BCR-ABL initiates mutagenic SSA repair in SAGFP reporter containing BaF3 cells. (A) The SAGFP reporter for SSA consists of the GFP gene fragments 5′GFP and SceGFP3′ separated by a puromycin resistance gene. Repair of the I-SceI–generated DSB in SceGFP3′ by SSA results in a functional GFP gene and excision of the puromycin resistance gene. (B) BaF3.BCR-ABL cells stably expressing the SSA reporter were used to measure repair fidelity in response to I-SceI–induced DSBs. Genomic DNA from clonal populations of GFP⁺ BaF3.BCR-ABL cells containing the reporter was isolated to assess the repaired GFP region by PCR (SAGFP-1 forward and reverse primers indicated by arrows) and sequencing (partial DNA sequence shown).