Effect of poly(ADP-ribose) formation on DNA synthesis and DNA fragmentation in nuclei of rat liver and rat ascites hepatoma AH-130 cells

To elucidate the role of poly(ADP-Rib) in the nucleus, DNA synthesis and DNA fragmentation were studied in isolated nuclei of rat liver and rat ascites hepatoma AH-130 cells. Liver and hepatoma cell nuclei formed the same amount of poly(ADP-Rib) per mg of nuclear DNA from NAD. Preincubation of liver nuclei with NAD repressed DNA polymerase activity to 30% of that of the control, but preincubation of hepatoma cell nuclei with NAD did not affect DNA polymerase activity. It was also found that incubation of liver nuclei with NAD prevented the fragmentation of nuclear DNA which occurred without NAD. Incubation of hepatoma cell nuclei with or without NAD did not result in fragmentation of DNA. The role of endonuclease in primer formation for DNA synthesis is discussed.