Topoisomerase II, not topoisomerase I, is the proficient relaxase of nucleosomal DNA
- 18 May 2006
- journal article
- Published by Springer Science and Business Media LLC in The EMBO Journal
- Vol. 25 (11), 2575-2583
- https://doi.org/10.1038/sj.emboj.7601142
Abstract
Eukaryotic topoisomerases I and II efficiently remove helical tension in naked DNA molecules. However, this activity has not been examined in nucleosomal DNA, their natural substrate. Here, we obtained yeast minichromosomes holding DNA under (+) helical tension, and incubated them with topoisomerases. We show that DNA supercoiling density can rise above +0.04 without displacement of the histones and that the typical nucleosome topology is restored upon DNA relaxation. However, in contrast to what is observed in naked DNA, topoisomerase II relaxes nucleosomal DNA much faster than topoisomerase I. The same effect occurs in cell extracts containing physiological dosages of topoisomeraseI and II. Apparently, the DNA strand‐rotation mechanism of topoisomerase I does not efficiently relax chromatin, which imposes barriers for DNA twist diffusion. Conversely, the DNA cross‐inversion mechanism of topoisomerase II is facilitated in chromatin, which favor the juxtaposition of DNA segments. We conclude that topoisomerase II is the main modulator of DNA topology in chromatin fibers. The nonessential topoisomerase I then assists DNA relaxation where chromatin structure impairs DNA juxtaposition but allows twist diffusion.This publication has 75 references indexed in Scilit:
- The probabilities of supercoil removal and decatenation by yeast DNA topoisomerase IIGenes to Cells, 1996
- The Twist, Writhe and Overall Shape of Supercoiled DNA Change During Counterion-induced Transition from a Loosely to a Tightly Interwound Superhelix: Possible Implications for DNA Structure in VivoJournal of Molecular Biology, 1994
- Localization of RAP1 and topoisomerase II in nuclei and meiotic chromosomes of yeastThe Journal of cell biology, 1992
- Structure of plectonemically supercoiled DNAJournal of Molecular Biology, 1990
- Function of DNA topoisomerases as replication swivels in Saccharomyces cerevisiaeJournal of Molecular Biology, 1989
- A subthreshold level of DNA topoisomerases leads to the excision of yeast rDNA as extrachromosomal ringsCell, 1989
- Mitotic recombination in the rDNA of S. cerevisiae is suppressed by the combined action of DNA topoisomerases I and IICell, 1988
- Metaphase chromosome structure: Involvement of topoisomerase IIJournal of Molecular Biology, 1986
- Nuclease digestion of circular TRP1ARS1 chromatin reveals positioned nucleosomes separated by nuclease-sensitive regionsJournal of Molecular Biology, 1984
- Torsional rigidity of DNA and length dependence of the free energy of DNA supercoilingJournal of Molecular Biology, 1984