Fig. 7.

Comparison of F2 and F1 + F2 in interaction with DNA single-strand breaks. Overlay of [¹⁵N–¹H] HSQC spectra of PARP-1 fragment F1 + F2 and F2 either in the free state (F2, gray peaks; F1 + F2, black peaks) or in the DNA-bound state (F2, orange peaks; F1 + F2, blue peaks). Two expansions are shown in (a) and (b). The two 1:1 protein–DNA complexes (100 μM) were each reconstituted under the same experimental conditions using the 44-nt 5′-phosphorylated DNA dumbbell with a single-stranded nick. DNA binding caused essentially identical chemical shift perturbations for F2 alone (red arrows) as it did for F2 in the context of a two-zinc-finger construct (F1 + F2; blue arrows), as exemplified in the expansions. These data demonstrate that PARP-1 F2 retains the same DNA binding configuration regardless of the presence or absence of F1.