Unwinding of nucleosomal DNA by a DNA helicase

A. K. Eggleston, T. E. O'Neill, E. M. Bradbury, S. C. Kowalczykowski

Research output: Contribution to journalArticlepeer-review

35 Scopus citations


We have asked whether a DNA helicase can unwind DNA contained within both isolated native chromatin and reconstituted chromatin containing regularly spaced arrays of nucleosome cores on a linear tandem repeat sequence. We find that Escherichia coli recBCD enzyme is capable of unwinding these DNA substrates and displacing the nucleosomes, although both the rate and the processivity of enzymatic unwinding are inhibited (a maximum of 3- and >25- fold, respectively) as the nucleosome density on the template is increased. The observed rate of unwinding is not affected if the historic octamer is chemically cross-linked; thus, dissociation, or splitting, of the histone octamer is not required for unwinding to occur. The unwinding of native chromatin isolated from HeLa cell nuclei occurs both in the absence and in the presence of linker historic H1. These results suggest that as helicases unwind DNA, they facilitate nuclear processes by acting to clear DNA of histones or DNA-binding proteins in general.

Original languageEnglish (US)
Pages (from-to)2024-2031
Number of pages8
JournalJournal of Biological Chemistry
Issue number5
StatePublished - 1995

ASJC Scopus subject areas

  • Biochemistry


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