FIG. 6.

I3-DNA interaction: NaCl titration and competition analyses. (A) The interaction of I3 with ssDNA is salt resistant. Reaction mixtures containing 3.3 pmol of recombinant I3 and 0.2 pmol of radiolabeled single-stranded 24-mer were incubated at 30°C for 15 min in buffer containing the indicated concentration of NaCl. Samples were fractionated on a 15% nondenaturing polyacrylamide gel at 4°C and visualized by autoradiography. (B) The interaction of I3 with ssDNA can be reversed by the addition of unlabeled competitor DNA. Reaction mixtures containing 3.3 pmol of recombinant I3 and 0.2 pmol radiolabeled single-stranded 24-mer were incubated at 30°C for 15 min. Unlabeled single-stranded 24-mer was then added to the levels indicated, and reaction mixtures were incubated for an additional 15 min at 30°C. Samples were then fractionated on a 15% nondenaturing polyacrylamide gel at 4°C and visualized by autoradiography.