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Comparative Studies on Nuclei and Chromatin of Hepatomas and Rat Liver¹

McArdle Laboratory, Medical School, University of Wisconsin, Madison, Wisconsin 53706

Comparative studies on nuclei and chromatin of hepatomas and rat liver were performed because of reports that malignant tumors contain higher amounts of acidic nuclear proteins than nonmalignant tissues. The studies involved the protein composition of nuclei and chromatin, the amounts of total nuclear and chromosomal RNA, the phosphate content of nuclear proteins, thermal denaturation experiments with chromatin preparations, and experiments on the template activities of chromatin in a DNA polymerase system. No differences were found in the chemical composition of nuclei or chromatin between hepatoma 5123C and host liver. Novikoff cells showed increased amounts of residual nuclear protein and total nuclear and chromosomal RNA. The phosphate content of nuclear proteins of hepatoma 5123C was found to be very close to that of host liver. The phosphorylation of the histones and chromosomal nonhistone proteins of Novikoff cells was found to be lower than that of hepatoma 5123C and host liver. Thermal denaturation experiments revealed nearly identical temperatures of half-melting (T_m) and total hyperchromicities for chromatin preparations of hepatoma 5123C, host liver, and Novikoff cells. The template activities of chromatin of hepatoma 5123C and hepatoma 7800 were found to be lower than the template activities of chromatin of their host livers. Chromatin of Novikoff cells showed a lower template activity than chromatin of normal liver.

¹ This investigation was supported in part by Departmental Grant CA-07175 and Training Grant TO1-CA-5002 from the National Cancer Institute, USPHS.

² USPHS International Postdoctoral Fellowship FO5-1126, 1966 to 1968. Present address: Biochemisches Institut der Universitat, Hermann Herder Strasse 7, 78 Freiburg, Germany.

³ Laboratory of Biochemistry, National Cancer Institute, Bethesda, Md. 20014. Supported in part by USPHS Grant CA-10729. Present address: Department of Biochemistry, College of Medicine, Howard University, Washington, D. C. 20001.

Received 4/22/69. Accepted 8/19/69.