect only some of the genotypes of TTV. TTV DNA was detected in the sera from 40/52 (77%), in the breast milk from 35/52 (67%), and in the amniotic fluid from 6/6 (100%) pregnant mothers using Takahashi's primers TTV DNA was also detected in the sera from 8 of 11 (73%) and in the cord blood from 25/52 (48%) new born infants using Takahashi's primers. However, TTV DNA was detected in only 5/52 maternal blood (10%) and 4/52 breast milk (8%) using Okamoto's primers. All samples positive for TTV DNA by Takahashi's primers, were also positive for TTV-like mini virus (TLMV) DNA. Our data suggest that intrauterine transmission or transmission via breast milk may contribute to maintaining the global TTV and TLMV reservoir.

Journal Article↗