Chromosome band 11q23 translocation breakpoints are DNA topoisomerase II cleavage sites.

Cancer Res

Department of Pediatrics, Children's Hospital of Philadelphia, University of Pennsylvania School of Medicine, Pennsylvania 19104, USA.

Published: October 1995

Human leukemias with 11q23 translocations occur sporadically and after cancer treatment with DNA topoisomerase II-targeted drugs. To investigate this process, we examined DNA topoisomerase II cleavage in vitro in subclones of the normal 11q23 genomic homologue and a t(9;11) translocation breakpoint junction. Cleavage was assayed with limiting dilutions of enzyme in the presence or absence of epipodophyllotoxin and ATP. The strongest sites of cleavage coincided with the t(9;11) breakpoint site and two other translocation breakpoint sites within the normal homologue. These results support the involvement of DNA topoisomerase II in the translocation process at chromosome band 11q23.

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