We have previously reported that 2′-O-methyl RNAs are efficient probes for duplex DNA. Here we describe the design, synthesis, and DNA cleaving activity of 1,10-phenanthroline (OP)-linked 2′-O-methyl RNA (OP-m). Although a local triple helix was formed, both with OP-m and a control OP-linked DNA at the target sequence of the duplex DNA, the promoter region of the human thrombomodulin gene, the cleavage efficiencies on both strands were not proportional when OP-m was used as a cleavage agent. These results may reflect the structural differences of the respective triple helices and the duplex-triplex junction, formed from the two types of triplex-forming oligonucleotides, 2′-O-methyl RNA and DNA. Since the OP-ms were found to work as preferential purine-strand cutters for duplex DNA, they would be useful as unique tools for genome analysis.
