293T transfectants (6.0 Â 10 5 cells) stably expressing the (-1) and (0) dual-luciferase HIV reporter were transfected with 150 ng of the PKR ShortCut Õ siRNA Mix or the eGFP ShortCut Õ siRNA Mix (New England BioLabs), using PEI. The TAR-expressing plasmids were transfected 24 h after the transfection with a siRNA mix. Cells were harvested 48 h after this second transfection and luciferase assays were performed.