DNA-binding peptides from rat liver and Novikoff hepatoma cells: quantitative level and possible biochemical differences.

DNA isolated from rat liver by intensive deproteinization with chloroform/isoamyl alcohol and phenol contains low molecular weight peptides in a quantity of about 20 micrograms/mg DNA. These peptides show high specific activity in inhibiting transcription in a reconstituted cell-free system with prokaryotic and eukaryotic RNA polymerase. Their level is markedly decreased in DNA prepared from Novikoff hepatoma cells. Moreover the amino acid analysis and the pattern of analytical separation by high performance liquid chromatography (HPLC) show some biochemical differences between DNA-binding peptides extracted from rat liver and Novikoff hepatoma cells. The possibility that carcinogenesis may involve mechanisms which lead to selective removal of some components of the DNA-binding peptides, is discussed.