Mitotic chromosomes are constrained by topoisomerase II-sensitive DNA entanglements

Ryo Kawamura, Lisa H. Pope, Morten O. Christensen, Mingxuan Sun, Ksenia Terekhova, Fritz Boege, Christian Mielke, Anni H. Andersen, John F. Marko

Research output: Contribution to journalArticlepeer-review

43 Scopus citations


We have analyzed the topological organization of chromatin inside mitotic chromosomes. We show that mitotic chromatin is heavily selfentangled through experiments in which topoisomerase (topo) II is observed to reduce mitotic chromosome elastic stiffness. Single chromosomes were relaxed by 35% by exogenously added topo II in a manner that depends on hydrolysable adenosine triphosphate (ATP), whereas an inactive topo II cleavage mutant did not change chromosome stiffness. Moreover, experiments using type I topos produced much smaller relaxation effects than topo II, indicating that chromosome relaxation by topo II is caused by decatenation and/or unknotting of double-stranded DNA. In further experiments in which chromosomes are first exposed to protease to partially release protein constraints on chromatin, ATP alone relaxes mitotic chromosomes. The topo II-specific inhibitor ICRF-187 blocks this effect, indicating that it is caused by endogenous topo II bound to the chromosome. Our experiments show that DNA entanglements act in concert with protein-mediated compaction to fold chromatin into mitotic chromosomes.

Original languageEnglish (US)
Pages (from-to)653-663
Number of pages11
JournalJournal of Cell Biology
Issue number5
StatePublished - Mar 8 2010

ASJC Scopus subject areas

  • Cell Biology


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