Characterization of a New Murine Cellular DNA Polymerase

A new DNA polymerase (peak A) has been identified in the high-speed pellet fraction of two subclones of nonvirus producing Balb/3T3 cells. The activity is associated with a molecule of approximately 70,000 molecular weight and chromatographs in two systems like the mouse type-C viral reverse transcriptase and a similar enzyme from the high-speed pellet fraction of a virus producing Balb/3T3 subclone, S(2)Cl(3). Comparable quantities of peak A are present in both nonvirus infected (A31) and mouse sarcoma virus transformed nonproducer (KA31) subclones. Virus producing cells contain 10-20 times more peak A polymerase activity. A31 and KA31 peak A are comparably inhibited by anti-mouse type C virus reverse transcriptase IgG but to a lesser degree than S(2)Cl(3) peak A or authentic viral reverse transcriptase. They can also be differentiated from the latter two enzymes by template preference studies. KA31 peak A can be distinguished from three other KA31 DNA polymerases (R-DNA polymerase and DNA polymerase N and C), and thus appears to be a new species of cellular DNA polymerase.