Avian retrovirus RNA-directed DNA synthesis by purified reverse transcriptase. Covalent linkage of RNA to plus strand DNA

Abstract

Summary DNA with the same polarity as its viral RNA template was synthesized in reconstructed reactions containing highly purified avian myeloblastosis virus DNA polymerase and 35S RNA template-·tRNA trp primer. By performing radioisotope transfer experiments with plus strand DNA isolated from synthetic reactions containing one of the four α-[ 32 P] deoxyribonucleoside triphosphates, it was determined that RNA is covalently linked to the 5′ termini of plus strand DNA. While all 16 possible rNMP-dNMP linkages were detected, 50% of all transfers were to 2′(3′)-AMP. We conclude that 35S RNA·tRNA trp template·primer-directed synthesis of plus strand DNA is initiated with RNA primer(s). The most probable origin of the primer(s) is viral RNase H-generated fragments of the viral RNA template.