DNA REPLICATION AND DEGRADATION IN MAMMALIAN TISSUE .I. CHANGES IN DNA POLYMERASE AND NUCLEASE DURING RAT LIVER REGENERATION

The incorporation of [3H]thymidine into rat liver DNA, DNA polymerase activity, and deoxyribonuclease activity have been compared at various times following partial hepatectomy of the rat. 1. 1. DNA polymerase activity increases when [3H]thymidine incorporation in vivo increased and remained elevated for at least 60 h following partial hepatectomy, despite waves of DNA synthesis. Fluctuations in nuclease activity were directly opposite to the peaks of [3H]thymidine incorporation at different times during regeneration. It is suggested that deoxyribonuclease plays an important role in the control of DNA synthesis. 2. 2. Rat liver polymerase had a preference for native DNA primer whereas deoxyribonuclease in the same preparation acted preferentially on denatured DNA. It is suggested that the apparent difference in polymerase primer preference is due to nuclease activity associated with the pH 5.0 protein fraction. © 1969.