Identification of a higher molecular weight DNA polymerase α catalytic polypeptide in monkey cells by monoclonal antibody

A monoclonal antibody against purified calf DNA polymerase α (deoxynucleosidetriphosphate:DNA deoxy-nucleotidyltransferase, EC 2.7.7.7) was used to immunoprecipitate proteins from a crude soluble extract of growing monkey BSC-1 cells. Immunoprecipitates contained familiar DNA polymerase α catalytic polypeptides of M(r)S ≃ 115,000 and 70,000 and also a M(r) 40,000 catalytic polypeptide; the major component in the immunoprecipitates, however, was a polypeptide M(r) ≃ 190,000 not previously identified as a DNA polymerase. This protein was capable of DNA polymerase activity after electroelution from NaDodSO₄/polyacrylamide gels and renaturation. The highly purified enzyme so obtained was active with poly(dT)·oligo(rA) as template·primer, resistant to dideoxy TTP (ddTTP), and inhibited by aphidicolin and butylphenyldeoxyguanosine 5'-triphosphate, thus identifying it as a DNA polymerase α. The results indicate that a polypeptide of M(r) ≃ 190,000 is an abundant component among DNA polymerase α catalytic polypeptides in growing monkey cells.