Incorporation of genome-bound cellular proteins into HIV-1 particles regulates viral infection
The initial steps of the human immunodeficiency virus type 1 (HIV-1) lifecycle are regulated by cellular RNA-binding proteins, but only a few have been identified. Here, we developed in virion RNA interactome capture (ivRIC) to comprehensively profile the direct protein interactors of the HIV-1 genomic (g)RNA inside the viral particles. We identified 104 cellular RNA-binding proteins in virions (ivRBPs), many of which are nuclear. We determined the interactome of the viral RBP Rev and discovered that nuclear ivRBPs may associate gRNA in the nucleus and continue bound after the genesis of the viral particles. We also observed that ivRBPs are not incorporated into viral particles based on their  abundance, but likely through selective mechanisms. Moreover, we show that the ivRBPs PURA and its homologue PURB control HIV-1 particle infectivity and engage with several viral proteins and key elements within HIV-1 gRNA, showcasing the importance of ivRBPs for HIV-1 infection.