抄録
In rapidly proliferating Ehrlich ascites tumor cells, DNA polymerase activity has been found which utilizes poly(dC) as a template without added primer. The DNA polymerase responsible for this activity and its stimulating factor were partially purified as reported previously (26). To obtain information on the role of this novel activity in DNA replication, subcellular location and developmental change were studied. The DNA polymerase activity in a crude extract prepared from Ehrlich ascites cells that utilizes single-stranded DNA was characterized by mixing it with purified DNA polymerase and by trypsin digestion. We thus obtained evidence that the activity in crude extract was the same as that of the purified enzyme. The activity in a subcellular fraction, prepared by the procedure using cytochalasin B induced enucleation, was determined. More than 98 % of the activity was found in the karyoplast. We then measured the levels of activity in the spleen and in cardiac muscle, both of which show the characteristic pattern of cellular proliferation during postnatal development. In both tissues, the levels of activity were correlated positively with the rate of DNA synthesis. These results suggest that this novel DNA polymerase activity participates in DNA replication.
