Separable DNA polymerase activities in host liver and Morris hepatomas.

DNA polymerase activities were extracted from the cy toplasm and from nuclei of host liver and Morris hepatoma 7800 and 7777. An improved method of isolating hepatoma nuclei in high yield and in relatively pure form is reported. Three major activities were extracted, one from the cytoplasm and two from the nuclei. The cytoplasmic extract derived from hepatoma 7777 has a higher activity than cytoplasmic extract from hepatoma 7800, and cy toplasmic host liver extract has the lowest activity. Ex traction of nuclei with potassium phosphate yields a polymerase activity that is present in about equal amounts in the three tissues. A second extraction of nuclei with NaCl yields a different kind of activity. This activity is in creased in the hepatomas similar to the cytoplasmic ac tivity. The three activities differ in their elution from diethylaminoethyl cellulose, their primer preference, their reaction to the presence of KC1 in the incubation medium, their ability to incorporate label in the absence of the three unlabeled deoxyribonucleoside triphosphates, and their ability to form an acid-precipitable product with syn thetic polymers as primer. The activity extracted from the nuclei with NaCl differed further from the other two activities in its pH optimum, Mg2+ concentration re