SV40 T-ANTIGEN BINDS DIRECTLY TO THE LARGE SUBUNIT OF PURIFIED DNA POLYMERASE-ALPHA

Purified SV40 large T antigen and purified DNA polymerase α - primase form a complex detectable by ELISA and by a modified immunoblotting technique. The interaction is specific for the large catalytic subunit of polymerase α. The amino terminal 83 amino acids of T antigen are both necessary and sufficient for binding to the polymerase. However, antibody epitopes located in the carboxy terminal ATPase domain of T antigen are masked in the polymerase-T antigen complex, and complex formation is inhibited by an antibody directed against the carboxy terminus of T antigen, suggesting that this region of T antigen, though not required for binding, is in close proximity to the bound polymerase. The affinity of human DNA polymerase α for T antigen is ~10-fold greater than that of polymerase α from calf thymus, consistent with the interpretation that polymerase α is at least in part responsible for the primate-specific replication of SV40 DNA in vivo and in vitro. The results suggest that specific protein-protein interaction between DNA polymerase α and T antigen plays an important role in viral DNA replication.