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Assay Method Information

Assay Name:  Wild-Type PRC2 Enzyme Assay
Description:  eneral Procedure for Wild-Type PRC2 Enzyme Assay on Oligonucleosome Substrate. The assays was performed in a buffer consisting of 20 mM bicine (pH=7.6), 0.5 mM DTT, 0.005% BSG, 100 mM KCl and 0.002% Tween20, prepared on the day of use. Compounds in 100% DMSO (1 μL) were spotted into polypropylene 384-well V-bottom plates (Greiner) using a Platemate 23 outfitted with a 384-channel pipet head (Thermo). DMSO (1 μL) was added to columns 11, 12, 23, 24, rows A-H for the maximum signal control, and SAH, a known product and inhibitor of PRC2 (1 μL) was added to columns 11, 12, 23, 24, rows I-P for the minimum signal control. A cocktail (40 μL) containing the wild-type PRC2 enzyme and chicken erythrocyte oligonucleosome was added by Multidrop Combi (Thermo). The compounds were allowed to incubate with PRC2 for 30 min at 25 C., then a cocktail (10 μL) containing a mixture of non-radioactive and 3H-SAM was added to initiate the reaction (final volume=51 μL). The final concentrations were as follows: wild-type PRC2 enzyme was 4 nM, non-radioactive SAM was 430 nM, 3H-SAM was 120 nM, chicken erythrocyte olignonucleosome was 120 nM, SAH in the minimum signal control wells was 1 mM and the DMSO concentration was 1%. The assay was stopped by the addition of non-radioactive SAM (10 μL) to a final concentration of 600 μM, which dilutes the 3H-SAM to a level where its incorporation into the chicken erythrocyte olignonucleosome substrate is no longer detectable. 50 μL of the reaction in the 384-well polypropylene plate was then transferred to a 384-well Flashplate and the chicken erythrocyte nucleosomes were immobilized to the surface of the plate, which was then washed three times with 0.1% Tween20 in a Biotek ELx405 plate washer. The plates were then read in a PerkinElmer TopCount platereader to measure the quantity of 3H-labeled chicken erythrocyte oligonucleosome bound to the Flashplate surface, measured as disintegrations per minute (dpm) or alternatively, referred to as counts per minute (cpm).% Inhibition Calculation% ⁢ ⁢ inh = 100 - ( dpm cmpd - dpm min dpm max - dpm min ) 100Where dpm=disintegrations per minute, cmpd=signal in assay well, and min and max are the respective minimum and maximum signal controls.Four-Parameter IC50 FitY = Bottom + ( Top - Bottom ) 1 + ( X IC 50 ) Hill ⁢ ⁢ CoefficientWhere top and bottom are the normally allowed to float, but may be fixed at 100 or 0 respectively in a 3-parameter fit. The Hill Coefficient normally allowed to float but may also be fixed at 1 in a 3-parameter fit. Y is the % inhibition and X is the compound concentration.
Affinity data for this assay
 

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Last update November 1, 2007
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