In attempt to investigate histone fractions of tumor cells, histone fractions HI H2a, H2b, Iii and H4 were prepared from isolated nuclei of AH-66 hepatoma cells and histone fractions were characterized by amino acid analysis and by poly acrylamide disc gel electrophoresis.
The results obtained were as follows:
1. The five histone fractions found in most tissues were also present in the AH-66 hepatoma cell histones.
2. The yield of whole histon2 was 6.46mg per g of packed cells.
3. The yield of DNA was 11.78mg per g packed cells. Consequently the DNA to histone ratio `vas 1 0.44.
4. Tire relative amounts of five fractions, i. e., HI, H2a, H2b, H3 and H4 were 15. 6d, /00/´ 34. 83,0/0´ 21. 21,0 , 11.76%0 and 16.56/00/, respectively. The data presented in this report show that there is a considerable variation in the relative amounts of histone fractions as compared to those of calf thymus.
5. The electrophoretic mobility of individual histone fractions gave almost similar patterns to those of corresponding fractions of calf thymus.
6. Amino acid ´analysis of the individual histone fractions showed that the over-all compositions were similar but not identical to those of corresponding fractions from calf thymus and other tumor cells.
7. His one fractions HI, 1-12b, H3 and H4 were found to contain detectable amounts of e-N-monomethyl lysine. Usually the methylated derivatives of histidine have been reported in histone HI fraction of Sarcoma 180 ascites tumor cells and Walker 256 carcinosarcoma. However, the methylated histidine residue was not found in all histone fractions from AH-66 hepatoma cells.
8. The evidence was presented that AH-66 hepatoma cells contained five major histone fractions which were homologous to corresponding five fractions of calf thymus.
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