shRNA vectors and their reporter targets, and the efficacy of siRNAs compared to equivalent molecules expressed as shRNAs. (A) Schematic representation of the single U6/shRNA constructs and their target Luciferase reporter vectors used in this study. A total of 6 different shRNA sequences were cloned downstream of the U6 promoter. Using psi-CHECK-2, five different reporter vectors were constructed that encode Firefly luciferase and each of the shRNA target sequences fused to Renilla luciferase (except psi-CHK-4 as Renilla luciferase was the shRNA target sequence). For each reporter vector, the shRNA that targets each is indicated. (B) Normalised ratios of the Renilla:Firefly luciferase activity when DF-1 cells were co-transfected with the indicated reporter plasmids and either 50 nM of siRNAs or 125 ng of shRNA plasmid DNA. Values for siRNAs are shown as percentages of the negative control siRNA (si-NS), and values for shRNAs are shown as percentages of the negative control shRNA (sh-NS), as the mean of 4 replicates ± standard error.