Cells deficient for FKBP25 and the single-strand annealing (SSA) repair factor Rad52 exhibit synthetic loss of viability. (A) Cell counting assay quantifying proliferation in U2OS cells stably expressing shRNA targeting green fluorescent protein (GFP) or FKBP25 and transfected with pooled siRNA targeting Rad52 or a non-targeting control. Error bars represent the standard error of 4 replicates in 2 independent experiments. (B) MTT proliferation assay of U2OS cells transfected with different combinations of siRNA, targeting FKBP25, Rad52, or a non-targeting control. Assay performed 72 h post-transfection. Data points shown are multiple measurements taken from 2 independent experiments. Error bars represent the standard error of 4 measurements across 4 independent transfections. **, P < 0.01; ***, P < 0.001.