Figure 4.

Efficient NHEJ requires Ku70, DNA ligase 4, and MRN. KRP 3-4 cells bearing no mutation (WT) or the indicated mutations were tested in the excision assay. Ten individual colonies for each strain were tested by two rounds of PCR. Lane “C” contains various amounts of a PCR product from wild-type DNA loaded as a size marker for the expected NHEJ fragment. The WT gels are the same as those shown in Figure 2B. The median excision frequencies and footprint sequences are shown in Figure 5 and Figure S5 in File S1, respectively. MRN, Mre11-Rad50-Nbs1; NHEJ, nonhomologous end-joining; wild-type, WT.