Reverse transcription in a macromolecular complex of ovine bone marrow: possible involvement in the antigen receptor mediated signal transduction process.
A macromolecular fraction was isolated from ovine bone marrow and designated the active fraction (AF). Two distinct enzymatic activities were detected in the AF: (1) a RNA-dependent RNA polymerase, and (2) a reverse transcriptase. RNA polymerase uses an endogenous RNA molecule of the AF as the template while the product of this RNA polymerase reaction forms the template for the reverse transcriptase. Synthetic reactions are initiated exclusively upon the exposure of the in vitro system to one of the external proteins, selected at random, ovalbumin or insulin. Ovalbumin specific (OS) and insulin specific (IS) AF fractions were prepared. OS-AF binds 14C-ovalbumin and the IS-AF binds 14C-insulin, but not vice versa. Reverse transcription activity of OS-AF is stimulated only upon its exposure to ovalbumin and not to insulin while the reverse is true for the activity associated with IS-AF. Indirect evidence indicates that the enzymes which synthesize nucleic acids are closely associated with the antigen receptor on the B-lymphocyte plasma membrane, the mlgM, and that the antigen binding to its receptor helps in the activation of these enzymes.
Thampan
R V
RV
Department of Biochemistry, School of Life Sciences, University of Hyderabad, India.
D000818:Animals; D001853:Bone Marrow / Q000201:enzymology*; D004247:DNA / Q000096:biosynthesis; D004789:Enzyme Activation / Q000187:drug effects; D005803:Genes, Immunoglobulin; D006041:Goats / Q000276:immunology; D007075:Immunoglobulin M / Q000502:physiology; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology; D046911:Macromolecular Substances; D010047:Ovalbumin / Q000378:metabolism / Q000494:pharmacology; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D012313:RNA / Q000096:biosynthesis / Q000235:genetics; D012324:RNA-Dependent RNA Polymerase / Q000378:metabolism*; D012194:RNA-Directed DNA Polymerase / Q000378:metabolism*; D011947:Receptors, Antigen, B-Cell / Q000502:physiology*; D012756:Sheep / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013045:Species Specificity; D013698:Templates, Genetic
D007075:Immunoglobulin M; D007328:Insulin; D046911:Macromolecular Substances; D011947:Receptors, Antigen, B-Cell; D012313:RNA; D010047:Ovalbumin; D004247:DNA; D011505:Protein-Tyrosine Kinases; D012324:RNA-Dependent RNA Polymerase; D012194:RNA-Directed DNA Polymerase