Drug-sensitivity and DNA-binding of a subform of topoisomerase iiα in resistant human HL-60 cells

Fritz Boege*, Harald Biersack, Peter Meyer

*Korrespondierende/r Autor/-in für diese Arbeit
2 Zitate (Scopus)


Topoisomerase IIα (170 kDa) expressed in human HL-60 cells is heterogeneous in charge. By two-dimensional electrophoresis and chromatofocussing two major subforms with pi of 6.5 and 6.7 can be resolved. By preparative anion-exchange chromatography we separated the known topoisomerase II isoenzymes (170/180 kDa) and in addition a late-eluting 170 kDa form, which has not been described before. The catalytic optimum of this late-eluting form is shifted to pH 9.4. It is more than 100-fold resistant to orthovanadate, amsacrine or etoposide, and has an increased salt stability. SDS-treatment induces covalent attachment of this enzyme fraction to calf thymus DNA in the absence of drug. The latter observations indicate an increase in DNA-binding. In the tightly DNA-bound state the late-eluting enzyme is not targeted by cleavable complex forming drugs. Accordingly, cells may become drug-resistant by expressing this form predominantly.

ZeitschriftActa Oncologica
Seiten (von - bis)799-806
PublikationsstatusVeröffentlicht - 1994


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