NDLI: Topoisomerase II, not topoisomerase I, is the proficient relaxase of nucleosomal DNA

Content Provider	PubMed Central
Author	Salceda, Javier Fernández, Xavier Roca, Joaquim
Copyright Year	2006
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.
Related Links	http://dx.doi.org/10.1038/sj.emboj.7601142
Ending Page	2583
Page Count	9
Starting Page	2575
File Format	PDF
ISSN	02614189
e-ISSN	14602075
Journal	The EMBO Journal
Issue Number	11
Volume Number	25
Language	English
Publisher Date	2006-06-07
Access Restriction	Open
Subject Keyword	Biochemistry, Genetics and Molecular Biology(all) Immunology and Microbiology(all) Neuroscience(all) Molecular Biology Research in Higher Education
Content Type	Text
Resource Type	Article
Subject	Neuroscience Immunology and Microbiology Medicine Molecular Biology

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