title: DNA-protein interactions of the rat liver non-histone chromosomal protein.
abstract: Native rat liver NHC protein-DNA interactions have been investigated by use of a nitrocellulose filter assay sensitive in detection of protein-DNA complexes. Optimal conditions for DNA-protein interactions occurs at low ionic strength conditions (110 mM phosphate buffer). A fraction of NHC proteins was enriched 25-fold by their affinity for rat DNA immobilized on cellulose columns under these conditions. At higher ionic strength (260 mM-0.04M phosphate buffer and 0.15 M sodium chloride), this fraction binds approximately sevenfold less to rat DNA but with a substantial increase in stability of the complexes. Equilibrium competition experiments indicate that at the higher ionic strength there is a considerable DNA sequence specificity of the rat DNA binding NHC protein. Since rat DNA contains three components as defined by their reassociation kinetics: single copy DNA (C0t1/2pure = 1.6 times 103); middle repetitive DNA (C0t1?1PURE = 1.1); and highly repetitive (C0t1/2pure smaller than 0.02). The two former were isolated and employed in the DNA binding assays. At the high ionic strength criterion, the rat DNA binding NHC proteins showed a substantial preference for a subset of middle repetitive DNA sequences. This suggests a preferential interaction between a class of NHC proteins and a class of middle repetitive DNA sequences.
mesh_terms: D000818:Animals; D001202:Ascitic Fluid / Q000032:analysis; D001665:Binding Sites; D002875:Chromosomes / Q000032:analysis*; D004247:DNA; D004269:DNA, Bacterial; D004926:Escherichia coli; D007700:Kinetics; D008099:Liver / Q000032:analysis*; D046911:Macromolecular Substances; D009698:Nucleoproteins; D009994:Osmolar Concentration; D011485:Protein Binding; D051381:Rats; D013045:Species Specificity; D013997:Time Factors
chemical_list: D004269:DNA, Bacterial; D046911:Macromolecular Substances; D009698:Nucleoproteins; D004247:DNA