Studies on nucleic acids in Rous sarcoma virus-induced mouse ascites sarcoma cells. Distribution and electron microscopy of nucleic acids in subcellular fractions and circular DNA in mitochondrial fraction

For the purpose to clarify the distribution of DNA in mouse ascites sarcoma cells (SR-C3H) induced by Rous sarcoma virus (Schmidt-Ruppin strain), quantitative assays were carried out by SCHMIDT-THANNHAUSERSCHNEIDER'S method using subcellular fractions isolated from SR-C3H cells and C3H mouse liver as a control tissue, and simultaneously electron microscopic observations were conducted with the rotary shadowed preparations of the SDS-phenol extracted nucleic acids by the protein monolayer technique. The results are briefly summarized as follows. 1. The RNA/DNA ratios in SR-C3H cells and liver cells were 2.3 and 3.7, while those in nuclear fraction of SR-C3H cells and liver cells were 0.34 and O. 56, respectively. The electron micrographs of nuclear nucleic acids revealed a DNA-RNA complex-like structure. 2. DNA and RNA contents of SR-C3H mitochondria were found to be 3.1 and 24 fl-g per mg of protein, respectiVely, which proved to be greater than those of liver mitochondria. The mean values of the contour length of circular DNA molecules in highest frequency group observed in the electron micrographs were 4.88 μ. in SR-C3H mitochondria and 5.08 μ. in mouse liver mitochondria. There could be observed circular molecules of duplicated-length in both mitochondrial DNA's and small circular molecules in SR-C3H mitochondrial DNA. 3. In the microsomal and supernatant fractions of SR-C3H cells and mouse liver cells, the ratios of DNA to RNA gave several percent by chemical analysis and this percentage was particularly high in the supernatant of SR-C3H cells. On the other hand, in the electron micrographs, the fibrous structure was significantly recovered in the supernatant nucleic acids of SR-C3H cells, but with difficulty in the other three fractions. This fibrous structure measured 1.13 μ in the mean value of the length and was considered to be DNA as it readily disappeared after the treat· ment with DNase.