Ccnd1+/+ and Ccnd1KI/KIMAF lines were grown in serum-proficient media for 24 h. Cells were then treated with control DMSO or 2.5 μM of the PARP inhibitor ABT-888. One hour post-treatment, the indicated lines were treated with 5 Gy of radiation. Cells were then allowed to recover for 48 h, after which BrdU was added for 1 h, and then harvested for bivariate flow cytometry. Representative traces for each condition are shown (left) and BrdU incorporation of biological triplicates was quantified (right). 