Base Compositions of RNA of Nuclear Fractions Obtained by Sequential Extraction with Saline Solutions I

Nuclear preparations of the Walker 256 carcinosarcoma, Novikoff hepatoma, Morris hepatoma 7794, and Morris hepatoma 9108 were successively extracted with 0.15 M and 2 ~ NaC1 solutions to obtain the "nuclear sap" and "DNA" or chromatin fractions, respectively; the residue fraction contains much of the nucleolar RNA as well as other RNA of the nuclear ribonucleoprotein network (24). The RNA prepared from these extracts was characterized by density gradient sedimentation; nucleotide compositions were determined by optical density and 32p base analysis. The orthophosphate-32P was injected 20 minutes before the animals were sacrificed. The a2p base compositions of the RNA of the DNA-RNA fraction derived from the " D N A " or chromatin fraction differed from that of the nuclear residue fraction in their higher content of adenylic acid and lower content of guanylic acid. Although the UV base compositions of the DNA-RNA and nuclear residue fractions were similar, the former had a slightly higher content of adenylic acid. In the tumors, both the ~2p base compositions of the RNA of the residue fractions and the 'DNA-RNA fractions differed from those of normal liver. In both, the values for adenylic acid were significantly lower than those found in normal liver. In the residue fraction, the guanylic acid content was lower in the normal liver than in the tumors. These results are in agreement with the data reported in earlier studies on isolated nuclei and nucleoli and indicate that in the tumors the base composition of RNA synthesized in the extranucleolar chromatin, as well as that of the nucleolar RNA, differs from that of the normal liver.