STUDIES ON INTRANUCLEAR DISTRIBUTION AND PROPERTIES OF MOUSE SATELLITE DNA

Nucleoli isolated from mouse strain L-cells, L-5178Y lymphoblast tumor cells, and mouse liver and kidney cells showed a 3-4-fold enrichment in satellite DNA when compared with DNA from whole nuclei. This amount of satellite DNA associated with the nucleoli accounted for approximately one-third of the total satellite DNA of the cell. Treating the nucleoli with 2 M NaCl removed more main band DNA than satellite, and suggested that satellite DNA was more intimately bound to the nucleoli than main band DNA. However, attempts to demonstrate whether the satellite enrichment could have been due to preferential adsorption to the nucleoli during their isolation were inconclusive. Incubation of native or renatured satellite DNA with Escherichia coli exonuclease I did not produce any change in its buoyant density in CsCl. The base composition of satellite DNA was determined by using three different combinations of enzymes. Incubation with E. coli exonuclease III produced an increase in CsCl buoyant density and converted 45% of the satellite DNA to mononucleotides having the same average base composition as the total DNA. The satellite DNA did not behave differently from the main band DNA towards the deoxyribonucleases used in this study. © 1968.