HIV-1 genomic constructs and requirements for Vpr virion packaging. A) All viral constructs were based on the p89.6/HA-Ub/R+. Pr-/R+: genomic construct carrying the wild type p6 and a premature stop codon for the protease ORF immediately after the p6 stop codon. All other clones were derived from the Pr-/R+ construct. Bold-typed regions represent binding sites for Tsg101, Vpr (this study), and AIP1. B) Effects of p6 mutations on virion packaging of Vpr. Experimental conditions are described in "Findings". Left panels: Gag and Vpr Western blots with virion samples. Right panels: top two panels are Western blots of virion samples, whereas the bottom panel is Western blot of Vpr immunoprecipitated from cell lysates. C) Comparision of the 15FxFG domain in HIV-1 Gag p6 with the FxFG domains in human Pom121. HIV-1 p6 sequence is derived from isolate 89.6 , and the human Poml21 sequence is derived from GenBank accession number BC008794. Numbers indicate the amino acid positions in the proteins.