Analyses of viral stocks generated from transfection in 293T cells. 293T cells were seeded in a 6-well plate and transfected with 2 μg pNL4-3 let7 scr, pNL4-3 let7a, pNL4-3 miR28, pNL4-3 miR29b, pNL4-3 miR138, pNL4-3 miR211, pNL4-3 miR326 and pNL4-3 miR329. Supernatants were harvested at 48 hours post transfection and filtered to remove any contaminating cells. Supernatants were used to infect the HeLa derived TZMbl reporter cell line and to determine reverse transcriptase (RT) activity. Twenty-four hours after infection, the TZMBl cells were fixed and infected cells were visualized by β-galactosidase staining. Infectious units (IU)/RT were determined and graphed relative to NL4-3 let7 scr control. Data shown are the averages of three replicates. ** indicates a p-value < 0.01 and *** indicates a p-value < 0.001 compared to control.