Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.7 (DNA polymerase)
 17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

9-beta-D-Arabinofuranosyladenine 5'-triphosphate (ara-ATP) is an inhibitor both of DNA polymerase-alpha and -beta from noninfected rabbit kidney cells and of the DNA-dependent DNA polymerase induced by herpes simplex virus Type 1 (strain IES). The studies were performed with partially purified enzymes, and each of the different polymerase preparations contained only one DNA-dependent DNA polymerase species. These enzymes were inhibited in a competitive manner. The HSV-induced DNA-dependent DNA polymerase was 39-fold more sensitive to ara-ATP than was cellular DNA polymerase-beta and 116-fold more sensitive than cellular DNA polymerase-alpha. The affinity of the HSV-induced enzyme for ara-ATP was only slightly influenced by the use of different template/initiators in the enzyme assays. In intact cell systems DNA synthesis was affected by 9-beta-D-arabinofuranosyladenine (ara-A) as indicated by the reduced incorporation of deoxythymidine. In herpesvirus-(strain Lennette)-infected cells, however, ara-A shows no influence on the incorporation on deoxythymidine into cellular DNA, but it substantially reduces the incorporation into viral DNA. Ara-A itself is incorporated into both cellular and herpesviral (strain Lennette, D-316 and IES) DNA during DNA synthesis.
 ...
PMID:Inhibition of herpesvirus DNA synthesis by 9-beta-D-arabinofuranosyladenine in cellular and cell-free systems. 21 80

The rational design of antitumor and antiviral agents must ultimately take advantage of biochemical differences between normal host cells and transformed cells. The initial experiments must be performed with subcellular or cellular model systems. For the studies with arabinosyl nucleosides we have chosen those enzyme systems, synthesizing DNA and RNA; being precursor analogues, the different arabinosyl nucleosides have been added in the triphosphate state to the different DNA- and RNA polymerase assays. 1-beta-D-Arabinofuranosylcytosine-5'-triphosphate has been found to inhibit the RNA-dependent DNA polymerases (isolated from oncogenic RNA viruses) 200-fold more sensitively than viral and cellular DNA-dependent DNA polymerases. Recent results, showing that RNA-leukemia-virus-related sequences are present in DNA of some human leukemia patients might support the assumption that the efficacy of this antimetabolite in the treatment of acute leukemia is due to its, at least relative selective inhibitory activity on reverse transcriptase. 9-beta-D-Arabinofuranosyladenine-5'-triphosphate is a strong inhibitor of cellular DNA polymerases with the cytological consequence of an inhibition of cell proliferation. The clinical benefit of the compound in treatment of tumors is dependent on their levels of adenosine deaminase. The triphosphate of this compound is a 100-fold more sensitive inhibitor of the herpesvirus DNA polymerase compared to the cellular replicative DNA polymerase. In addition the analogue, incorporated into herpesvirus DNA, acts as chain terminator. These effects are the biochemical basis for the highly selective antiherpesvirus activity of this antimetabolite. The anomer 9-alpha-D-arabinofuranosyladenine-5'-triphosphate only inhibits cellular replicative DNA polymerase and has no effect on herpesvirus DNA polymerase. Consequently this agent acts only cytostatically and not antivirally. Concerning 1-beta-D-arabinofuranosyluracil and 1-beta-D-arabinofuranosylthymine no pronounced antitumor or antiviral effect is known.
 ...
PMID:Rational design of arabinosyl nucleosides as antitumor and antiviral agents. 61 2

Forty-nine children with recurrent acute lymphoblastic leukemia (ALL) were entered into a randomized Phase II trial evaluating 2'-deoxycoformycin (dCF) alone or in combination with adenine arabinoside (ara-A). 2'-Deoxycoformycin is an inhibitor of adenosine deaminase (ADA), an enzyme found in relatively high amounts in malignant lymphoid cells. Ara-A inhibits DNA polymerase and DNA synthesis. Because its efficacy in vivo as an anticancer agent is limited by its rapid inactivation by ADA, ara-A was combined with dCF to produce cytoreductive levels of ara-A. Twenty-four patients were assigned to receive dCF alone and 25 to receive the combination. No patient responded to dCF alone, and one patient developed a complete remission after treatment with the combination. The toxicity of dCF alone was minimal, except for one patient who became obtunded on day 5 following the first cycle of therapy. In contrast, five patients developed severe toxicity with the combination, including renal failure (three patients), hepatic failure (three patients), and neurologic toxicity (two patients). These results indicate that, at the doses and schedule used in this study, the combination of dCF and ara-A has significant toxicity and minimal activity against recurrent ALL in children.
 ...
PMID:Lack of significant activity of 2'-deoxycoformycin alone or in combination with adenine arabinoside in relapsed childhood acute lymphoblastic leukemia. A randomized phase II trial from the Childrens Cancer Study Group. 144 10

The mode of action of antiviral agents (interferon and adenine arabinoside) was studied in human and in animals chronically infected with hepadna virus. Interferon (36-100 megaunits) was given to 20 carrier patients, and hepatitis B virus (HBV)-DNA replicative forms were studied in pre- and post-treatment biopsies. ARA-A was given intravenously to duck hepatitis B virus (DHBV)-infected ducks. Changes in intrahepatic viral replicative forms were studied by Southern blotting using 32P-labelled HBV or DHBV probe. Our study indicates that both interferon and ARA-A seem to effectively decrease 'mature' forms of viral DNA by an effect on either mRNA or DNA polymerase. However, the supercoiled viral DNA tends to resist the treatment, and may become the transcribing template for a new cycle of viral replication after cessation of the drugs.
 ...
PMID:In vivo study of the mechanism of action of antiviral agents against hepadna virus replication in the liver. Resistance of supercoiled viral DNA. 243 76

9-beta-D-Arabinofuranosyladenine (ara-A) is an inhibitor of DNA replication with antitumor and antiviral activity. The molecular basis for this inhibitory effect has remained unclear. The present work has examined the effects of 9-beta-D-arabinofuranosyladenine-triphosphate on DNA polymerase-beta. These studies were performed on different M13 phage DNA templates. The findings demonstrate that 9-beta-D-arabinofuranosyladenine is incorporated into the elongating DNA strand by DNA polymerase-beta. The findings also demonstrate that the incorporated 9-beta-D-arabinofuranosyladenine residue acts as a relative chain terminator. Furthermore, the relative chain-terminating effects of this agent are sequence specific and reversed by competition with deoxyadenosine-triphosphate for incorporation into the DNA strand. These findings are in concert with hydrogen bonding differences of the incorporated arabinosyl moiety which alters reactivity of the chain terminus and thereby inhibits elongation. These findings are also in agreement with recent studies of 1-beta-D-arabinofuranosylcytosine and provide insights into the sequence specific effects of these agents.
 ...
PMID:Sequence-specific inhibition of DNA strand elongation by incorporation of 9-beta-D-arabinofuranosyladenine. 246 40

Sensitivity of Herpes Simplex Virus type I (HSV-I) mutants carrying genetic defect in the DNA polymerase and thymidine kinase genes to the action of some drugs was studied. TK- mutant of HSV-I was resistant to Ara-T and ACG and sensitive to PAA, Ara-A as well as to ribavirin and ADEA. PAAr mutant of HSV-I was resistant to PAA, Ara-A, ACG and sensitive to Ara-T, ribavirin and ADEA. A double mutant of HSV-I-TK-, PAAr was resistant to all drugs, except for ribavirin and ADEA. To inhibit reproduction of HSV with genetic defect, it is important using drugs of independent mode of action on the function of defective viral gene.
 ...
PMID:[Inhibition of the reproduction of a herpes simplex I virus carrying mutations in the thymidine kinase and DNA polymerase genes]. 301 23

Varicella zoster was isolated from the vitreous of a patient with the acute retinal necrosis (ARN) syndrome. We utilized a plaque reduction assay to determine the in vitro susceptibility of the ARN isolate to 6 antiviral drugs. The effective doses for 50% inhibition of plaque numbers were 5.3 microM for for acyclovir, 4.7 microM for DHPG, 8.7 microM for ARA-A, 100.7 microM for phosphonoacetic acid, 0.07 microM for BVdU and 2.4 microM for IUdR. Similar inhibitory values were obtained for the OKA vaccine strain of varicella zoster virus. These data do not support the notion that the ARN strain may represent a mutant of varicella zoster virus with significant alterations in either the viral thymidase kinase or DNA polymerase genes based upon its antiviral sensitivities. The implications of these results regarding the role of antiviral chemotherapy in the ARN syndrome are discussed.
 ...
PMID:Antiviral sensitivities of the acute retinal necrosis syndrome virus. 303 Jun 44

Adenine arabinoside (Ara-A) therapy and abrupt withdrawal of corticosteroids have both been used in the treatment of chronic infections due to hepatitis B virus (HBV). In order to better understand the effects and mechanism of action of these treatments, we treated ducks chronically infected with duck hepatitis B virus (DHBV) with different dosage regimens of the two therapies. We measured endogenous DNA polymerase activity and used sensitive molecular biological techniques to monitor serum and intrahepatic viral replicative forms during and after drug treatment. Ara-A had a transient, dose related inhibitory effect on DHBV replication. Viral plus strand synthesis was disproportionately affected. Following the cessation of Ara-A treatment markers of viral replication returned to their baseline values. We conclude that Ara-A exerts its effect through inhibition of viral DNA polymerase. Corticosteroid treatment results in an increase in DHBV replication, but steroid withdrawal results in a short-lived transient decrease in markers of viral replication to below pretreatment values. Our results suggest that steroid withdrawal decreases hepadna virus replication through a mechanisms of immune modulation. On the basis of these results and previous trials in HBV infected patients, we predict that neither agent will efficiently eliminate viral replication in chronic hepadna virus infection when used as the sole therapeutic modality. We suggest that the differences in the mechanisms of action of Ara-A treatment and corticosteroid withdrawal be exploited, and the use of combination therapy be explored.
 ...
PMID:Effects of adenine arabinoside and corticosteroid on replication of duck hepatitis B virus DNA in the liver. 375 97

Adenine arabinoside is an antiviral agent which has been used in a number of clinical studies for the treatment of chronic infections with hepatitis B virus. In order to better understand its effects and mode of action, we treated ducks chronically infected with duck hepatitis B virus with a 2-week course and monitored the effects of the drug on viral replication by studying duck hepatitis B virus DNA in liver and serum using molecular biological techniques. We found the drug to be effective in ducks only at much higher doses than those used in humans. At high doses, adenine arabinoside had a dose-related inhibitory effect on viral replication during treatment, but there was a rapid return toward baseline values soon after the cessation of treatment. The supercoiled form of viral DNA was found to be most resistant to adenine arabinoside therapy, and the drug had a disproportionate inhibitory effect on viral plus (noncoding) strand synthesis. We conclude that adenine arabinoside likely exerts its effect in hepadna virus infections predominantly through inhibition of viral DNA polymerase. On the basis of our current study and previous trials in hepatitis B virus-infected patients, we predict that adenine arabinoside will not efficiently eliminate viral replication in chronic hepadna virus infection, when used as the sole therapeutic modality. Adenine arabinoside may have a role to play as an adjunct to immunomodulation or interferon therapy in chronic hepatitis B virus infection in man.
 ...
PMID:Effects of adenine arabinoside on serum and intrahepatic replicative forms of duck hepatitis B virus in chronic infection. 380 2

The efficacy of adenine arabinoside (Ara-A) alone or in combination with prednisolone utilizing its withdrawal effect was studied in 43 patients with deoxyribonucleic acid polymerase- and hepatitis B e antigen-positive chronic hepatitis. Ten patients were treated with 10 mg/kg body wt of Ara-A alone for 4-8 wk. In 9 cases, prednisolone (40 mg/day) was given at a constant dosage for 4 wk before Ara-A treatment. Fourteen patients received oral prednisolone alone for 4 wk, and 10 patients served as untreated controls. Six of 9 patients (67%) undergoing the combination therapy became seronegative for hepatitis B e antigen, whereas only 4 of 24 patients (17%) treated either with Ara-A alone or prednisolone alone lost the antigen. Two of the 10 untreated patients became seronegative for hepatitis B e antigen during the same follow-up period of 9 mo. This prospective controlled study suggests that the combination of immunomodulation by steroid withdrawal and subsequent Ara-A is more effective in the treatment of patients with chronic liver disease and active hepatitis B virus replication than treatment with Ara-A alone.
 ...
PMID:Combination of short-term prednisolone and adenine arabinoside in the treatment of chronic hepatitis B. A controlled study. 400 15


1 2 Next >>