YU238259 is a novel inhibitor of homology-dependent DNA repair(HDR), but does not inhibit non-homologous end-joining (NHEJ), in cell-based GFP reporter assays.

The cloning, expression and purification of USP21 from BL21 (DE3) bacteria are performed using standard molecular biology techniques. USP2, USP5, USP7, USP8, USP28, USP47, Ub-PLA2 (Ub-CHOP) and Ub-EKL (Ub-CHOP2) are generated. Caspase 3 and the caspase 3 substrate DEVD-Rh110 are used. Deubiquitylating enzyme, cathepsin B and 20S proteasome chymotrypsin like protease activities are measured. Caspase 3 activity is determined using a similar protocol. Briefly, dose ranges of compound (including USP7/USP47 inhibitor) are incubated with caspase 3 for 30 minutes before the addition of DEVD-Rh110 and reading on a fluorometric plate reader using excitation and emission maxima of 485 nm and 531 nm respectively. The final concentrations of caspase 3 and DEVD-Rh110 are 2 nM and 100 nM respectively

U2OS cells were pretreated with 25 μM YU238259 or DMSO vehicle for 1 h and cells were then irradiated with 10 Gy IR. Cells were fixed at 8 h post-IR, stained with antibodies and Hoechst dye, and imaged. Foci were quantified using the InCell Analyzer algorithm developed by YCMD. Cells were scored as foci-positive if they contained ≥15 foci (BRCA1, pDNA-PK) or ≥20 foci (53BP1).

Animal Models: 069(nu)/070(nu/+) athymic nude mice. Formulation: 3:1 DMSO:PBS. Dosages: 3 mg/kg . Administration: i.p