Assay Method Information

Assay Name:  Inhibition Assay
Description:  The enzyme activity of NS5B570-Con1 (Delta-21) was measured as an incorporation of tritiated NMP into acid-insoluble RNA products. The complementary IRES (cIRES) RNA sequence was used as a template, corresponding to 377 nucleotides from the 3′-end of HCV (−) strand RNA of the Con-1 strain, with a base content of 21% Ade, 23% Ura, 28% Cyt, and 28% Gua. The cIRES RNA was transcribed in vitro using a T7 transcription kit (Ambion, Inc.) and purified using the Qiagen RNeasy maxi kit. HCV polymerase reactions contained 50 nM NS5B570-Con1, 50 nM cIRES RNA, about 0.5 μLCi tritiated NTP, 1 μM of competing cold NTP, 20 mM NaCl, 40 mM Tris-HCl (pH 8.0), 4 mM dithiothreitol, and 4 mM MgCl2. Standard reactions were incubated for 2 h at 37° C., in the presence of increasing concentration of inhibitor. At the end of the reaction, RNA was precipitated with 10% TCA, and acid-insoluble RNA products were filtered on a size exclusion 96-well plate. After washing of the plate, scintillation liquid was added and radio labeled RNA products were detected according to standard procedures with a Trilux Topcount scintillation counter. The compound concentration at which the enzyme-catalyzed rate was reduced by 50% (IC50) was calculated by fitting the data to a non-linear regression (sigmoidal).
Affinity data for this assay
 

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