HIV-1gag-polmRNA localization regulates the site of virion assembly

Abstract

ABSTRACTHIV-1 full-length, unspliced genomic RNAs (gRNAs) serve both as mRNAs encoding the Gag and Gag-Pol capsid proteins as well as the genetic material packaged by Gag into virions that assemble at the plasma membrane (PM). Whether localized Gag synthesis contributes to assembly at the PM is unknown. Here we show that artificially tethering gRNAs or surrogategag-pol mRNAs to non-PM membranes or the actin cytoskeleton can markedly affect Gag’s distribution in the cytoplasm, causing aberrant subcellular sites of assembly and severe reductions to virus particle output. Onlygag-polmRNAs competent for translation were capable of altering Gag’s distribution within the cell, and the activity mapped to twocis-acting RNA regulatory elements; the 5’ packaging signal (Psi) bound by Gag and, unexpectedly, the Rev response element (RRE) that regulates the nuclear export of gRNAs and other intron-retaining viral RNAs. Taken together, our results suggest a model wherein localized translation of gRNAs at the PM helps to compartmentalize Gag-gRNA interactions, thereby promoting efficient genome encapsidation.AUTHOR SUMMARYThe spatial distribution of messenger RNAs (mRNAs) within the cytoplasm can be a crucial determinant of gene expression. Here we provide evidence that a devastating viral pathogen, human immunodeficiency virus type 1 (HIV-1), exploits localized translation to favor the formation of infectious, transmissible virions at the surface of infected cells. Artificially tethering viral mRNAs encoding the Gag and Gag-Pol capsid proteins (gag-polmRNAs) to alternative regions of the cell such as cytoplasmic vesicles or the actin cytoskeletion markedly alters Gag subcellular distribution, perturbs sites of assembly, and reduces virus particle production. These and additional findings suggest a model for HIV-1 assembly wherein localized Gag/Gag-Pol translation coupled to confined interactions between Gag and viral genomes ensures infectious virion production at the right place and the right time. Perturbing HIV-1 mRNA subcellular localization could represent a novel antiviral strategy.