External ID: HMS1262

Protocol: NEC is stored at -80 degrees at a concentration of 15mg/ml in single use aliquots.

On the day of the screen, 20ul of purified NEC is aliquoted using a Multidrop Combi reagent dispenser into 384 well plates (Corning 3824). 100nl of compound dissolved in DMSO was transferred to each well of the assay plated via pin transfer. The plates (NEC + compound) are incubated at room temperature for 3 hours. Acceptor and donor reagents (CisBio 620/665 pair) are combined then added to each well at 5 microL volumes at a concentration of 8 nM and 80nM respectively. The plates are spun at 1k rpm for 1 min and incubated overnight at 4 degrees, then for one hour the subsequent day at room temperature.

Flourescent measurements are read on the Envision 1 plate reader at ICCB-L. The raw data consists of two fluorescence readings - at 665 nm and 620 nm for the acceptor and donor respectively.

Comment: Data analysis:
The raw data consists of two fluorescence readings - at 665 and 620 nm for the acceptor and donor respectively. The data is processed as a ratio of the emission from the acceptor over the donor (homogeneous time resolved fluorescence ratio). Normalized percent inhibition (NPI) for all experimental wells is calculated based on plate averages for negative and positive control HTRF ratio. Positives are scored as any ratio with a 50% or greater inhibition as compared with the positive control (i.e. NEC + Untagged UL50). To be considered a hit, both replicates need to score as positive. Activity scores are derived from NPI, with 100 = 100% inhibition (> 100% set to 100) and 0 = no inhibition (< 0% set to 0). Note that some compounds with NPI <50% (activity scores < 50) are classified as potential hits based on additional criteria (typically by selecting wells with low ratios compared to other experimental wells on the plate).

External ID: MScreen:TargetID_600

Protocol: C-terminally 6xHis tagged CDK2/Cyclin A complex and N-terminally Flag tagged CDC25B C473S (372-566) were expressed and purified. Proteins were incubated together at a final concentration of 125 nM each for 1 hr prior to incubation with compound for 1 hr, followed by addition of anti-6xHis europium cryptate donor beads (Cisbio) and anti-Flag XL-665 acceptor beads (Cisbio) at a final dilution of 1:350 for 1 hr. 20mM potassium fluoride was added 10 minute prior to plate reading. Assay reagents were dispensed using a multidrop liquid dispenser (Thermo Scientific) onto uncoated, black, low-volume, 384-well plates (Corning). Assay plates were quantified using an Envision plate reader (Perkin-Elmer) with excitation of the europium crytate donor at 337 nm wavelength and emission of the donor at 620 nm and emission of the XL-665 acceptor at 665 nm in 18 uL volumes. Assays were performed in a buffer containing 50 mM Tris (pH 7.5), 50 mM NaCl, 10mM MgCl2, 1mM TCEP, with addition of and 1mM ATP, 0.05% BSA, and 0.05% Tween-20 immediately prior to the start of the assay.

Comment: The activity outcome is based on a Z-score (number of standard deviations from the negative control mean) of 3 or higher on at least 50% times that the sample was screened.
For instance, if the sample was screened in n=4 runs, it would be considered active only if it had a Z-score of 3 or above in at least 2 runs.

This screen was funded by NIH grant number: R01CA181185