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

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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.