Phosphatidylinositol-dependent activation of DNA polymerase alpha

DNA polymerase alpha was activated invitro by cAMP-independent, phospholipid-dependent, protein kinase catalytic subunit. Of the phospholipids examined, phosphatidylinositol showed the greatest potential for interaction with protein kinase and ATP to activate DNA polymerase alpha invitro. DNA polymerase alpha was directly activated by phosphorylated phosphatidylinositol in the absence of protein kinase and ATP. Activation of DNA polymerase alpha as a function of phosphorylation was demonstrated using ³²P-ATP as the phosphate donor. Invitro treatment of the enzyme with phosphatidylinositol produced Linweaver-Burk plots showing noncompetitive kinetics of enzyme activation, suggesting that activation occurs prior to binding of the enzyme to DNA template/primer. These data indicate that DNA polymerase alpha may be activated invitro in the presence of protein kinase, ATP, and phosphatidylinositol, and suggest that phosphorylation of the enzyme may constitute an intracellular mechanism of enzyme activation.