| Assay Method Information | |
| | PRMT5:MEP50 FlashPlate Assay without MTA |
| Description: | The assay uses purified human, PRMT5 enzyme to convert S-adenosyl-L-[methyl-3H]methionine plus histone H4 L-arginine to S-adenosyl-L-homocysteine plus histone H4 [methyl-3H]-L-arginine. The assay was carried out using Streptavidin-coated FlashPlates (Perkin Elmer), which contained a scintillant embedded in the plastic of the plate. The histone H4 peptide substrate was conjugated with biotin, which binds to the streptavidin-coated well of the plate, placing the H4 peptide in close proximity to the side well and the scintillant. The transfer of the tritiated methyl group from S-adenosyl-L-[methyl-3H]methionine to the bound histone H4 peptide generated a radiolabeled histone H4, which was quantitated by measuring in a scintillation counter to determine the activity of PRMT5 enzyme in the presence and absence of compound. The assay reactions also were conducted to determine whether the compounds exhibit MTA-cooperative activity. Briefly, compounds of the present invention were solubilized in 100% DMSO at a highest concentration of 10 mM. For IC50 determinations, the initial starting concentration for the serial dilutions of each compound was 50 μM. Control samples lacking compound, PRMT5/MEP50 complex or various reaction components also were prepared and processed in parallel with compound test samples. SAH was used as a positive control for assay validation. To measure PRMT5 inhibitory activity, 3 nM PRMT5/MEP50 complex (Reaction Biology Corporation) was preincubated with test compound in assay buffer containing 40 nM histone H4 peptide (amino acids 1-15)-Biotin conjugate for 20 min at room temperature. The enzymatic reaction was initiated by adding 1 μM tritiated S-adenosyl methionine (final concentration) and the reaction is allowed to proceed for 20 min. The reaction was stopped and the amount of bound, tritiated H4 peptide in each sample was determined using a scintillation counter. The IC50 value for each compound was calculated from each 10-point dose-response curve for samples minus MTA using GraphPad Prism software. |
| Affinity data for this assay | |
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