• Environmental Mutagens and Carcinogens
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• v.10 no.2
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• pp.85-92
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• 1990

The effects of aphidicolin (APC), 2`,3`-dideoxythymidine 5`-triphosphate (ddTTP), and novobiocin (NOV) on the frequencies of chromosome aberrations induced by ethyl methanesulfonate (EMS) or bleomycin (BLM) were examined in synchronized Chinese hamster ovary (CHO)-K$_1$ cells. The cells were synchronized by the thymidine double block method. APC, ddTTP and NOV alone did not affect the frequencies of chromosome aberrations. The cells in late G$_1$ and early S phases were sensitive to the induction of chromosome aberrations by EMS, wherase cells in G$_2$ phase were most sensitive to chromosme aberration by BLM.

• Journal of Microbiology and Biotechnology
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• v.14 no.5
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• pp.1022-1030
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• 2004

The gene encoding Aquifex pyrophilus (Apy) DNA polymerase was cloned and sequenced. The Apy DNA polymerase gene consists of 1,725 bp coding for a protein with 574 amino acid residues. The deduced amino acid sequence of Apy DNA. polymerase showed a high sequence homology to Escherichia coli DNA polymerase I-like DNA polymerases. It was deduced by amino acid sequence alignment that Apy DNA polymerase, like the Klenow fragment, has only the two domains, the $3'{\rightarrow}5'$ exonuclease domain and the $5'{\rightarrow}3'$ polymerase domain, containing the characteristic motifs. The Apy DNA polymerase gene was expressed under the control of T7lac promoter on the expression vector pET-22b(+) in E. coli. The expressed enzyme was purified by heat treatment, and Cibacron blue 3GA and $UNO^{TM}$ Q column chromatographies. The optimum pH of the purified enzyme was 7.5, and the optimal concentrations of KCl and $Mg^{2+}$ were 20 mM and 3 mM, respectively. Apy DNA polymerase contained a double strand-dependent $3'{\rightarrow}5'$ proofreading exonuclease activity, but lacked any detectable $5'{\rightarrow}3'$ exonuclease activity, which is consistent with its amino acid sequence. The somewhat lower thermostability of Apy DNA polymerase than the growth temperature of A. pyrophilus was analyzed by the comparison of amino acid composition and pressure effect.

• Environmental Mutagens and Carcinogens
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• v.9 no.1
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• pp.23-32
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• 1989

Chinese hamster ovary (CHO)-K1 cells echibited a differential sensitivity in the process of DNA repair synthesis induced by ethyl methanesulfonate (EMS) or bleomycin (BLM) in relation to cell cycle. Two assays were employed in this study: alkaline elution and unscheduled DNA synthesis. The post-treat-ment with aphidicolin (APC), an inhibitor of DNA polymerase alpha, inhibited DNA repair synthesis induced by EMS in G2 phase, while APC did not show any effect on BLM-induced DNA repair synthesis in all phases. On the other hands, the 2', 3'-dideoxythymidine (ddTTP), an inhibitor of DNA polymerase beta, inhibited DNA repair synthesis induced by EMS or BLM in both of G1 and G2 phases. These results suggested that the involvement of DNA polymerase alpha and beta in DNA repair was dependent on cell stage or used chemical agent.

• BMB Reports
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• v.35 no.3
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• pp.320-329
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• 2002

A gene, coined tay, for a thermostable DNA polymerase from the novel, extremely thermophilic bacterium Thermoanaerobacter yonseiensis was cloned and expressed in E. coli. Using a DNA polymerase homologous PCR product as a hybridization probe, tay was isolated and sequenced to consist of 2621 nucleotides that encode 872 amino acids. A database analysis showed that DNA polymerase, coined Tay, from T. yonseiensis shared a 39% to 47% identity in the amino acid sequence with those from other DNA polymerases. Tay was overexpressed in E. coli as a fusion protein with a poly-histidine tag at the C-terminus. It was purified by heat treatment, followed by a $Ni^{2+}$-chelate column. The molecular weight of purified Tay was approximately 97 kDa, as shown by SDS PAGE, and it showed high DNA polymerase activity and thermostability. However, it had no 3'$\rightarrow$5' exonuclease activity.

• Annals of Clinical Neurophysiology
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• v.19 no.1
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• pp.40-45
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• 2017

Background: Telbivudine is a nucleoside analogue used for the treatment of chronic hepatitis B, but it often develops mitochondrial toxicity leading to symptomatic myopathy. In this study, three patients with telbivudine induced myopathy were enrolled in order to investigate the nature and pathogenesis of mitochondrial toxicity caused by long-term use of telbivudine. Methods: Clinical features, laboratory findings, muscle pathology, and quantitation of mitochondrial DNA were studied in three patients. Results: Patients presented with progressive muscle weakness with high serum creatine kinase levels. Light microscopic findings of muscle pathology showed ragged red fibers that reacted strongly with succinate dehydrogenase stain, but negative for cytochrome c oxidase activities. Electron microscopy revealed abnormal mitochondrial accumulation with rod shaped inclusions. The quantitative peroxidase chain reaction showed a depletion of mitochondrial DNA in skeletal muscle of the patients. Conclusions: Nucleoside analogues including telbivudine are potent inhibitors of viral DNA polymerases. However, they are not specific for viral DNA and can disturb mitochondrial replication at the same time. All nucleotide analogues should be used with close clinical observation in order to avoid development of mitochondrial myopathy.

• Journal of Microbiology and Biotechnology
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• v.3 no.4
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• pp.224-231
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• 1993

The nucleotide sequence of the xylanase gene (xynY) from alkalophilic Bacillus sp. YC-335 was determined and analyzed. An open reading frame of 1, 062 base pairs for xynY gene was observed and encoded for a protein of 354 amino acids with a molecular weight of 38, 915. S1 nuclease mapping showed that the transcription initiation sites of the xynY gene were different in Bacillus sp. YC-335 and Escherichia coli HB101 (pYS55). S1 mapping also showed that -10 region of the xynY gene recognized by RNA polymerases of E. coli and Bacillus sp. YC-335 were TACAGT and TATGAT , respectively. A ribosome binding site sequence with the free energy of -17.0 Kcal/mol was observed 9 base pairs upstream from the unusual initiation codon, TTG. The proposed signal sequence consisted of 27 amino acids, 2 of which were basic amino acid residues and 21 were hydrophobic amino acid residues. When the amino acid sequences of xylanases were compared, Bacillus sp. YC-335 xylanase showed more than 50% homology with xylanases from B. pumilus, B. subtilis, and B. circulans.

• The Plant Pathology Journal
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• v.30 no.2
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• pp.151-158
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• 2014

Three double-stranded RNAs (dsRNAs), approximately 1.85, 1.65 and 1.27 kb in size, were detected in an isolate of Cytospora sacchari from Iran. Partial nucleotide sequence revealed a 1,284 bp segment containing one ORF that potentially encodes a 405 aa protein. This protein contains conserved motifs related to RNA dependent RNA polymerases (RdRp) that showed similarity to RdRps of partitiviruses. The results indicate that these dsRNAs represent a novel Partitivirus that we tentatively designate Cytospora sacchari partitivirus (CsPV). Treatment of the fungal strain by cyclohexamide and also hyphal tip culture had no effect on removing the putative virus. Phylogenetic analysis of putative RdRp of CsPV and other partitiviruses places CsPV as a member of the genus Partitivirus in the family Partitiviridae, and clustering with Aspergillus ochraceous virus 1.

• Microbiology and Biotechnology Letters
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• v.31 no.1
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• pp.1-12
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• 2003

Myxobacteria are soil bacteria that move by gliding and have a complicated life cycle. In the research over the 25 years the myxobacteria have been shown to be a rich source of potentially useful bioactive substances. So far about 80 different basic compounds and 450 structural variants have been characterized. It is remarkable that myxobacteria produce the substance has special mechanisms. 26 new electron transport inhibitors,5 inhibitors of nucleic acid polymerases, 10 substances that act on the cytoskeleton, and 1 inhibitor of fungal acetyl-CoA carboxylase have been found. Presently, large-scale technical process was not fully established. But one of the compounds from myxobacteria is able to pass the many thresholds, which are on the road to application.

• Journal of Microbiology and Biotechnology
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• v.27 no.7
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• pp.1324-1330
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• 2017

Complete genome sequences of three new plant RNA viruses, Spinach deltapartitivirus 1 (SpDPV1), Spinach amalgavirus 1 (SpAV1), and Spinach latent virus (SpLV), were identified from a spinach (Spinacia oleracea) transcriptome dataset. The RNA-dependent RNA polymerases (RdRps) of SpDPV1, SpAV1, and SpLV showed 72%, 53%, and 93% amino acid sequence identities with the homologous RdRp of the most closely related virus, respectively, suggesting that SpDPV1 and SpAV1 were novel viruses. Sequence similarity and phylogenetic analyses revealed that SpDPV1 belonged to the genus Deltapartitivirus of the family Partitiviridae, SpAV1 to the genus Amalgavirus of the family Amalgaviridae, and SpLV to the genus Ilarvirus of the family Bromoviridae. Based on the demarcation criteria, SpDPV1 and SpAV1 are considered as novel species of the genera Deltapartitivirus and Amalgavirus, respectively. This is the first report of these two viruses from spinach.

• BMB Reports
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• v.37 no.2
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• pp.167-176
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• 2004

Although efficient antiviral lamivudine is used for HBV-infected patients, a prolonged treatment with nucleoside analogs often results in lamivudine-resistant variants. In this study, we evaluated the fidelity of the lamivudine-resistant variants. The FLAG-tagged wild-type (FPolE) and Met550 variants (FPolE/M550A, M550V, and M550I) of HBV DNA polymerases were expressed in insect cells then purified. Like many other reverse transcriptases, no $3'{\rightarrow}5'$ exonuclease activity was detected in the HBV DNA polymerase. Since there is no proofreading activity, then the use of the site-specific nucleotide misincorporation method is beneficial. From the $f_{ins}$ value analysis, it is evident that M550I and M550V exhibit higher fidelity values than the wild-type HBV DNA polymerase, while M550A exhibits similar fidelity values. It is therefore suggested that lamivudine resistance comes from the stringency to dNTP binding and the discrimination of dCTP and lamivudine in M550V and M550I.