| Summary: | <p>Abstract</p> <p>Background</p> <p>The formation of new infectious human immunodeficiency type 1 virus (HIV-1) mainly relies on the homo-multimerization of the viral structural polyprotein Pr55<sup>Gag </sup>and on the recruitment of host factors. We have previously shown that the double-stranded RNA-binding protein Staufen 1 (Stau1), likely through an interaction between its third double-stranded RNA-binding domain (dsRBD3) and the nucleocapsid (NC) domain of Pr55<sup>Gag</sup>, participates in HIV-1 assembly by influencing Pr55<sup>Gag </sup>multimerization.</p> <p>Results</p> <p>We now report the fine mapping of Stau1/Pr55<sup>Gag </sup>association using co-immunoprecipitation and live cell bioluminescence resonance energy transfer (BRET) assays. On the one hand, our results show that the Stau1-Pr55<sup>Gag </sup>interaction requires the integrity of at least one of the two zinc fingers in the NC domain of Pr55<sup>Gag </sup>but not that of the NC N-terminal basic region. Disruption of both zinc fingers dramatically impeded Pr55<sup>Gag </sup>multimerization and virus particle release. In parallel, we tested several Stau1 deletion mutants for their capacity to influence Pr55<sup>Gag </sup>multimerization using the Pr55<sup>Gag</sup>/Pr55<sup>Gag </sup>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 Pr55<sup>Gag </sup>multimerization and particle release. However, this region is not required for Stau1 interaction with the viral polyprotein Pr55<sup>Gag</sup>.</p> <p>Conclusion</p> <p>These data highlight that Stau1 is a modular protein and that Stau1 influences Pr55<sup>Gag </sup>multimerization via 1) an interaction between its dsRBD3 and Pr55<sup>Gag </sup>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.</p>
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