Covalent Linkage Between Ribonucleic Acid Primer and Deoxyribonucleic Acid Product of the Avian Myeloblastosis Virus Deoxyribonucleic Acid Polymerase

Abstract

Initiation of deoxyribonucleic acid (DNA) synthesis by the avian myeloblastosis virus DNA polymerase was previously suggested to involve a ribonucleic acid (RNA) primer, the initial product being a DNA molecule joined by a phosphodiester bond to the RNA primer. The existence and nature of such an RNA-DNA joint was investigated by assaying for transfer of a 32 P atom from an α- 32 P-deoxyribonucleotide to a 2′(3′)-ribonucleotide after alkaline hydrolysis of the polymerase product. Such a transfer was observed, but only from α- 32 P-deoxyadenosine triphosphate and only to 2′(3′)-adenosine monophosphate. This same transfer was observed in both the endogenous DNA polymerase reaction of purified virions and the reconstructed reaction of purified DNA polymerase plus purified 60 to 70 S viral RNA. These results indicate a high level of specificity for the initiation process and support the idea of a low-molecular-weight initiator RNA as part of the 60 to 70 S RNA complex.