title: The arrangement of proteins on the deoxyribonucleic acid in chromatin.
abstract: The arrangement of the protein component on the DNA of the chromatin complex was studied by comparing the rate of release of oligonucleotides and of protein after addition of deoxyribonuclease I and deoxyribonuclease II to rat thymus chromatin. Also the action of deoxyribonuclease I on normal chromatin and on chromatin depleted of non-histone protein was compared, to elucidate the role of the latter protein in chromatin structure. As a preliminary to the above, the rate of action of deoxyribonuclease I on DNA and on chromatin at the same DNA concentration, and the dependence of the action of this enzyme on the Mg(2+) concentration, were studied. It was found that: (1) little if any DNA in chromatin is present in extensive, truly ;free' zones, i.e. completely uncovered by protein; (2) at relatively low concentrations of added Mg(2+), deoxyribonuclease I degrades chromatin more rapidly than DNA; (3) the non-histone protein is not attached directly to the DNA in chromatin.
mesh_terms: D000818:Animals; D002498:Centrifugation; D002843:Chromatin / Q000032:analysis*; D004247:DNA / Q000032:analysis*; D003851:Deoxyribonucleases / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D009691:Nucleic Acid Denaturation; D009698:Nucleoproteins / Q000032:analysis*; D010472:Perchlorates; D011487:Protein Conformation; D051381:Rats; D012965:Sodium Chloride; D012995:Solubility; D013696:Temperature; D013950:Thymus Gland; D013997:Time Factors
chemical_list: D002843:Chromatin; D009698:Nucleoproteins; D010472:Perchlorates; D012965:Sodium Chloride; D004247:DNA; D003851:Deoxyribonucleases; D008274:Magnesium