The host protein Staufen1 interacts with the Pr55Gag zinc fingers and regulates HIV-1 assembly via its N-terminus

We now report the fine mapping of Stau1/Pr55Gag association using co-immunoprecipitation and live cell bioluminescence resonance energy transfer (BRET) assays. On the one hand, our results show that the Stau1-Pr55Gag interaction requires the integrity of at least one of the two zinc fingers in the NC domain of Pr55Gag but not that of the NC N-terminal basic region. Disruption of both zinc fingers dramatically impeded Pr55Gag multimerization and virus particle release. In parallel, we tested several Stau1 deletion mutants for their capacity to influence Pr55Gag multimerization using the Pr55Gag/Pr55Gag BRET assay in live cells. Our results revealed that a molecular determinant of 12 amino acids at the N-terminal end of Stau1 is necessary to increase Pr55Gag multimerization and particle release. However, this region is not required for Stau1 interaction with the viral polyprotein Pr55Gag.These data highlight that Stau1 is a modular protein and that Stau1 influences Pr55Gag multimerization via 1) an interaction between its dsRBD3 and Pr55Gag zinc fingers and 2) a regulatory domain within the N-terminus that could recruit host machineries that are critical for the completion of new HIV-1 capsids.Human immunodeficiency type 1 (HIV-1) assembly consists in the formation of new viral particles which is the result of the radial multimerization of approximately 1,400 to 5,000 copies of the viral polyprotein Pr55Gag (also named Gag) according to their quantification in mature or immature particles, respectively [1-3]. Pr55Gag is thought to contain most of the determinants required for viral assembly since the expression of Pr55Gag alone leads to the formation and release of virus-like particles (VLPs), structurally not really distinguishable from immature HIV-1 [4-6]. Pr55Gag is a modular protein that contains 6 domains: matrix (MA), capsid (CA), nucleocapsid (NC), p6 and two spacer peptides, p2 and p1. Each of these domains plays specific roles during HIV-1 life cycle. During