The infidelity of avian myeloblastosis virus deoxyribonucleic acid polymerase in polynucleotide replication.

We have studied the accuracy of DNA synthesis in vitro by purified avian myeloblastosis virus (AMV) DNA polymerase (“reverse transcriptase”) using synthetic polynucleotide templates. The enzyme catalyzes the incorporation of an exceptionally large number of incorrectly paired bases when copying ribopolynucleotide and deoxyribopolynucleotide templates. The frequency of error is approximately 1 in 600 when copying homopolymer templates and 1 in 6000 when copying alternating copolymer templates. The product of the reaction, using a template of polyriboadenylic acid of 2500 nucleotides long hybridized to an initiator of oligodeoxythymidylate of 12 to 18 nucleotides long was analyzed by telocity sedimentation and equilibrium density gradient centrifugation. The results indicate that: (a) the entire length of the given template is copied; (b) the incorrectly base-paired nucleotides are an integral part of the polynucleotide product; and (c) these errors are randomly distributed. Polyacrylamide gel electrophoretic analysis of the purified polymerase showed two subunits, Q and /3. The incorporation of the correct and incorrect nucleotides catalyzed by the active CY subunit appears to be not influenced by the inactive p subunit. The purified polymerase has no detectable exoor endodeoxyribonuclease activity. AMV DNA polymerase exhibits identical requirements for the incorporation of the correct and incorrect nucleotides. The error rate is not a function of the number of initiator termini, Mg*+ concentration, time of incubation, or the amount of enzyme. The error rate is, however, dependent on the type of the template and on the ratio of correct to incorrect nucleotides in the reaction mixture. If this DNA polymerase from avian myeloblastosis virus makes similar errors in uiuo this enzyme may be mutagenic.