(A) SPOP forms nuclear foci after induction of DNA damage by γ-irradiation (3GY) in prostate cells derived from transgenic mice (MPC) and human LNCaP cells. Red represents nuclear Spop protein foci. Blue represents nuclear DNA stained with DAPI. (B) MPC expressing Cre-inducible SPOP-F133V was infected with tamoxifen-inducible Cre (CreERT2), and DNA damage was assessed after IR with comet assays. Inset: representative cells showing comet tails after IR. (C, D, E) Quantification of γH2AX, 53BP1, or RAD51 foci in RWPE cells overexpressing WT or F133V mutant SPOP after camptothecin (CPT) (1 μM) induced DNA damage. Time indicates the observation interval in minutes including double strand break (DSB) induction (0–60 min) and recovery (60–180 min). Shown are the percentages of cells for each genotype with more than 5 foci per nucleus. Results are represented as s.e.m. (F) Representative pictures showing γH2AX, RAD51, or 53BP1 foci (red or green). Blue represents nuclear DNA stained with DAPI. (G) Quantification of Rad51 foci in γ-irradiated (2GY) MPC with tamoxifen-inducible SPOP-F133V. Rad51 foci were counted 30 min post irradiation. (H) Representative pictures showing Rad51 foci in mouse prostate epithelial cells before and after γ-irradiation (2GY). (I) Quantification of RAD51 foci in RWPE cells treated with siSPOP or control siRNA and subsequently exposed to CPT (1 μM, 1 hr).