Association of an endoribonuclease with the avian myeloblastosis virus deoxyribonucleic acid polymerase.

A ribonuclease degrading only RNA complexed to DNA is found associated with the avian myeloblastosis virus DNA polymerase. A convenient and sensitive assay for the enzyme is degradation of [3H]poly(A) complexed to poly(dT). Using this assay, nuclease and DNA polymerase activities are inseparable by DEAE-Sephadex or phosphocellulose ion exchange chromatography or by glycerol gradient centrifugation. Poly(A) labeled selectively at each end can be used to demonstrate that the nuclease is an endonuclease, and chromatography of the digestion products of poly(A) confirms this result. The oligonucleotide digestion products can be further digested to 5’-AMP by venom phosphodiesterase, indicating that they are terminated by 3’-OH groups.