Resistance of Chinese hamster ovary cell chromatin to endonuclease digestion. I. Reversal by cAMP

A portion of the DNA within intact nuclei of a spontaneously transformed Chinese hamster ovary cell line (CHO-Kl) is relatively resistant to digestion by pancreatic deoxyribonuclease, as compared to nuclei from primary cultures of Chinese hamster ovary fibroblasts. Treatment of CHO-Kl cells with derivatives of 3',5' cyclic AMP (cAMP) under conditions which effect the reverse transformation (RT) of these cells, results in restoration of the increased sensitivity of their DNA to hydrolysis by pancreatic deoxyribonuclease, to the level characteristic of an untransformed, morphologically normal Chinese hamster fibroblast cell line. Dibutyryl (db-)cAMP and 8-bromo-cAMP (Br-cAMP) yielded similar results. The cAMP derivatives employed had no effect on the normal fibroblasts.