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)

The metabolism and mode of action of penciclovir [9-(4-hydroxy-3-hydroxymethylbut-1-yl)guanine; BRL 39123] were studied and compared with those of acyclovir. In uninfected MRC-5 cells, low concentrations of the triphosphates of penciclovir and acyclovir were occasionally just detectable, the limit of detection being about 1 pmol/10(6) cells. In contrast, in cells infected with either herpes simplex virus type 2 (HSV-2) or varicella-zoster virus (VZV), penciclovir was phosphorylated quickly to give high concentrations of the triphosphate ester. Following the removal of penciclovir from the culture medium, penciclovir-triphosphate remained trapped within the cells for a long time (half-lives, 20 and 7 h in HSV-2- and VZV-infected cells, respectively). In HSV-2-infected cells, acyclovir was phosphorylated to a lesser extent and the half-life of the triphosphate ester was only 1 h. We were unable to detect any phosphates of acyclovir in VZV-infected cells. (S)-Penciclovir-triphosphate inhibited HSV-1 and HSV-2 DNA polymerase competitively with dGTP, the Ki values being 8.5 and 5.8 microM, respectively, whereas for acyclovir-triphosphate, the Ki value was 0.07 microM for the two enzymes. Both compounds had relatively low levels of activity against the cellular DNA polymerase alpha, with Ki values of 175 and 3.8 microM, respectively. (S)-Penciclovir-triphosphate did inhibit DNA synthesis by HSV-2 DNA polymerase with a defined template-primer, although it was not an obligate chain terminator like acyclovir-triphosphate. These results provide a biochemical rationale for the highly selective and effective inhibition of HSV-2 and VZV DNA synthesis by penciclovir and for the greater activity of penciclovir than that of acyclovir when HSV-2-infected cells were treated for a short time.
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PMID:Mode of antiviral action of penciclovir in MRC-5 cells infected with herpes simplex virus type 1 (HSV-1), HSV-2, and varicella-zoster virus. 133 46

The activity of 9-(4-hydroxy-3-hydroxymethylbut-1-yl)guanine (BRL 39123) against several herpesviruses was compared with that of acyclovir (ACV). In plaque reduction tests with clinical isolates of herpes simplex virus type 1 (HSV-1), herpes simplex virus type 2 (HSV-2), and varicella-zoster virus, mean 50% inhibitory concentrations (IC50S) (n = number tested) for BRL 39123 were 0.4 (n = 17), 1.5 (n = 13), and 3.1 (n = 5) micrograms/ml, respectively. Corresponding IC50S for ACV were 0.2, 0.6, and 3.8 micrograms/ml. Cytomegalovirus was relatively resistant to BRL 39123 (IC50, 51 micrograms/ml), but equid herpesvirus 1, bovid herpesvirus 2, and felid herpesvirus 1 were susceptible (IC50S, 1.6, 1.2, and 0.9 micrograms/ml, respectively). BRL 39123 was inactive against an HSV-1 strain which does not express thymidine kinase activity, but a DNA polymerase mutant selected for resistance to ACV was sensitive to BRL 39123 (IC50, 1.5 micrograms/ml). In contrast to the results from plaque reduction tests, BRL 39123 was more active than ACV against HSV-1 and of equal activity against HSV-2 in virus yield reduction assays in MRC-5 cells. After treatment of HSV-infected cultures for short periods, BRL 39123 was considerably more effective than ACV at reducing virus replication, and furthermore, after removal of extracellular BRL 39123, virus replication remained depressed for long periods, whereas such persistent activity was not observed with ACV. Neither compound significantly affected MRC-5 cell replication at 100 micrograms/ml, but at 300 micrograms/ml BRL 39123 was more inhibitory than ACV.
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PMID:Antiherpesvirus activity of 9-(4-hydroxy-3-hydroxy-methylbut-1-yl)guanine (BRL 39123) in cell culture. 363 45

For many years, dengue viruses were among the most difficult flaviviruses to isolate and to identify, but technical advances in the past 20 years have facilitated this process. Dengue viruses are usually recovered from specimens by the infection of mosquito-cell cultures. The virus may be passaged several times in cell cultures until a sufficient infectivity titer is attained. The viral nucleocapsid consists of capsid protein and an RNA genome. The dengue genome is a single stranded messenger (positive) sense RNA of approximately 11 kb in length. The isolation of dengue genomic RNA from various sources requires precautions to avoid RNases. RNases are released during cell disruption, and their activity must be inhibited as quickly as possible by using guanidinium thiocyanate in the presence of 2-mercaptoethanol. There has recently been a revolution in molecular biology with the development of the powerful reverse transcriptase (RT) and polymerase chain reaction (PCR) technology. Advanced studies on RT technique lead to much further improvement of the reverse transcriptase enzyme by genetic engineering. The Superscript II RNase H- RT (GIBCO BRL, USA) is genetically engineered DNA polymerase that synthesizes a complementary DNA strand from single-stranded RNA. DNA or an RNA-DNA hybrid. This enzyme is produced from a cloned M-MLV RT gene constructed by the introduction of point mutation in the RNase H active center. The selective mutations within the RNase H domain maintain full polymerase activity. This structural modification eliminates degradation of RNA molecules during the first strand cDNA synthesis. The combination of thermostable DNA polymerase with and without proofreading activity (3'-exonuclease activity), improved buffer conditions and thermal cycling profiles overcome the length limitation of PCR. On the basis of these findings, we have developed a long RT-PCR system for preparing large cDNA fragments of dengue 3 virus (H-87) by using the Superscript II RNase H- RT for reverse transcription and a mixture of Taq and Pwo DNA polymerases for PCR. Three large cDNA fragments covered the full genomic RNA from the 5'-end to the 3'-end of dengue-3 virus (H-87; 10,696 bps) could be successfully prepared as the lengths of 2.437 bps, 3,980 bps and 4,337 bps respectively. The ability of our developed long RT-PCR will bring speed and simplicity to genomic mapping and sequencing and facilitate studies in molecular genetics of dengue viruses.
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PMID:A novel method for the preparation of large cDNA fragments from dengue-3 RNA genome by long RT-PCR amplification. 1141 41