RAD51(Y315F) mutant displayed reduced nuclear foci formation and inhibited HomeoRR in BCR-ABL1-positive leukemia cells. (A) Top panel: Western blot showing the expression of Flag-tagged RAD51 proteins in BCR-ABL1–32Dcl3-pLB4 cells transfected with Flag-RAD51(WT) and Flag-RAD51(Y315F) expression plasmids or with empty (E) plasmid. Bottom panel: Cells were irradiated with 4 Gy; and 3 hours later, RAD51(WT) and RAD51(Y315F) nuclear foci were detected by immunofluorescence with anti-Flag antibody. Representative nuclei are shown; nuclei borders are marked in blue. (B) Data are number of Flag-RAD51(WT) and Flag-RAD51(Y315F) foci/cell ± SD in nonirradiated (Control) and 4 Gy-irradiated cells. *P < .001 versus corresponding WT group (Student t test). (C) HomeoRR activity in I-SceI transfected DsRed1-Mito⁺ cells. Data are percentage of G418-resistant clones ± SD. *P < .001 (Student t test).