ENZYMES OF DNA-SYNTHESIS IN ISOLATED-NUCLEI OF SWINE AORTA

Enzymes of DNA synthesis, thymidine kinase (ATP-thymidine-5''-phosphotransferase, EC 2.7.1.21), DNA polymerase (EC 2.7.7.7) and nuclease activities were investigated in isolated purified nuclei of swine aorta. Thymidine kinase which is detectable in these nuclei can be stimulated by the addition of phospholipase C. DNA polymerase activity of isolated nuclei is strongly dependent on addition of an exogenous template; the preferred template is activated DNA. The activity in the absence of an added template is very low except when labeled dCTP is used as the precursor. This incorporation of labeled dCTP does not require the addition of the other 3 triphosphates, and under these conditions, dCTP seems to be incorporated into what may be a homopolymer. As with other tissues, solubilized preparations of aortic nuclei have 2 DNA polymerase activities which also prefer activated DNA template. There is no detectable endonuclease in aortic nuclei.