12] Endogenous RNA-directed DNA polymerase activity in virions of RNA tumor viruses and in a fraction from normal chicken cells

Abstract

Publisher Summary This chapter describes methods for assaying endogenous RNA-directed DNA polymerase activity in virions of RNA tumor viruses and in a fraction from normal chicken cells. The endogenous DNA polymerase activities have requirements similar to those of the usual exogenous DNA-directed DNA polymerase activity—that is, requirements for 4-de-oxyribonucleoside triphosphates, a divalent cation such as Mg 2+ or Mn 2+ , and a template-primer. The special feature of the assay of the endogenous RNA-directed DNA polymerase activities is that the DNA polymerase and template-primer are present as a specific complex in a virus particle or in a fraction isolated from uninfected chicken embryos. Both of these endogenous DNA polymerase activities are sensitive to ribonuclease, resistant to deoxyribonuclease, and partially resistant to actinomycin D. The initial product of both these endogenous DNA polymerase activities is an RNA-DNA hybrid, and the DNA product hybridizes with the template RNA's.