Partial purification and characterization of DNA polymerases from a Rous sarcoma virus-transformed rat cell line

A new DNA polymerase was partially purified from cell-free extracts of a continuous rat cell-line (XC). The XC cells had been transformed by the Prague strain of Rous sarcoma virus but did not produce infectious virus. The molecular weight of the DNA polymerase is 70,000, as estimated by glycerol gradient centrifugation and by Sephadex gel filtration. This enzyme can be distinguished from the other cellular DNA polymerases by its elution pattern on DNA-cellulose column chromatography, its molecular weight, and its primer-template specificity. The enzyme has some characteristics of the murine leukemia virus reverse transcriptase. It is partially inhibited by immunoglobulin G purified from rabbit antiserum prepared against Rauscher leukemia virus reverse transcriptase, but is not inhibited by IgG from rat antiserum prepared against avian myeloblastosis virus reverse transcriptase. However, the XC cell enzyme can be distinguished from the murine leukemia virus reverse transcriptase by its inefficiency in copying an oligo(dG)12-poly(rC)primer-template.