ABSTRACT Human immunodeficiency virus type 1 (HIV-1) uses tRNA \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(_{3}^{Lys}\) \end{document} as a primer for reverse transcription and, during viral assembly, this tRNA is selectively packaged into the virus along with the other major tRNA Lys , tRNA \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(_{1,2}^{Lys}\) \end{document} . Increasing the cytoplasmic concentration of tRNA \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(_{3}^{Lys}\) \end{document} through transfection of cells with a plasmid containing both HIV-1 proviral DNA and a tRNA \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(_{3}^{Lys}\) \end{document} gene results in a greater incorporation of tRNA \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(_{3}^{Lys}\) \end{document} into virions, which is accompanied by increased annealing of tRNA \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(_{3}^{Lys}\) \end{document} to the viral genome and increased infectivity of the viral population. Increased viral tRNA \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(_{3}^{Lys}\) \end{document} is accompanied by decreased viral tRNA \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(_{1,2}^{Lys}\) \end{document} , with the total tRNA Lys /virion and the GagPol/Gag ratios remaining unchanged. Viral tRNA Lys can be doubled, with increases in both tRNA \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(_{3}^{Lys}\) \end{document} and tRNA \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(_{1,2}^{Lys}\) \end{document} concentrations, by overexpressing lysyl tRNA synthetase. This also results in increased tRNA \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(_{3}^{Lys}\) \end{document} annealing to the viral RNA and increased viral infectivity but, again, no change in the GagPol/Gag ratio was observed. This result indicates that GagPol, whose interaction is required during packaging, is not a limiting factor during tRNA Lys incorporation into HIV-1, whereas LysRS is.