FIGURE 2.

Binding of unstructured ssDNA by Ku. A, Ku (1.25, 2.5, 5, 10, and 20 nm) was incubated with oligo(dT)₄₀ (dT; 4 nm) for 10 min. Quantification of results in Fig. 1B (R40) and those pertaining to oligo(dT)₄₀ (T40) binding is shown to the right. B, Ku (5 nm) was incubated with the radiolabeled 40-mer ssDNA (4 nm) for 10 min, and unlabeled oligo(dT)₄₀ (0, 2, 4, 8, and 16 nm) was added, followed by a 10-min incubation. Quantification of the results is shown to the right. C, the substrate was 40-bp dsDNA with a blunt end and a 22-nt 5′-recessed end. PK lanes represent a reaction that was treated with SDS and proteinase K prior to analysis, and asterisks denote the ³²P label. Error bars in A and B represent 1 S.D. based on results from three independent experiments.