Fig. 4.

In vitro formation of TOP1ccs in a duplex oligonucleotide DNA containing 6–4PPs. (A) The sequence of a duplex DNA containing a 6–4PP is shown with its respective control. The 6–4PP site is highlighted by red. Star indicates ³²P label at the 3′ end of either upper strand or lower strand. The arrows marked a–e show the positions of TOP1cc sites detected in B. (B) The representative TOP1 cleavage assay using oligonucleotides shown in A. (Left) Analysis of the upper strand and (Right) analysis of the lower strand shown in A. Following an incubation of the oligonucleotides with TOP1, they were subjected to denaturing polyacrylamide gel electrophoresis followed by autoradiography. The arrowheads marked (a–e) correspond to the TOP1 cleavage sites marked with a–e in A. The numbers shown as individual arrowheads represent the length of nucleotides from the 3′-³²P label. The most prominent TOP1 cleavage site is indicated by the pink arrow with annotation b in A, Left.