The initial RNA molecule that results from proviral DNA transcription is differentially processed into multiply spliced transcripts that encode Rev and other early-stage viral proteins, as well as partly spliced and unspliced transcripts that encode viral structural and enzymatic proteins and provide genomic RNA for encapsidation. The HIV-1 protein Rev (regulator of expression of the virion) is an RNA-binding protein essential for the production of mature viral particles ( 1, 2) (reviewed in references 3, 4, and 5). These findings shed light on the molecular basis of Rev recognition by Impβ and highlight an atypical binding behavior that distinguishes Rev from canonical cellular Impβ cargos. Cross-linking mass spectrometry and compensatory mutagenesis data combined with molecular docking simulations suggest a structural model in which one Rev monomer binds to the C-terminal half of Impβ with Rev helix α2 roughly parallel to the HEAT-repeat superhelical axis, whereas the other monomer binds to the N-terminal half. Peptide scanning data and charge-reversal mutations identify the N-terminal tip of Rev helix α2 within Rev’s arginine-rich motif (ARM) as a primary Impβ-binding epitope. We show that Impβ binds two Rev monomers through independent binding sites, in contrast to the 1:1 binding stoichiometry observed for most Impβ cargos. Here, we report biochemical, mutational, and biophysical studies of the Impβ/Rev complex. Rev is imported into the nucleus by the host protein importin β (Impβ), but how Rev associates with Impβ is poorly understood. HIV-1 Rev mediates the nuclear export of intron-containing viral RNA transcripts and is essential for viral replication.
0 kommentar(er)
