FIG. 3.

Blunt ligation is favored over heterologous flap ligation. Reaction of the 5′-tailed 3′-blunt covalent topoisomerase-DNA intermediate with acceptor A was performed as described in Materials and Methods. The reaction products were analyzed by polyacrylamide gel electrophoresis. An autoradiogram of the gel is shown in the left panel. The strand transfer reaction times are specified above the lanes. ", seconds; ′, minutes. A control reaction mixture containing the 5′ ³²P-labeled 60-mer substrate and no topoisomerase was analyzed in lane −. The positions of the radiolabeled 66-mer blunt recombinant, 48-mer flap recombinant, and covalent DNA-peptide adducts are indicated. The extents of recombinant formation (as percentages of total labeled DNA) are plotted as a function of time in the right panel. The reaction pathway is illustrated at the top and discussed in the text.