Description:
<jats:p>DNA polymerases have been isolated from muscle and melanoma tissues of <jats:italic>Xiphophorus</jats:italic>, which are similar to retroviral RNA‐dependent DNA polymerases as they prefer RNA to DNA templates. They appear to associate with submicroscopic structures which exhibit a density of about 1.13 g/ml after sucrose‐density‐gradient centrifugation. The RNA‐dependent‐DNA‐polymerase‐like enzymes could be separated from the DNA‐dependent DNA polymerases by DEAE‐cellulose chromatography. Further purification on phosphocellulose revealed that the muscle enzyme eluted at the void volume and at about 0.6 M KCl, whereas most of the melanoma enzyme eluted at 0.1 M KCl.</jats:p><jats:p>Comparison of the template primer specificities of the muscle and melanoma enzymes with those of known DNA polymerases showed obvious similarities to the RNA‐dependent DNA polymerase isolated from Rous sarcoma virus.</jats:p>