FIG. 5.
PARP1 and 53BP1 function in the repair of HU-induced DSBs but are dispensable for the repair of MMC-induced DSBs. (A to C) B cells of the indicated genotypes were treated with 0.25 mM HU for 15 h, and metaphases were obtained after an 8-h washout period. Chromosomes were hybridized with a telomere-specific (TTAGG)3 PNA probe, and chromosomal aberrations were scored in 30 metaphases per sample. The percentage of metaphases containing at least one chromosomal aberration (A) and the number of aberrations per metaphase (B) are shown. (C) Representative examples of partial metaphases; the yellow arrows point to chromatid breaks and fusions. Red, (TTAGGG)3 probe; blue, DAPI. (D and E) Activated B cells of the indicated genotypes were treated with MMC at the indicated doses for 36 h, and metaphases were scored for aberrations via telomere FISH. The percentage of metaphases containing at least one chromosomal aberration (D) and the number of aberrations per metaphase (E) are shown. For all experiments, the bars represent the averages and standard deviations of 3 to 5 mice per genotype in 3 independent experiments.