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. 1999 Jun 22;96(13):7196–7201. doi: 10.1073/pnas.96.13.7196

Figure 4.

Figure 4

Et743 induces top1-mediated DNA single-strand breaks. SV40 DNA was reacted with top1 in the absence or presence of drugs, as indicated. Reactions were stopped with 0.5% SDS followed by proteinase K incubation. Samples were run in 1% agarose gels containing ethidium bromide. Percent nicked DNA was computed after FluorImager analysis (Molecular Dynamics) by using the imagequant software and is indicated below each lane. (A) top1-mediated nicking assay by using supercoiled negative SV40 DNA. Lane 1, DNA alone; lane 2, + top1; and lanes 3–6, + top1 and the indicated concentrations of Et743 or CPT. (B) Et743 induces more top1-mediated DNA nicking in supercoiled than in linear SV40 DNA. Lanes 1 and 5, DNA alone; lanes 2 and 6, DNA + top1; lanes 3 and 7, DNA + top1 + Et743 (0.1 μM); lanes 4 and 8, Et743 without top1. (C) Et743 does not induce detectable top2 cleavage complexes. Lane 1, DNA alone; lane 2, + top2; and lanes 3–4, + top2 and the indicated drug concentrations.