SOME EFFECTS OF SUBSTITUTING THE DEOXYRIBONUCLEIC ACID OF ISOLATED NUCLEI WITH OTHER POLYELECTROLYTES

Abstract

Up to 75% of the deoxyribonucleic acid of isolated thymocyte nuclei can be removed by incubation with pancreatic deoxyribonuclease. Nuclei so depleted of their DNA lose their capacity for ATP synthesis, for amino acid incorporation into protein, and for adenosine uptake unto nuclear RNAs. The addition of polyanions after DNAase treatment restores much of the biochemical activity of the nucleus. If polyions are present at the time the DNA is removed, substitution can be made for more than 2/3 of the DNA without any apparent loss of activity. The polyanions tested include DNAs, RNAs, and polyadenylic acid and non-nucleotides such as polyethylene sulfonate, heparin, and chondroitin sulfate. Added polycations, such as protamine or polylysine, do not restore function to DNAase-treated nuclei. In addition, polylysine, when added to nuclei whose DNA is still intact, greatly inhibits amino acid uptake into nuclear protein. These findings suggest a correlation between negative charge and the biochemical activity of the nucleus.