Encapsidation efficiency of the Psi and DIS HIV-2 mutants. (A) Size of the protected fragment corresponding to the viral genomic RNA when using the KS2ΨKE riboprobe in an RNAse protection assay (RPA). Protected mutant genomic RNAs vary in size between 329 and 355 nt due to the position of the mutations. (B) Representative RPA where 2 μg of cytoplasmic RNA and an equivalent of 2.5 × 106 cpm of virion RNA was probed with 1 × 105 cpm of KS2ΨKE riboprobe. Samples were also probed with 1 × 105 cpm of KS2ΨEP and GAPDH riboprobes to detect plasmid DNA contamination and control for the loading, respectively. WT, wild type; DM, Psi deletion mutant; SM1, DIS mutant; SM2, pal mutant; mock, mock transfection; Y, yeast RNA + RNase; I, yeast RNA – RNAse (diluted 1:10); M, Century Plus RNA Markers (Ambion). (C) Packaging efficiencies of mutant HIV-2 relative to WT virus. Data from 3 independent experiments are shown, error bars correspond to the SD. *, Student t test p value < 0.005.