Abstract
The effects of salt treatment of isolated nuclei on the nature of DNA synthesis and on the solubilization of DNA polymerase a have been investigated. Treatment with 0.2 M KCl resulted in a deficiency in the function to join Okazaki fragments, whereas the synthesis of these fragments was little affected. No DNA synthesis was observed in 0.3 M KO-treated nuclei. DNA synthesis in 0.2 M KCl-treated nuclei required ATP, Mg2+ and four deoxy- ribonucleoside triphosphates, and was markedly inhibited by arabinofuranosyl-cytosine triphosphate and aphidicolin, but not by 2', 3'-dideoxythymidine triphosphate. This suggests that the DNA synthesis is the replicative-type, catalyzed by DNA polymerase a. DNA polymerase a in 0.3 M Kcl-nuclear extract was detected as two active forms distinct in their binding affinities for DNA. In 0.2 M KCl-treated nuclei, only one active form with high binding affinity was retained, indicating that this form is responsible for the synthesis of Okazaki fragments.
