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Inhibition of Hepatitis C Virus Replication by Arsenic Trioxide. Der-Ren Hwang, 2004.Hepatitis C virus (HCV) is a serious global problem, and present therapeutics are inadequate to cure HCV infection . In the present study, various antiviral assays show that As2O3 at submicromolar concentrations is capable of inhibiting HCV replication . The 50% effective concentration (EC50) of As2O3 required to inhibit HCV replication was 0.35 µM when it was determined by a reporter-based HCV replication assay, and the EC50 was below 0.2 µM when it was determined by quantitative reverse transcription-PCR analysis . As2O3 did not cause cellular toxicity at this concentration, as revealed by an MTS [3-(4,5-dimethylthiozol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt] assay . A combination of As2O3 and alpha interferon exerted synergistic effects against HCV, as revealed by a multiple linear logistic model and isobologram analysis . Furthermore, in an alternative HCV antiviral system that may recapitulate additional steps involved in HCV infection and replication, As2O3 at 0.3 µM totally abolished the HCV signal, whereas alpha interferon at a high dose (5,000 IU/ml) only partially suppressed the HCV signal . The study highlights the indications for use of a novel class of anti-HCV agent . Further elucidation of the exact antiviral mechanism of As2O3 may lead to the development of agents with potent activities against HCV or related viruses . Thymine at —5 Is Crucial for cpc Promoter Activity of Synechocystis sp . Strain PCC 6714. Masahiko Imashimizu, 2003.The levels of transcripts of the cpc operon were highly reduced in a PD-1 mutant of cyanobacterium Synechocystis sp . strain PCC 6714 . This was due to a substitution of C for T that occurred at 5 bp upstream of the transcription initiation site of the cpc operon . Any substitution for T at the -5 position drastically reduced both in vivo and in vitro promoter activity in cyanobacterium Synechococcus sp . strain PCC 7942 but not the in vivo activity in Escherichia coli . This suggests that the requirement of -5T appears to be specific for a cyanobacterial RNA polymerase-promoter combination . Cloning and Sequencing of a Poly(DL-Lactic Acid) Depolymerase Gene from Paenibacillus amylolyticus Strain TB-13 and Its Functional Expression in Escherichia coli. Yukie Akutsu-Shigeno, 2003.The gene encoding a poly(DL-lactic acid) (PLA) depolymerase from Paenibacillus amylolyticus strain TB-13 was cloned and overexpressed in Escherichia coli . The purified recombinant PLA depolymerase, PlaA, exhibited degradation activities toward various biodegradable polyesters, such as poly(butylene succinate), poly(butylene succinate-co-adipate), poly(ethylene succinate), and poly(  -caprolactone), as well as PLA . The monomeric lactic acid was detected as the degradation product of PLA . The substrate specificity toward triglycerides and p-nitrophenyl esters indicated that PlaA is a type of lipase . The gene encoded 201 amino acid residues, including the conserved pentapeptide Ala-His-Ser-Met-Gly, present in the lipases of mesophilic Bacillus species . The identity of the amino acid sequence of PlaA with Bacillus lipases was no more than 45 to 50%, and some of its properties were different from those of these lipases .
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