A multiprotein form of DNA polymerase α from HeLa cells. Resolution of its associated catalytic activities

The majority of the DNA polymerase α activity in HeLa cells has been isolated and purified as a multiprotein M(r) 640,000 form. The multiprotein form of DNA polymerase α corresponds to DNA polymerase α₂ that was previously reported by us (Lamothe, P., Baril, B., Chi, A., Lee, L., and Baril, E. (1981) Proc. Natl. Acad. Sci. U.S.A. 78, 4723-4727). The highly purified DNA polymerase α₂ has in addition to DNA polymerase α-associated DNAse, primase, and diadenosine 5',5-P¹,P⁴-tetraphosphate (Ap₄A) binding activities and accessory primer recognition proteins C₁ and C₂. The DNA polymerase α and associated activities increase coordinately during the G1/S-phase transition of the cell cycle. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of the electrophoretically homogeneous DNA polymerase α shows that it is composed of at least eight polypeptides in the molecular weight range of 180,000-15,000. Hydrophobic chromatography on butyl-agarose resolves the DNAse and Ap₄A-binding protein from a complex of DNA polymerase α, primase, and the primer recognition proteins C₁ and C₂. Hydrophobic chromatography of the latter complex on phenyl-Sepharose resolves the C1 protein from a DNA polymerase α-C₂ protein-primase complex. Phosphocellulose chromatography of the DNA polymerase-primase-C₂ protein complex resolves the C₂ protein from a complex of DNA polymerase α-primase.