The DExD-box RNA helicase Dbp7 unwinds short double-stranded RNAs

DExD-box proteins are ATP-dependent enzymes that unwind double-stranded RNAs in a non-processive manner, often initiating strand separation from 5'- or 3'-single-stranded overhangs. Dbp7, a member of this family, is required for yeast ribosome biogenesis and has been specifically implicated in the release of the small nucleolar RNA snR190 from early pre-60S particles. To gain mechanistic insight into its function, we have examined the in vitro helicase activity of recombinant Dbp7. We show that it efficiently unwinds short double-stranded RNA substrates in an ATP-dependent manner, irrespective of overhang polarity, thereby establishing it as a bona fide DExD-box RNA helicase.