Two kinds of new acridine-DNA conjugates were synthesized by attaching acridines with bulky substituents to the end of DNA. These conjugates were hybridized to complementary RNA in combination with another unmodified DNA that hybridize to the adjacent fraction of the RNA, and were used as site-selective RNA activators for site-selective RNA cleavage catalyzed by Lu-III. The site-selective hydrolyses by these combinations are several times as fast as that achieved with the use of commercially available acridine moiety.