Viral protein R regulates nuclear import of the HIV-1 pre-integration complex

Serguei Popov, Michael Rexach, Gabriele Zybarth, Norbert Railing, May Ann Lee, Lee Ratner, Cynthia M. Lane, Mary Shannon Moore, Günter Blobel, Michael Bukrinsky

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278 Scopus citations


Replication of human immunodeficiency virus type 1 (HIV-1) in non-dividing cells critically depends on import of the viral pre-integration complex into the nucleus. Genetic evidence suggests that viral protein R (Vpr) and matrix antigen (MA) are directly involved in the import process. An in vitro assay that reconstitutes nuclear import of HIV-1 pre-integration complexes in digitonin-permeabilized cells was used to demonstrate that Vpr is the key regulator of the viral nuclear import process. Mutant HIV-1 pre-integration complexes that lack Vpr failed to be imported in vitro, whereas mutants that lack a functional MA nuclear localization sequence (NLS) were only partially defective. Strikingly, the import defect of the Vpr- mutant was rescued when recombinant Vpr was re-added. In addition, import of Vpr- virus was rescued by adding the cytosol of HeLa cells, where HIV-1 replication had been shown to be Vpr-independent. In a solution binding assay, Vpr associated with karyopherin α, a cellular receptor for NLSs. This association increased the affinity of karyopherin a for basic-type NLSs, including that of MA, thus explaining the positive effect of Vpr on nuclear import of the HIV-1 pre-integration complex and BSA-NLS conjugates. These results identify the biochemical mechanism of Vpr function in transport of the viral pre-integration complex to, and across, the nuclear membrane.

Original languageEnglish
Pages (from-to)909-917
Number of pages9
JournalEMBO Journal
Issue number4
StatePublished - Feb 4 1998


  • HIV-1
  • Karyopherin α
  • Matrix protein
  • Nuclear import
  • Vpr


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