Abstract
The purification and characterization of the DNA polymerase from human breast cancer particles were previously reported. Its preference for certain synthetic templates and its ability to use a viral RNA to fashion a faithful DNA transcript identify it as a reverse transcriptase similar to that found in the mouse mammary tumor virus and in the Mason-Pfizer monkey virus (MPMV). The human breast cancer enzyme crossreacts immunologically with the reverse transcriptase of MPMV. The crossreactivity was shown by inhibition of enzyme activity and by complex formation between purified enzyme and isolated Ig[immunoglobulin]G against MPMV polymerase. No such interactions were observed with other oncornavirus reverse transcriptases of avian, murine, feline or simian origin. The IgG failed to neutralize the reverse transcriptases from human mesenchymal neoplasias (leukemias and lymphomas) or the activities of normal cellular DNA polymerases (.alpha., .beta., .gamma.).