Intracellular localization and metabolism of DNA polymerase alpha in human cells visualized with monoclonal antibody

Indirect immunofluorescence microscopy with monoclonal antibody against DNA polymerase alpha revealed the intranuclear localization of DNA polymerase alpha in G1, S, and G2 phases of transformed human cells, and dispersed cytoplasmic distribution during mitosis. In the quiescent, G0 phase of normal human skin fibroblasts or lymphocytes, the alpha-enzyme was barely detectable by either immunofluorescence or enzyme activity. By exposing cells to proliferation stimuli, however, DNA polymerase alpha appeared in the nuclei just prior to onset of DNA synthesis, increased rapidly during S phase, reached the maximum level at late S and G2 phases, and was then redistributed to the daughter cells through mitosis. It was also found that the increase in the amount of DNA polymerase alpha by proliferation stimuli was not affected by inhibition of DNA synthesis with aphidicolin or hydroxyurea.