| Like all retroviruses, the human immunodeficiency virus type 1 (HIV-1) replicates in cells by reverse transcribing its single-stranded RNA genome into double-stranded DNA, which is integrated into cellular DNA. HIV-1 begins reverse transcription by co-opting a specific cellular tRNA, tRNALys3, which is annealed onto the viral RNA and serves as a primer. tRNALys3 is packaged into HIV-1 virions during virus assembly through a specific interaction with Gag, GagPol, and lysyl-tRNA synthetase, the major tRNALys-interacting factor in cells. Particle assembly is orchestrated by Gag, which concentrates necessary cellular and viral components at the plasma membrane. Gag contains the matrix (MA), capsid (CA), spacer 1, nucleocapsid (NC), spacer 2, and p6 domains and interacts with LysRS via CA, viral RNA and tRNALys3 via primarily NC, and the plasma membrane via MA. However, each of these domains is multifunctional and binds many other factors during assembly. In this work, I examine how Gag facilitates tRNA primer annealing in vitro and show that MA interacts with RNA and blocks Gag's ability to refold nucleic acids. I then investigate Gag's chaperone activity by studying its zinc fingers, two highly conserved motifs responsible for its ability to weakly destabilize RNA secondary structure. Finally, I show that the structure of 5' untranslated region of the HIV-1 genome mimics the secondary structure of its primer tRNALys3 to enhance the efficiency of tRNA annealing. |
