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Assay Method Information

Assay Name:  Ubitquin-Rhodamine 110 Assay for USP1 Activity
Description:  The HTS assay was performed in a final volume of 20 μL in assay buffer containing 20 mM Tris-HCl (pH 8.0, (1M Tris-HCl, pH 8.0 solution; Corning 46-031-CM)), 2 mM CaCl2 (1M Calcium Chloride solution; Sigma #21114) 1 mM GSH (L-Glutathione reduced; Sigma #G4251), 0.01% Prionex (0.22 M filtered, Sigma #G-0411), and 0.01% Triton X-100. Stock compound solutions were stored at −20° C. as 10 mM in DMSO. Up to 1 month prior to the assay, 2 mM test compounds were pre-dispensed into assay plates (Black, low volume; Corning #3820) and frozen at −20° C. Prestamped assay plates were allowed to come to room temperature on the day of the assay. For the screen, 100 nL of 2 mM was pre-dispensed for a final screening concentration of 10 M (DMSO(fc)=0.5%). The final concentration of the enzyme (USP1, construct USP1 (I-785, GG670, 671AA)/UAF1 (I-677)-Flag; Viva) in the assay was 100 pM. Final substrate (Ub-Rh110; Ubiquitin-Rhodamine 110, R&D Systems #U-555) concentration was 25 nM with [Ub-Rh110]<<Km. 10 μL of 2× enzyme was added to assay plates (pre-stamped with compound) either simultaneously with 2×Ub-Rh110 or preincubated with USP1 40 minutes prior to the addition of 10 μL of 2×Ub-Rh110 to compound plates. Plates were incubated stacked for 45 minutes at room temperature before fluorescence was read on the Envision (Excitation at 485 nm and Emission at 535 nm; Perkin Elmer) or on the PheraSTAR (Excitation at 485 nm and Emission at 535 nm; BMG Labtech)For follow-up IC50 studies, each assay was performed in a final volume of 15 μL in assay buffer containing 20 mM Tris-HCl (pH 8.0, (1M Tris-HCl, pH 8.0 solution; Corning 46-031-CM)), 1 mM GSH (L-Glutathione reduced; Sigma #G4251), 0.03% BGG (0.22 M filtered, Sigma, #G7516-25G), and 0.01% Triton X-100 (Sigma, #T9284-10L). Nanoliter quantities of either an 8-point or 10-point, 3-fold serial dilution in DMSO was pre-dispensed into assay plates (Perkin Elmer, ProxiPlate-384 F Plus, #6008269) for a final test concentration range of either 25 μM to 11 nM or 25 μM to 1.3 nM, respectively. The final concentration of the enzyme (USP1, construct USP1 (I-785, GG670, 671AA)/UAF1 (I-677)-Flag; Viva) in the assay was 25 pM. Final substrate (Ub-Rh110; Ubiquitin-Rhodamine 110, R&D Systems #U-555) concentration was 25 nM with [Ub-Rh110]<<Km. 5 μL of 2× enzyme was added to assay plates (pre-stamped with compound) preincubated with USP1 for 30 minutes and then 5 μL of 2×Ub-Rh110 was added to assay plates. Plates were incubated stacked for 20 minutes at room temperature before 5 μL of stop solution (final concentration of 10 mM citric acid in assay buffer (Sigma, #251275-500G)). Fluorescence was read on the Envision (Excitation at 485 nm and Emission at 535 nm; Perkin Elmer) or on the PheraSTAR (Excitation at 485 nm and Emission at 535 nm; BMG Labtech).
Affinity data for this assay
 

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Last update November 1, 2007
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