Characterization of Nuclear, and Nuclear Matrix-Bound DNA Polymerases of Normal Rat Liver

DNA polymerases in the nuclei and those bound to the nuclear matrices isolated from normal rat liver (at G_0 phase) were characterized. The nuclei from 1 gram tissue contained 0.46 unit of DNA polymerase α (0.05U/mg protein) and 19 units of DNA polymerase β (2.2U/mg), but the nuclear matrices from 1 gram tissue had less than 0.01 unit of DNA polymerase α (2% of the activity in the nuclei) and 0.4 unit of DNA polymerase β (2% of the nuclear activity). In contrast, regenerating rat liver (at S-phase) contained more than ten times higher activity of DNA polymerase α in the nuclei (5.2U/g tissue) and 20% of the activity of this enzyme was bound to nuclear matrices. S-phase nuclei contained almost the same activity of DNA polymerase β (21 units/g tissue) as that in the G_0 nuclei, and 0.5% of the β activity was bound to the nuclear matrices. These findings indicate that no functional replication complex is assembled in the G_0 nuclei and no significant DNA polymerases are bound to the nuclear matrices