Distinguishing cytomegalovirus, mycoplasma, and cellular DNA polymerases.

Cytomegalovirus-induced DNA polymerase can be distinguished from infected-cell enzymes by activity in 100 mM (NH4)2SO4. Virus polymerase is stimulated to 145% of control, whereas mock-infected cell polymerase is inhibited to 12% of control without added salt. Mycoplasmas induce a DNA polymerase in cell extracts that is stimulated to 130 to 180% by 25 mM (NH4)2SO4. Mycoplasma DNA polymerase may be mistaken for a virus-induced polymerase when virus stocks are contaminated. Identification of virus, cellular, and mycoplasma DNA polymerases in total cell extracts is described using sedimentation rate and effect of inhibitors on DNA polymerase activities.