Figure 4. A 2′-O-Methyl Oligonucleotide Is a Potent Inhibitor of RNAi in Human Cultured HeLa Cells.

(A–D) HeLa cells were transfected with 1 nM (A), 5 nM (B), 10 nM (C), or 25 nM (D) siRNA-targeting Pp-luc mRNA. The next day the cells were cotransfected with Rr-luc-and Pp-luc-expressing plasmids together with various amounts of a 31-nt 2′-O-methyl oligonucleotide complementary to the antisense strand of the siRNA. The half-maximal concentration of 2′-O-methyl oligonucleotide required to inhibit (IC₅₀) was determined by fitting the data to a sigmoidal curve using a Hill coefficient of 1.

(E) IC₅₀ plotted as a function of the concentration of transfected siRNA.