Changes of mitochondrial DNA polymerase-gamma activity in synchronized mouse cell cultures.

Following synchronization by a double hydroxyurea block, mouse cell cultures exhibited a period of accelerated precursor incorporation into mitochondrial DNA during the late nuclear S phase. Peak activity of mitochondrial DNA polymerase-gamma occurred concurrent to the interval of accelerated organelle DNA synthesis. Mixing experiments suggested that the variations in mitochondrial DNA polymerase activity during the cell cycle were not due to free inhibitors in the enzyme preparations examined.