Mapping of etoposide-mediated Topo-II cleavage sites in T. cruzi chromosome 1. Epimastigotes were treated with 1 mM etoposide for 6 h and chromosomal DNA fractionated by CHEFE and assessed by Southern hybridization. Probes Tc1 and Tc4 were used (Additional data file 5). Large black arrowheads identify the predicted locations of Topo-II activity adjacent to the GC-rich strand-switch domain (yellow oval). The cleavage fragments are identified in red and green. Lane N, non-treated parasites; lane E, etoposide-treated.