Stable DNA-protein complexes in eukaryotic chromatin

doi:10.1016/0022-2836(87)90704-2

Journal of Molecular Biology

Volume 196, Issue 2, 20 July 1987, Pages 437-440

https://doi.org/10.1016/0022-2836(87)90704-2 Get rights and content

Abstract

Demembranized sperm and somatic nuclei of mammalian origin were extracted with high salt/urea/2-mercaptoethanol, treated with detergents and purified in CsCl density gradients to isolate DNA. Under these conditions a protein component still remained bound to DNA. This stable DNA-protein complex could be reduced to an oligodeoxynucleotide-peptide complex by extensive sequential digestions with DNase I and Pronase E. Chemical and enzymatic treatments of this complex indicated the presence of a phosphoester bond between DNA and a hydroxyamino acid.

Two-dimensional tryptic peptide mapping revealed a remarkable similarity among the covalently linked protein components in all types of chromatin studied. These maps differed from the maps of mammalian topoisomerases I and II.

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Exposure of fungal conidia ( $Aspergillus$ $ochraceus$ ) or spores of $Bacillus$ $subtilis$ to extreme dryness or vacuum induces DNA lesions, including strand breaks and the formation of DNA-protein cross-links. In wet cells only a small amount of protein is bound to DNA, but exposure to conditions of lowered water activity results in an increasing number of cross-links between DNA and proteins. In fungal conidia these cross-links are detected after selective iodination (¹²⁵J) of the DNA-bound proteins followed by gel electrophoresis and subsequent autoradiography. Another approach is the labelling of DNA with ³²p by means of nick translation and the detection of differences in the electrophoretic mobility of DNA before and after digestion with proteinase K of proteins bound to DNA.
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Journal of Molecular Biology

Letter to the editorStable DNA-protein complexes in eukaryotic chromatin

Abstract

FEBS Letters

Anal. Biochem

J. Biol. Chem

J. Mol. Biol

Progr. Nucl. Acid Res. Mol. Biol

Anal. Biochem

J. Reprod. Fertil

Letter to the editor
Stable DNA-protein complexes in eukaryotic chromatin