A Single Subunit from Avian Myeloblastosis Virus with Both RNA-Directed DNA Polymerase and Ribonuclease H Activity

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 70; no. 1; pp. 230 - 234
• Main Authors: Grandgenett, Duane P., Gerard, Gary F., Green, Maurice
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 01.01.1973; National Acad Sciences
• Subjects: Avian Leukosis Virus - enzymology; Biological Sciences: Biochemistry; Carbon Isotopes; Centrifugation; Centrifugation, Density Gradient; Chromatography, DEAE-Cellulose; DNA; DNA - metabolism; DNA, Viral - biosynthesis; Electrophoresis; Electrophoresis, Polyacrylamide Gel; Enzymes; Epitopes; Gels; Hybridity; Immunoassay; Molecular Weight; Nucleic Acid Hybridization; Polynucleotides - metabolism; Potassium phosphates; Ribonucleases - isolation & purification; Ribonucleases - metabolism; RNA; RNA, Viral - metabolism; RNA-Directed DNA Polymerase - isolation & purification; RNA-Directed DNA Polymerase - metabolism; Templates, Genetic; Thymus Gland - analysis; Viruses
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.70.1.230

Two structurally distinct forms of RNA-directed DNA polymerase from avian myeloblastosis virus were resolved by chromatography on phosphocellulose and purified. In addition to RNA-directed DNA polymerase activity, both enzymes had ribonuclease H (RNase H) activity, which degraded the RNA moiety of RNA· DNA hybrids. As determined by sodium dodecyl sulfate-polyacrylamide disc-gel electrophoresis, one form had two subunits, alpha (α ) and beta (β ), with molecular weights of 65,000 and 105,000, respectively. The other had a single subunit, α , with a molecular weight of 65,000. The sedimentation coefficients of α β and α , determined by glycerol gradient centrifugation in 0.35 M KCl, were 7.8 S and 5.2 S, respectively. Both enzymes had similar antigenic determinants and could not be distinguished by a differential response to several different RNA and DNA templates. We suggest that α , which contains both RNA-directed DNA polymerase and RNase H activity, is derived by dissociation of α β ; the function of the β subunit is unknown.