RNase H-mediated degradation of pre-formed ASO:RNA duplexes and in vitro-synthesized RNAs targeted by ASOs.

(A) Schematic of the experimental setup for panels B and C. Applicable for some ASOs: Y, 8-oxo-dG residue; +, LNA sugar base. (B, C) Cleavage of pre-formed ASO:target RNA duplexes by RNase H. (B) Five femtomoles of ³³P-labeled substrate was treated with RNase H for the indicated times. The reaction products were collected, denatured by heating at 95°C for 2 min and analyzed by PAGE in native 15% gels. Arrows at right point to the substrate (S) and major cleavage product(s) (P). Results from one of three independent reproducible experiments are shown. (C) Kinetics of RNase H cleavage of different ASO:RNA duplexes. The amounts of radioactivity remaining in the uncleaved substrate were quantified using a Typhoon Trio instrument. Quantifications were performed for each gel. The obtained values were normalized to the radioactivity present in the substrate before adding RNase H (set to 100%). Each point corresponds to the average of three independent experiments. Error bars indicate the standard deviation. (D) Cleavage of FR3131 RNA by RNase H in the presence of different ASOs. The RNA and ASOs were mixed and incubated at 37°C for 10 min; then, RNase H was added to the reaction mixture. RNA samples were collected at the indicated time points and analyzed by electrophoresis in native 0.8% TAE agarose gels. The results from one of three independent reproducible experiments are shown. S: substrate; P1 and P2: cleavage products.