Adriamycin inhibits human RH II/Gu RNA helicase activity by binding to itssubstrate

RNA helicases are enzymes important in RNA synthesis, processing, transport , and turnover. Human nucleolar RNA helicase II/Gu protein (RH II/Gu) was e xpressed in a baculovirus system. The purified recombinant RH II/Gu protein has RNA helicase activity on a 5' tailed ds RNA substrate in vitro. We fou nd that Adriamycin, a widely used anticancer drug, inhibited RH II/Gu helic ase activity in a dose-dependent manner with an IC50 of 40 mu M. Adriamycin bound to the RNA substrate, and the binding was disrupted by boiling or tr eatment with 1% SDS, suggesting that the binding of Adriamycin to RNA is re versible. Adriamycin was also found by gel electrophoresis to bind to yeast tRNA to form slow-migrating complexes. These results suggest that Adriamyc in can inhibit RNA synthesis or processing by binding to RNA substrates, (C ) 1990 Academic Press.