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. Author manuscript; available in PMC: 2013 Feb 28.
Published in final edited form as: Biochemistry. 2012 Feb 10;51(8):1730–1739. doi: 10.1021/bi201159b

Figure 8.

Figure 8

Enhancement of topoisomerase IIα-mediated DNA cleavage by the detached m-AMSA head group. Panel A shows the effects of the isolated m-AMSA head group (structure shown as inset) on the cleavage of negatively supercoiled plasmid DNA by human topoisomerase IIα. determined. Panel B shows a series of control experiments that confirm that DNA cleavage induced by the isolated head group is mediated by human topoisomerase IIα. Reactions contained DNA and enzyme in the absence of m-AMSA head group (TIIα), DNA and 3 mM head group in the absence of enzyme, or complete reaction mixtures treated with SDS prior to adding EDTA (SDS). The reversibility of DNA cleavage induced by 3 mM head group was determined by incubating reactions with EDTA prior to trapping cleavage complexes with SDS (EDTA). To determine whether DNA cleavage induced by 3 mM head group was protein-linked, proteinase K treatment was omitted (−ProK). Error bars for both panels represent standard deviations for three independent experiments.