Figure 5

Sequence signal for off-target effects: small interfering (si)RNA seed matches against the 3' untranslated region (UTR) of transforming growth factor-β receptor 2 (TGFBR2) decreased with rank in the screen. The effects were predominantly mediated by the guide strand, and hexamer seed matches were not effective. (A) Moving average of the percentage of siRNA guide strand seed matched to the 3' UTR of the receptors as a function of siRNA rank in the screen (window: 500). (B) Off-target effects against transforming growth factor-β receptor 1 (TGFBR1) and TGFBR2 were mediated predominantly by 3' UTR matches of the siRNA guide strand, but to a small extent by the passenger strand. Enrichment of heptamer seed matches of the guide and passenger siRNA strands to TGFBR1 (left) and TGFBR2 (right) 3' UTRs are shown for siRNAs with a confirmed effect on TGFBR1 and TGFBR2. (C) Heptamer, not hexamer, seed matches were responsible for TGFBR2 silencing. When we analyzed only for the presence of hexamer seed matches that were not part of a heptamer match, there was no enrichment in the TGFBR2 hit siRNA compared with control siRNA.