The Properties and the Enzymatic Degradation of Desoxyribonucleoprotein from Liver Cell Nuclei

The isolation and properties of a desoxyribonucleoprotein of the rat liver cell nucleus are described. This material consists of DNA (desoxyribonucleic acid) bound to the residual chromosomal protein by what appear to be covalent linkages. Lipide is present, but can be removed by extraction in lipide solvents prior to isolation of the nucleoprotein, without much change in the physical properties of the latter. The nucleoprotein in question forms elastic, recoilable gels in molar saline at pH 7.0 or in water at pH 8.0 to 10.0 or even higher, which are similar to those that can be obtained from whole nuclei. The effects of x-rays, heat, and enzymes on the nucleoprotein are discussed, and the composition of the protein component is investigated. The latter contains an "occult" protein that can be liberated by heating in 0.1 N HCl. A study of the enzymatic degradation of the desoxyribonucleoprotein has been made, with the aim of attempting the isolation of small polynucleotide fragments attached to amino acids or short peptides that might be useful in characterizing the mode of attachment of the desoxyribonucleic acid to the protein in the desoxyribonucleoprotein. Evidence is presented indicating that such products can be isolated through the use of electrophoresis on paper.