CHARACTERIZATION OF HUMAN DNA POLYMERASE-DELTA AND ITS IMMUNOCHEMICAL RELATIONSHIPS WITH DNA POLYMERASE-ALPHA AND POLYMERASE-EPSILON

DNA polymerase-delta was purified from human placenta and its polymerase catalytic subunit identified as a 125-kDa polypeptide by activity staining. This 125-kDa form of DNA polymerase-delta resembles that reported from calf thymus (Lee, M. Y. W. T., Tan, C.-K., Downey, K. M., and So, A. G. (1984) biochemistry 23, 1906-1913) and differs in molecular properties from a previously described form isolated from human placenta (Lee, M. Y. W. T., and Toomey, N. L. (1987) Biochemistry 26, 1076-1085) and now referred to as DNA polymerase-epsilon. The properties of DNA polymerase-delta were further investigated to determine its relationships with DNA polymerase-epsilon. The two enzymes differed in their response to proliferating cell nuclear antigen. Monoclonal antibodies against DNA polymerase-delta were raised and used to examine its immunochemical relationships with DNA polymerase-alpha and epsilon. These studies provided evidence that all three proteins are structurally distinct but share a common epitope(s). Immunofluorescence microscopy indicates that DNA polymerase-delta and possibly also DNA polymerase-epsilon are localized to the nucleus.