Histone octamer instability under single molecule experiment conditions

Cyril Claudet, Dimitar Angelov, Philippe Bouvet, Stefan Dimitrov, Jan Bednar

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We have studied the sample concentration-dependent and external stress-dependent stability of native and reconstituted nucleosomal arrays. Whereas upon stretching a single chromatin fiber in a solution of very low chromatin concentration the statistical distribution of DNA length released upon nucleosome unfolding shows only one population centered around ∼25 nm, in nucleosome stabilizing conditions a second population with average length of ∼50 nm was observed. Using radioactively labeled histone H3 and H2B, we demonstrate that upon lowering the chromatin concentration to very low values, first the linker histones are released, followed by the H2A-H2B dimer, whereas the H3-H4 tetramer remains stably attached to DNA even at the lowest concentration studied. The nucleosomal arrays reconstituted on a 5 S rDNA tandem repeat exhibited similar behavior. This suggests that the 25-nm disruption length is a consequence of the histone H2A-H2B dimer dissociation from the histone octamer. In nucleosome stabilizing conditions, a full ∼145 bp is constrained in the nucleosome. Our data demonstrate that the nucleosome stability and histone octamer integrity can be severely degraded in experiments where the sample concentration is low.

Original languageEnglish
Pages (from-to)19958-19965
Number of pages8
JournalJournal of Biological Chemistry
Issue number20
Publication statusPublished - 20 May 2005
Externally publishedYes


ASJC Scopus subject areas

  • Biochemistry

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