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)

Vinyl chloride is a known human and rodent carcinogen that forms several cyclic base derivatives in DNA. The mutagenic potential of these derivatives has been examined in vitro but not in vivo. One of these derivatives, N2,3-ethenoguanine (epsilon G), is known to base pair with both cytosine and thymine during in vitro DNA synthesis, which would result in G----A transitions. To determine the base pairing specificity of this labile guanine derivative in Escherichia coli, we have developed a genetic reversion assay for guanine derivatives. The assay utilizes DNA polymerase-mediated analogue insertion into a bacteriophage vector, M13G*1, which detects all single-base substitutions at position 141 of the lacZ alpha gene by change in plaque color. After the insertion of a single epsilon G opposite the template cytosine at position 141 by use of epsilon dGTP and DNA polymerase and further extension with all four normal dNTPs, the DNA was transfected into E. coli. Transfection of M13G*1 containing epsilon G at the target site yielded 135 mutants among 26,500 plaques, 134 of which represented G----A transitions. The uncorrected mutation frequency was 0.5%, as compared with the control value, approximately 0.02%; when corrected for epsilon G content and penetrance, the calculated mutagenic potential of epsilon G (mutations/analogue) was about 13%. We thus conclude that epsilon G specifically induces G----A transitions during DNA replication in E. coli. The M13G*1 assay may permit the testing of other labile guanine derivatives not otherwise amenable to mutagenesis studies.
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PMID:The vinyl chloride DNA derivative N2,3-ethenoguanine produces G----A transitions in Escherichia coli. 194 66

A series of herpes simplex virus isolates were recovered from a bone marrow transplant patient who received prolonged acyclovir therapy for indolent herpes simplex mouth and throat ulceration. Of 14 isolates received 10 were resistant to acyclovir and partially resistant to phosphonoacetic acid. Biochemical characterization revealed that resistance was due to an alteration in the virus DNA polymerase. DNA sequence analysis of the polymerase gene of a plaque-purified resistant virus isolate revealed a single nucleotide change when compared with the sequence of the gene of a plaque-purified sensitive isolate. This single base change resulted in a predicted amino acid substitution of Gly to Ser at residue number 841, a putative functional region of the polymerase.
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PMID:Characterization of a DNA polymerase mutant of herpes simplex virus from a severely immunocompromised patient receiving acyclovir. 254 43

A series of clinical isolates of herpes simplex virus type 2 were taken from a patient with chronic lymphocytic leukemia. Acyclovir (ACV) susceptibility assays revealed that some isolates were resistant to ACV and cross-resistant to ganciclovir but not to phosphonoacetic acid. The nature of the resistance was examined further. A number of cloned variants were generated, and thymidine kinase and DNA polymerase assays were carried out. Variants that were resistant to ACV were found to be thymidine kinase deficient. Evidence for alteration in the DNA polymerase was not found when ACV triphosphate or phosphonoacetic acid was used as the inhibitor. In vivo studies with the plaque-purified viruses showed that ACV resistance was associated with a reduced neurovirulence. In a zosteriform model, virus resistant to ACV was unable to induce secondary spread in the same dermatome, to invade the peripheral nervous system or the central nervous system, or to establish latent infections.
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PMID:Biological and biochemical characterization of clinical isolates of herpes simplex virus type 2 resistant to acyclovir. 254 86

Clinically acquired acyclovir resistance in herpes simplex has usually been associated with a deficiency in viral thymidine kinase, which, in turn, has been linked with attenuated virulence in animal models. Diminished pathogenicity in thymidine kinase-deficient isolates has been partly responsible for controversies about the clinical significance of antiviral resistance. We report on a series of resistant virus isolates from a patient who had severe, progressive esophagitis. These isolates had various thymidine kinase activities, ranging from 2.8% to 130% when compared with the activity of the isolate obtained before treatment; the resistant isolate 615 retained enzyme activity as well as neurovirulence in an encephalitis model. Plaque purification showed a heterogeneous mixture containing at least one acyclovir-resistant, foscarnet-resistant plaque isolate (615.8) fully able to phosphorylate acyclovir. The 3.3-kbp BamHI fragment containing most of the DNA polymerase gene from isolate 615.8 was purified and used to successfully transfer both acyclovir and foscarnet resistance. Acquisition of in-vitro acyclovir resistance was associated with progression of clinical disease, as well as with maintenance of pathogenicity in an animal model and at least one mutation in viral DNA polymerase. Patients with herpes simplex infections that progress during acyclovir therapy should be observed for acquisition of resistance in the setting of antiviral chemotherapy; future studies should also consider the presence of heterogeneous virus populations in such patients.
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PMID:Progressive esophagitis from acyclovir-resistant herpes simplex. Clinical roles for DNA polymerase mutants and viral heterogeneity? 255 68

(R,S)-9-(3-hydroxy-2-phosphonomethoxypropyl)guanine [(R,S)-HPMPG] exhibits broad spectrum antiviral activity with an ED50 of less than 1 microM against herpes simplex virus (HSV) types 1 and 2, varicella zoster virus, human cytomegalovirus (HCMV) and vaccinia in plaque reduction assays. Wild type HSV-2 and its thymidine kinase deficient variant are equally sensitive to (R,S)-HPMPG. (R,S)-HPMPG is 100-fold more potent than acyclovir (ED50 = 0.45 microM vs. 44 microM, respectively) against HCMV in cell culture, and 10-fold more active than acyclovir in extending survival time in mice intraperitoneally infected with 70 LD50 HSV-1. However, (R,S)-HPMPG is toxic when administered repeatedly at 44 mg/kg/day in uninfected adult mice. The diphosphoryl derivative of HPMPG was enzymatically synthesized and is a competitive inhibitor of HSV-1 DNA polymerase relative to dGTP (K1 = 0.03 microM). HPMPG-PP is 70-fold less active at inhibiting HeLa DNA polymerase alpha than HSV-1 DNA polymerase. At concentrations between 0.3 and 1.5 microM (R,S)-HPMPG inhibited HSV-1 DNA replication greater than or equal to 50% in infected cells as measured by nucleic acid hybridization. Consistent with inhibition of viral DNA synthesis, 6 to 30 microM (R,S)-HPMPG reduces late viral polypeptide synthesis in HSV-1 infected cells. These data indicate that (R,S)-HPMPG is a thymidine kinase independent broad spectrum antiviral drug which is capable of inhibiting viral DNA polymerase.
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PMID:Broad-spectrum antiviral activity of the acyclic guanosine phosphonate (R,S)-HPMPG. 285 86

The activities of the purine acyclic nucleoside 9-(1,3-dihydroxy-2-propoxymethyl)guanine (DHPG) against two human and five animal strains of cytomegalovirus were compared with those of acyclovir. DHPG was significantly more active than acyclovir against all but one (mouse cytomegalovirus) of the strains tested, with 50% effective doses ranging from 5 to 13 microM, as determined by plaque reduction assays in human embryonic lung (MRC-5) and human embryonic tonsil cells. Both DHPG and acyclovir inhibited virus replication at concentrations considerably lower than those necessary to inhibit cell proliferation. In mode-of-action studies, the triphosphates of DHPG and acyclovir inhibited human cytomegalovirus DNA polymerase. DHPG phosphorylation to the active triphosphate was enhanced in infected cells; however, this enzymatic activity was unrelated to thymidine kinase. In animal studies, DHPG was slightly more effective than acyclovir in reducing mouse cytomegalovirus-induced mortality.
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PMID:Activity of 9-(1,3-dihydroxy-2-propoxymethyl)guanine compared with that of acyclovir against human, monkey, and rodent cytomegaloviruses. 301 Aug 40

The anti-cytomegalovirus activities of four phosphate derivatives of 9-(1,3-dihydroxy-2-propoxymethyl)guanine (DHPG) were evaluated against human, monkey and murine viruses. The 5'-mono-, 3'5'-bis(mono-), and 3',5'-cyclic monophosphate and 5'-homophosphonate forms of DHPG inhibited virus plaque formation at 1-15 microM. The cyclic phosphate and homophosphonate were more active than the other compounds against murine cytomegalovirus (MCMV) in vitro. In an in vivo MCMV infection model, DHPG homophosphonate and DHPG were equally effective at reducing mortality at greater than or equal to 10 mg/kg. The cyclic phosphate was active at 10-20 mg/kg but toxic at greater than or equal to 40 mg/kg. The phosphorylation of DHPG phosphate and DHPG phosphonate, as well as the inhibition of human cytomegalovirus DNA polymerase by their respective triphosphates, were also examined.
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PMID:In vitro and in vivo activities of phosphate derivatives of 9-(1,3-dihydroxy-2-propoxymethyl)-guanine against cytomegaloviruses. 302 Oct 55

Induction of acyclovir resistance was studied in the immune compromised host by multiple passage of plaque-purified herpes simplex type I strains in athymic nude mice receiving suboptimal antiviral therapy. Mice infected with a highly pathogenic clinical isolate rapidly developed infections that were resistant to therapy. Viruses isolated from these mice had decreased in-vitro sensitivities to acyclovir, as well as altered characteristics when assayed by [125I]plaque autoradiography. In contrast, less virulent laboratory strains, or a genetically stable clinical isolate, showed no indication of mutation to resistance after extended passage in this mouse model. Highly pathogenic viruses may increase the probability of mutation to resistance because of the large amount of infectious virus they produce, while viruses of equivalent virulence may produce different amounts of drug-resistant progeny because of alterations in the replication fidelity of the viral DNA polymerase.
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PMID:Induction of acyclovir-resistant mutants of herpes simplex virus type I in athymic nude mice. 302 59

Replication of equine herpesvirus type 1 (EHV-1) was sensitive to 9-(1,3-dihydroxy-2-propoxymethyl)guanine(DHPG) but relatively resistant to E-5-(2-bromovinyl)-2'-deoxyuridine (BVDU). Likewise, plaque formation by EHV-1 was inhibited by DHPG, but not by BVDU. Plaque formation by a thymidine kinase-negative (tk-) mutant of EHV-1 was not inhibited by DHPG. In order to investigate biochemical mechanisms determining the differential sensitivity of EHV-1 to these drugs, the EHV-1-encoded thymidine kinase enzyme activity (TK)1 was partially purified from EHV-1-infected cells and analyzed. The EHV-1-induced enzyme utilized both ATP and CTP as phosphate donors and differed in relative electrophoretic mobility from the TKs of mock-infected and HSV-1-infected cells. Phosphorylation of 3H-dThd by the EHV-1 TK was inhibited by AraT, IdUrd, BVDU, and DHPG. The EHV-1 TK phosphorylated 125I-dCyd and 3H-ACV. The results indicate that EHV-1 encodes a pyrimidine deoxyribonucleoside kinase with broad nucleoside substrate specificity. These observations suggest that the failure of BVDU to inhibit EHV-1 replication is not attributable to an inability of the EHV-1 TK to phosphorylate BVDU, but may result from the incapacity of the viral TK to convert BVDU monophosphate to the triphosphate or from lack of inhibitory effect of BVDU triphosphate on viral DNA polymerase reactions.
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PMID:Phosphorylation of nucleoside analogs by equine herpesvirus type 1 pyrimidine deoxyribonucleoside kinase. 302 47

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.
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PMID:Antiviral sensitivities of the acute retinal necrosis syndrome virus. 303 Jun 44


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