The DNA covalently linked with Top1 purified by immuno‐pull‐down (after proteinase K digestion) was further treated with 3 μM recombinant TDP1 overnight or mock‐treated (Huang
et al,
2013). TDP1‐treated DNA showed increased gel mobility. The control DNA was purified from the same sample after the immuno‐pull‐down procedure and TDP1 treatment showed no effect on the control DNA.