N. Beerens et B. Berkhout, In vitro studies on tRNA annealing and reverse transcription with mutant HIV-1 RNA templates, J BIOL CHEM, 275(20), 2000, pp. 15474-15481
The human immunodeficiency virus type 1 (HIV-1) RNA genome encodes a semist
able stem-loop structure, the US-PBS hairpin, which occludes part of the tR
NA primer binding site (PBS). In previous studies, we demonstrated that mut
ations that alter the stability of the U5-PBS hairpin inhibit virus replica
tion. A reverse transcription defect was measured in assays with the virion
-extracted RNA-tRNA complexes. We now extend these studies with in vitro sy
nthesized wild-type and mutant RNA templates that were tested in primer ann
ealing and reverse transcription assays. The effect of annealing temperatur
e and the presence of the viral nucleocapsid protein on reverse transcripti
on was analyzed for the templates with a stabilized or destabilized U5-PBS
hairpin, and in reactions initiated by tRNA or DNA primers. The results of
this in vitro assay are consistent with the in vivo findings, in that both
tRNA annealing and initiation of reverse transcription are sensitive to sta
ble template RNA structure. Reverse transcription initiated by a DNA primer
is less hindered by secondary structure in the RNA template than tRNA prim
ed reactions. The inhibitory effect of template structure on tRNA-primed re
verse transcription is more pronounced in this in vitro assay compared with
the in vivo material, indicating that the heat-annealed RNA-tRNA complex d
iffers from the virion-extracted viral RNA-tRNA complex.