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Nucleic Acids Research, 1991, Vol. 19, No. 25 7139-7144
© 1991

Foreword

Interactions of Drosophilla DNA topoisomerase II with left-handed Z-DNA in supercoiled minicircles

Gerardo C. Glikin+, Thomas M. Jovin and Donna J. Arndt-Jovin*

DEpartment of Molecular Biology, Max Planck Institute for Biophysical Chemistry Postfach 2841, D-3400 Göttingen, FRG

*To whom correspondence should be addressed

The native form of Drosophila melanogaster DMA topoisomerase II was purified from Schneider's S3 tissue culture cells and studied with two supercoiled minicircle preparations, mini and mini-CG, 354 bp and 370 bp in length, respectively. Mini-CG contains a d(CG)7 Insert which assumes a left-handed Z-DNA conformation in negative supercoiled topoisomers with a negative linking number difference -{Delta}Lk>s 2. The interactions of topoisomerase II with topoisomer families of mini and mini-CG were studied by band-shift gel electrophoresls in which the individual topoisomer and their discrete or aggregated protein complexes were resolved. A monocolonal anti-Z-DNA IgG antibody (23BS) bound and aggregated only mini-CG, thereby confirming the presence of Z-DNA. Topoisomerase II bound and relaxed mini-CG more readily than mini. In both cases, there was a preference for more highly negatively supercoiled topoisomers. The topoisomerase II inhibitor VM-26 induced the formation of stable covalent DNA-protein intermediates. In addition, the non-hydrolyzable GTP analogue GTP{gamma}S inhibited the binding and relaxation activities. Experiments to detect topoisomerase cleavage sites failed to elicit specific loci on either minicircle preparation. We conclude that Drosophila topoisomerase II is able to bind and process small minicircles with lengths as short as 360 bp and negative superhelln densities, -{sigma}, which can exceed 0.1. Furthermore, the enzyme has a preferential affinity for topoisomers containing Z-DNA segments and relaxes these molecules, presumably by cleavage external to the inserts. Thus, a potentially functional relationship between topoisomerase II, an enzyme regulating the topological state of DNA-chromatin in vivo, and lefthanded Z-DNA, a conformation stabilized by negative supercoiling, has been established.

+Permanent address: Instituto de Investigaciones en Ingenierfa Geneuca y Biologfa Molecular (Consejo NacionaJ de Invcstigaciones Cientfficas y Tecnicas) y Facultad de Ciencias Exactas y Naturales (Universidad de Buenos Aires), 1428 Buenos Aires, Argentina


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This article has been cited by other articles:


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A. Herbert and A. Rich
The Biology of Left-handed Z-DNA
J. Biol. Chem., May 17, 1996; 271(20): 11595 - 11598.
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P Buchenau, H Saumweber, and D. Arndt-Jovin
Consequences of topoisomerase II inhibition in early embryogenesis of Drosophila revealed by in vivo confocal laser scanning microscopy
J. Cell Sci., January 4, 1993; 104(4): 1175 - 1185.
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