Figure 1.

Model system used for evaluating the effects of mismatched base pairs on the stability of the intermediate required for Top1-mediated DNA religation. Top: depiction of the equilibrium between the 10 mer single-stranded DNA and the 39 mer DNA hairpin that constitutes a model system for Top1-mediated DNA religation. A G-X base pair is at the +1 position relative to the Top1 cleavage site. Bottom (a–d): depiction of the steps of Top1 binding, strand dissociation, strand reassociation, and religation.