Interaction of DNA polymerases with phospholipids.

Effects of various phospholipids on the in vitro reactions of eukaryotic DNA polymerases alpha, beta and gamma were tested systematically. When phospholipids were added directly to the reaction mixture, neither stimulation nor inhibition was produced. However, when phospholipids were preincubated with enzymes in the absence of template-primer, some of them showed strong inhibition. Cardiolipin strongly inhibited the reactions of all three DNA polymerases and also of terminal deoxynucleotidyl transferase. Phosphatidylinositol selectively inhibited the reaction of DNA polymerase gamma. Phosphatidic acid moderately inhibited DNA polymerase alpha and strongly inhibited DNA polymerase gamma. The inhibition of DNA polymerase gamma by cardiolipin was nearly competitive with template-primer. Since the inhibition was reversed by the addition of 0.05% Triton-X 100 during preincubation, the phospholipid might interact with enzyme protein at the hydrophobic region in competition with template-primer. These results suggest a possible involvement of phospholipids in DNA replication in mitochondria and in nucleus through interaction with DNA polymerase.