Mutations in HIV-2 packaging signal, but not in the DIS, render the RNA monomeric in vivo. (A) Native northern blot analysis of HIV-2 genomic RNA extracted from pelleted virions 48 h after COS-1 cell transfection. RNA inputs were normalised on RT activity and an equivalent to 2.5 × 106 cpm was used. WT, wild type; DM, Psi deletion mutant; SM1, DIS mutant; SM2, Psi pal mutant; mock, mock transfection; MM, Millennium RNA Markers (Ambion); M, monomer; D, dimer. (B) Bar chart representing the percentage of dimer present in each virion RNA sample. Data from at least three independent experiments are shown, error bars correspond to the SD. *, Student t test p value < 0.05.