REVERSE-TRANSCRIPTASE OF HUMAN-IMMUNODEFICIENCY-VIRUS CAN USE EITHER HUMAN TRANSFER RNA(3)LYS OR ESCHERICHIA-COLI TRANSFER RNA(2)GLN AS A PRIMER IN AN INVITRO PRIMER-UTILIZATION ASSAY

Although the reverse transcriptase (RT) of human immunodeficiency virus (HIV) uses human tRNA3Lys as a primer of viral genome DNA synthesis in vivo, HIV RT binds Escherichia coli glutamine tRNA and in vitro-made human lysine tRNA with nearly equivalent affinities. We show that HIV RT can use either tRNA3Lys or tRNA2Gln as a primer for DNA synthesis in vitro without the addition of any other host or viral proteins. E. coli tRNA2Gln can serve as a primer for HIV RT if a primer-binding site sequence complementary to the 3' end of tRNA2Gln is at the 3' end of the template. With this reduced template, the specificity of binding the proper tRNA is due to base-pairing between a bound tRNA to the primer-binding site of the viral RNA template rather than sequence-specific recognition of tRNA3Lys by RT. If an 8-nucleotide viral sequence 3' to the primer-binding site is included in the template, then addition of Zn2+ or Co2+ is required for tRNA3Lys-primed synthesis, and tRNA2Gln now fails to prime synthesis. The latter result implies that a template sequence adjacent to the primer-binding site and containing 6 nucleotides complementary to the anticodon loop of human tRNA3Lys plays an active role in tRNA discrimination.