5246 Nucleic Acids Research, 2010, Vol. 38, No. 15 Figure 2. PR gene expression can be silenced by agRNAs containing 20F-RNA. (A) Duplex sequences: passenger strands are listed on top in all cases; for siRNA PR2526 this is the sense strand, but for agRNAs PR-9 and PR-26 this is the antisense strand. Modiﬁcation codes: dna, RNA, 20F-RNA; p = phosphate. (B) PR-9 analogs and controls containing one strand heavily or fully modiﬁed with 20F-RNA. (C) PR-9 analogs and controls containing a minimally 20F-RNA-modiﬁed guide strand. (D) PR-26 analogs containing one or both strands heavily or fully modiﬁed with 20F-RNA. All data are normalized to mismatch control MM4. RNA levels are the average (±SD) from at least two independent transfections. *P < 0.05, **P < 0.01, ***P < 0.005. Protein levels were also conﬁrmed by at least two independent transfections, from which a typical western blot is shown.