title: RNase H and RNA-directed DNA polymerase: associated enzymatic activities of murine mammary tumor virus.
abstract: The RNA-directed DNA polymerase of murine mammary tumor virus, a type B RNA tumor virus, was purified sequentially through DEAE-cellulose, phosphocellulose (step gradient), and phosphocellulose (linear salt gradient) chromatography followed by glycerol sedimentation centrifugation. During all stages of purification, coincident peaks of RNA-directed DNA polymerase activity, templated by polyribocytidylate-oligodeoxyguanidylate, and RNase H digestion of [3H]polyriboadenylate-polydeoxythymidylate were observed, and both enzymatic activities displayed a cation preference for magnesium. Under conditions that removed adventitiously associated nucleases, RNase H activity was found to co-purify with polymerase. The specificity of this nuclease was assayed with various prepared substrates, which indicated that the polymerase-associated RNase H activity was directed only against the RNA strand of an RNA-DNA hybrid. It is highly probable that RNase H (RNA-DNA hybrid: ribonucleotide-hydrolase, EC 3.1.4..34) and RNA-directed DNA polymerase of type B viruses are associated enzymatic activities analogous to those observed for avian and mammalian type C RNA tumor viruses.
mesh_terms: D008324:Mammary Tumor Virus, Mouse / Q000201:enzymology*; D008970:Molecular Weight; D012194:RNA-Directed DNA Polymerase / Q000302:isolation & purification / Q000378:metabolism; D012260:Ribonucleases / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D012194:RNA-Directed DNA Polymerase; D012260:Ribonucleases