INITIATION OF (-) STRAND DNA-SYNTHESIS FROM TRNA(3)(LYS) ON LENTIVIRAL RNAS - IMPLICATIONS OF SPECIFIC HIV-1 RNA-TRNA(3)(LYS) INTERACTIONS INHIBITING PRIMER UTILIZATION BY RETROVIRAL REVERSE TRANSCRIPTASES

Initiation of minus (-) strand DNA synthesis was examined on templates containing R, U5, and primer-binding site regions of the human immuno deficiency virus type 1 (HIV-1), feline immunodeficiency virus (FIV), and equine infectious anemia virus (EIAV) genomic RNA. DNA synthesis w as initiated from (i) an oligoribonucleotide complementary to the prim er-binding sites, (ii) synthetic tRNA(3)(Lys), and (iii) natural tRNA( 3)(Lys), by the reverse transcriptases of HIV-1, FIV, EIAV, simian imm unodeficiency virus, HIV type 2 (HIV-2), Moloney murine leukemia virus , and avian myeloblastosis virus. All enzymes used an oligonucleotide on wild-type HIV-1 RNA, whereas only a limited number initiated (-) st rand DNA synthesis from either tRNA(3)(Lys). In contrast, all enzymes supported efficient tRNA(3)(Lys)-primed (-) strand DNA synthesis on th e genomes of FIV and EIAV. This may be in part attributable to the obs ervation that the U5-inverted repeat stem-loop of the EIAV and FIV gen omes lacks an A-rich loop shown with HIV-1 to interact with the U-rich tRNA anticodon loop. Deletion of this loop in HIV-1 RNA, or disruptin g a critical loop-loop complex by tRNA(3)(Lys) extended by 9 nt, resto red synthesis of HIV-1 (-) strand DNA from primer tRNA(3)(Lys) by all enzymes, Thus, divergent evolution of lentiviruses may have resulted i n different mechanisms to use the same host tRNA for initiation of rev erse transcription.