PIs activate latent HIV-1 transcription. A. OM-10.1 cells were treated with PIs as indicated and proteasome activity was assessed two hours post-treatment. The values shown specify the percent proteasome function compared to untreated cells, whose function was set to 100%. B. OM-10.1 cells were treated with 15nM Velcade for the indicated time course. At each time point, nef RNA levels were analyzed via reverse transcription-quantitative PCR. RNA expression values were calculated via ΔΔC(t) method with the values normalized to the expression level of GAPDH in each sample. C. OM-10.1 cells were treated with PIs as indicated and nef RNA and D. env RNA levels were analyzed 72 hours post-treatment via reverse transcription-quantitative PCR (values calculated as above). Error bars indicate SEM. Asterisks indicate a significant difference (* p<0.05; ** p<0.01; *** p<0.001) in RNA expression levels between drug-treated cells and DMSO-treated (negative control) cells. P-values calculated using one-tailed Student’s t test. Cells were treated with SAHA as a positive control. Velcade was used in three different concentrations where indicated to illustrate concentration dependence. The figure represents average values from three independent experiments.