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Nucleic Acids Research Advance Access published online on September 29, 2008
Nucleic Acids Research, doi:10.1093/nar/gkn640
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© 2008 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Nucleic Acid Enzymes

Hairpin structures formed by alpha satellite DNA of human centromeres are cleaved by human topoisomerase II{alpha}

Anette Thyssen Jonstrup1, Tina Thomsen1, Yong Wang1, Birgitta R. Knudsen1, Jørn Koch2 and Anni H. Andersen1,*

1Department of Molecular Biology, University of Aarhus, C. F. Møllers Allé, Building 130 and 2Institute of Patology, University of Aarhus, Nørrebrogade 44, Aarhus, Denmark

*To whom correspondence should be addressed. Tel: +45 8942 2600; Fax: +45 8942 2612; Email: aha{at}mb.au.dk

Received June 25, 2008. Revised September 16, 2008. Accepted September 17, 2008.

Although centromere function has been conserved through evolution, apparently no interspecies consensus DNA sequence exists. Instead, centromere DNA may be interconnected through the formation of certain DNA structures creating topological binding sites for centromeric proteins. DNA topoisomerase II is a protein, which is located at centromeres, and enzymatic topoisomerase II activity correlates with centromere activity in human cells. It is therefore possible that topoisomerase II recognizes and interacts with the alpha satellite DNA of human centromeres through an interaction with potential DNA structures formed solely at active centromeres. In the present study, human topoisomerase II{alpha}-mediated cleavage at centromeric DNA sequences was examined in vitro. The investigation has revealed that the enzyme recognizes and cleaves a specific hairpin structure formed by alpha satellite DNA. The topoisomerase introduces a single-stranded break at the hairpin loop in a reaction, where DNA ligation is partly uncoupled from the cleavage reaction. A mutational analysis has revealed, which features of the hairpin are required for topoisomerease II{alpha}-mediated cleavage. Based on this a model is discussed, where topoisomerase II interacts with two hairpins as a mediator of centromere cohesion.

Present address: Yong Wang, Immunogen Inc., 830 Winter Street, Waltham, MA 02451, USA.


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