Do histones bind to a specific group of DNA sequences in chromatin? A test based on DNA ligase action on reconstituted chromatin

Abstract

In the reconstitution of chromatin, the proteins are dissociated from the DNA by exposure to high ionic strength. If such a procedure is carried out in the presence of DNA containing single-strand breaks, the chromatin proteins will redistribute over this nicked DNA as well as over the DNA of the chromatin. When such reconstituted chromatin is created with an excess of DNA ligase, about half of the nicks are sealed. If this partially sealed preparation is taken through a second cycle of reconstitution, a large fraction of the previously unsealed nicks are now sealed upon exposure to the DNA ligase. The changes in the fraction of accessible nicks are in quantitative agreement with a random binding model in which all DNA sequences are equally suitable for binding of histones and rule out the binding of histones to a specific subset of DNA sequences in these model chromatin preparations.