7SL RNA down regulation by over expression of SRP19 does not inhibit APOBEC3F and 3G encapsidation and antiviral effect. A. Effect of SRP19 overexpression on virus production and infectivity. HIV-1 ΔVif lentiviral vector particles were produced by transient transfection of 293T cells, adding indicated amounts of APOBEC3G, 3F, SRP19 and SRP19 Δ6 plasmids. Virion production (white columns) and infectivity (gray columns) were assessed by measuring reverse transcriptase activity in the supernatant and performing a single round transduction assay, respectively. SRP19 overexpression affects neither HIV particle release nor the antiviral action of APOBEC3G and 3F. Results are representative of three independent experiments. B. SRP19 over expression inhibits 7SL RNA virion incorporation. HIV genomic (white columns) and 7SL RNA (gray columns) levels in virions produced as described in (A) were quantified by real time PCR. Amounts measured in virions produced from cells transfected with ΔVif HIV1 alone were given the arbitrary value of 100. SRP19 overexpression drastically reduces 7SL RNA levels in virions, in spite of having no measurable effect on the intracellular levels of this RNA species (not illustrated). Representative of three independent experiments. C. SRP19 overexpression does not impair APOBEC3F/3G virion incorporation. Western blot analysis of viral and cellular extracts after transient transfection of 293T cells as described in (A), using indicated antibodies. The normal virion incorporation of A3G and A3F corroborates the absence of effect of SRP19 overexpression on the antiviral action of the cytidine deaminases (A).