Assay Method Information

Assay Name:  ATR/ATRIP Enzymatic Assay
Description:  Human full-length FLAG-TEV-ATR and His6-ATRIP were co-expressed in HEK293 cells. The cell pellet (20 g) was harvested and lysed in 100 mL of lysis buffer (20 mM Tris-HCl pH 7.5 at room temperature, 137 mM NaCl, 10% glycerol, 1 mM DTT, 1% (v/v) Tween-20, 0.1% (v/v) NP-40, complete protease inhibitor cocktail tablets, phosphatase inhibitor cocktail tablets, 2 mM MgCl2, 0.2 mM EDTA, and 1 mM ATP). After sonication and centrifugation, the supernatant was incubated at 4° C. for 3 hours with 1 mL of anti-FLAG resin (Sigma catalog # A2220) that had been pre-equilibrated in buffer A (20 mM Tris-HCl pH 7.5 at room temperature, 137 mM NaCl, 10% glycerol, 1 mM DTT, 2 mM MgCl2, and 0.2 mM EDTA). The sample was loaded into a column, and then washed with buffer A three times. Protein was subsequently eluted with 2 ml of buffer B (buffer A+200 m/ml 3×FLAG peptide).The ability of new chemical matter to inhibit the ATR catalytic activity in this ATR/ATRIP complex was assessed using a Caliper-based assay. A 2× enzyme solution (i.e., 4 nM enzyme) was prepared using 1× Kinase Reaction Buffer (25 mM HEPES pH 8, 0.0055% Brij-35, 10 mM MnCl2, and 1 mM DTT). A 2× peptide solution was then prepared consisting of 10 uM FAM-labeled RAD17 peptide (GL Biochem, catalog #524315) in 1× Kinase Reaction Buffer supplemented with 2 μM ATP. 10 μL of the 2× enzyme solution was transferred to an assay plate containing 60 nL of test compound (from a 3× serial dilution) in 100% DMSO. Following a 30 minute incubation at 28° C., 10 μL of the 2× peptide solution was then transferred to the same assay plate. The reaction was allowed to incubate at 28° C. for 6 hours. After adding 30 μL of stop buffer (100 mM HEPES pH 7.5, 0.015% Brij-35, 0.2% Coating-3 Reagent (PerkinElmer, catalog # PN760050), and 50 mM EDTA), data were collected on a Caliper instrument. Conversion values were converted to inhibition values via the following equation: % inhibition=(max−conversion)/(max−min)*100, whereby max corresponds to the DMSO control and min corresponds to the low control. IC50 values were calculated using the following equation in XLFit: Y=Bottom+(Top-Bottom)/1+(IC50/X){circumflex over ( )}HillSlope).
Affinity data for this assay
 

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