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Assay Method Information

Assay Name:  Determination of HIV-1 Reverse Transcriptase Inhibitory Activity
Description:  The heterodimeric nucleic acid substrate used in the HIV-1 RT polymerase reactions was generated by annealing the DNA primer, biotinylated pD500 (Sigma Aldrich, USA, 5′-biotin-ttg aaa tga ctg cgg tac ggc-3′), SEQ ID NO. 1 to the nucleotide RNA template t500 (derived from hepatitis C virus [HCV] sequence, IBA, Germany, 5′-GAG GUU CAG GUG GUU UCC ACC GCA ACA CAA UCC UUC CUG GCG ACC UGC GUC AAC GGC GUG UGU UGG ACC GUU UAC CAU GGU GCU GGC UCA AAG ACC UUA GCC GGC CCA AAG GGG CCA AUC ACC CAG AUG UAC ACU AAU GUG GAC CAG GAC CUC GUC GGC UGG CAG GCG CCC CCC GGG GCG CGU UCC UUG ACA CCA UGC ACC UGU GGC AGC UCA GAC CUU UAC UUG GUC ACG AGA CAU GCU GAC GUC AUU CCG GUG CGC CGG CGG GGC GAC AGU AGG GGG AGC CUG CUC UCC CCC AGG CCU GUC UCC UAC UUG AAG GGC UCU UCG GGU GGU CCA CUG CUC UGC CCU UCG GGG CAC GCU GUG GGC AUC UUC CGG GCU GCC GUA UGC ACC CGG GGG GUU GCG AAG GCG GUG GAC UUU GUG CCC GUA GAG UCC AUG GAA ACU ACU AUG CGG UCU CCG GUC UUC ACG GAC AAC UCA UCC CCC CCG GCC GUA CCG CAG UCA UUU CAA-3′), SEQ ID NO 2.). The HIV-1 RT wild-type enzyme (final concentration of 83 pM) was combined with an inhibitor or dimethyl sulfoxide (DMSO, 10% in the final reaction mixture) in assay buffer (62.5 mM Tris-HCl [pH 7.8], 1.25 mM dithiothreitol, 7.5 mM MgCl2, 100 mM KCl, 0.03% CHAPS, and 125 μM EGTA). The mixture was then preincubated on an orbital shaker for 30 min at room temperature in microtiter plates (Costar 3365, Corning, USA). A polymerization reaction was initiated by the addition of RNA template/pD500 DNA primer hybrid (16.6 nM final of RNA/DNA hybrid) and dNTPs (2 μM dATP, dGTP, dCTP and 66.6 nM Ru-dUTP (Meso Scale Discovery, USA)). Plate was sealed and incubated for 5-10 min at room temperature on an orbital shaker. Plate was then incubated for 90 min at 37° C. and reactions quenched with 60 μl quenching buffer (50 mM EDTA, 0.7% BSA, 0.7% Tween-20, 0.017% sodium azide in PBS). The resulting solution was incubated at room temperature for an additional 5 min and then 50 μL was transferred to pre-blocked Avidin plates (L15AA, Meso Scale Discovery). Each well of Avidin plate was blocked for 1 h at room temperature with 100 μL 5% BSA in PBS. Blocking solution was removed by tapping vigorously on filter paper to remove all excess liquid. Reaction on pre-blocked avidin plate proceeded for 60 min at room temperature and then contents removed by tapping vigorously on filter paper to remove all excess liquid. After washing plate 3 times with 150 μL 1×PBS and blotting dry between cycles, 150 μL 1× Read Buffer T (4× Read Buffer T, Meso Scale Discovery) was added and incubated for 5 min at room temperature before counting on a Sector Imager S6000 (Meso Scale Discovery). Titration curves and IC50 values were calculated using a four parameter logistic fit according to standard procedures. Briefly, % Inhibition=100×((sample raw value)−(mean value of the low control or 0% inhibition))/((mean value of wells representing 100% inhibition)−(mean value of 0% inhibition)). In this assay, low control wells contain DMSO (0% inhibition) and 100% inhibition wells contain 1 μM efavirenz.
Affinity data for this assay
 

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Last update November 1, 2007
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