Single chromatin fiber stretching reveals physically distinct populations of disassembly events

L.H. Pope, Martin L. Bennink, K.A. van Leijenhorst-Groener, D.N. Nikova, Jan Greve, J.F. Marko

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Abstract

Eukaryotic DNA is packaged into the cell nucleus as a nucleoprotein complex, chromatin. Despite this condensed state, access to the DNA sequence must occur during gene expression and other essential genetic events. Here we employ optical tweezers stretching of reconstituted chromatin fibers to investigate the release of DNA from its protein-bound structure. Analysis of fiber length increase per unbinding event revealed discrete values of ~30 and ~60 nm. Furthermore, a loading rate analysis of the disruption forces revealed three individual energy barriers. The heights of these barriers were found to be ~20 kBT, ~25 kBT, and ~28 kBT. For subsequent stretches of the fiber it was found that events corresponding to the ~28 kBT energy barrier were significantly reduced. No correlation between energy barrier crossed and DNA length release was found. These studies clearly demonstrate that optical tweezers stretching of chromatin provides insight into the energetic penalties imposed by chromatin structure. Furthermore these studies reveal possible pathways via which chromatin may be disrupted during genetic code access.
Original languageEnglish
Pages (from-to)3572-3583
Number of pages12
JournalBiophysical journal
Volume88
Issue number5
DOIs
Publication statusPublished - 2005

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Chromatin
Optical Tweezers
Population
DNA
Genetic Code
Nucleoproteins
Cell Nucleus
Gene Expression
Proteins

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Pope, L. H., Bennink, M. L., van Leijenhorst-Groener, K. A., Nikova, D. N., Greve, J., & Marko, J. F. (2005). Single chromatin fiber stretching reveals physically distinct populations of disassembly events. Biophysical journal, 88(5), 3572-3583. https://doi.org/10.1529/biophysj.104.053074
Pope, L.H. ; Bennink, Martin L. ; van Leijenhorst-Groener, K.A. ; Nikova, D.N. ; Greve, Jan ; Marko, J.F. / Single chromatin fiber stretching reveals physically distinct populations of disassembly events. In: Biophysical journal. 2005 ; Vol. 88, No. 5. pp. 3572-3583.
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Pope, LH, Bennink, ML, van Leijenhorst-Groener, KA, Nikova, DN, Greve, J & Marko, JF 2005, 'Single chromatin fiber stretching reveals physically distinct populations of disassembly events' Biophysical journal, vol. 88, no. 5, pp. 3572-3583. https://doi.org/10.1529/biophysj.104.053074

Single chromatin fiber stretching reveals physically distinct populations of disassembly events. / Pope, L.H.; Bennink, Martin L.; van Leijenhorst-Groener, K.A.; Nikova, D.N.; Greve, Jan; Marko, J.F.

In: Biophysical journal, Vol. 88, No. 5, 2005, p. 3572-3583.

Research output: Contribution to journalArticleAcademicpeer-review

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AU - Pope, L.H.

AU - Bennink, Martin L.

AU - van Leijenhorst-Groener, K.A.

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AU - Marko, J.F.

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AB - Eukaryotic DNA is packaged into the cell nucleus as a nucleoprotein complex, chromatin. Despite this condensed state, access to the DNA sequence must occur during gene expression and other essential genetic events. Here we employ optical tweezers stretching of reconstituted chromatin fibers to investigate the release of DNA from its protein-bound structure. Analysis of fiber length increase per unbinding event revealed discrete values of ~30 and ~60 nm. Furthermore, a loading rate analysis of the disruption forces revealed three individual energy barriers. The heights of these barriers were found to be ~20 kBT, ~25 kBT, and ~28 kBT. For subsequent stretches of the fiber it was found that events corresponding to the ~28 kBT energy barrier were significantly reduced. No correlation between energy barrier crossed and DNA length release was found. These studies clearly demonstrate that optical tweezers stretching of chromatin provides insight into the energetic penalties imposed by chromatin structure. Furthermore these studies reveal possible pathways via which chromatin may be disrupted during genetic code access.

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