CHROMOSOMAL RIBONUCLEIC ACID OF RAT ASCITES CELLS

When chromatin isolated from rat ascites cells is dissociated in the presence of high salt and the chromosomal proteins separated from the deoxyribonucleic acid by buoyant density centrifugation, a portion of the ribonucleic acid contained in the chromatin remains associated with the chromosomal proteins. This ribonucleic acid (chromosomal ribonucleic acid) is characterized by its small size (s20,w = 3.3 S), its high content of dihydroribothymidine, and its ability to form hybrid with about 4% of the nuclear deoxyribonucleic acid. It appears to have no sequences in common with ascites transfer, ribosomal, or messenger ribonucleic acid. A class of ribonucleic acid with similar properties but associated with the cytoplasmic proteins has also been isolated. This ribonucleic acid hybridizes to about 2% of the nuclear deoxyribonucleic acid and contains very few, if any, sequences not also contained in chromosomal ribonucleic acid. This fraction of ribonucleic acid is however unable to compete with about 50% of the sequences present in chromosomal ribonucleic acid indicating that a large portion of chromosomal ribonucleic acid is confined to the chromatin. A further class of ribonucleic acid associated with the nuclear sap proteins appears to be identical with the ribonucleic acid associated with cytoplasmic proteins. © 1969, American Chemical Society. All rights reserved.