Background: During pre-mRNA splicing, dynamic rearrangement of RNA sec
ondary structure within the spliceosome is crucial for intron recognit
ion and formation of the catalytic core. Splicing factors belonging to
the DExD/DExH-box family of RNA-dependent ATPases are thought to have
a central role in directing these rearrangements by unwinding RNA hel
ices. Proof of this hypothesis has, however, been conspicuously lackin
g. Results: Prp16 is a DEAH-box protein that functions in the second s
tep of splicing in vitro. Using various RNA duplexes as substrate, we
have shown that Prp16 has an ATP-dependent RNA unwinding activity. Thi
s activity is independent of sequence in either the single-stranded or
duplexed regions of the RNA substrate. A mutation (prp16-1) near the
ATP-binding motif of Prp16 inhibits both the RNA-dependent ATPase acti
vity and the ATP-dependent RNA unwinding activity. Conclusions: Our fi
ndings provide strong biochemical evidence that Prp16 can disrupt a du
plexed RNA structure on the spliceosome. Because the purified protein
lacks sequence specificity in unwinding RNA duplexes, targeting of the
unwinding activity of Prp16 in the spliceosome is likely to be determ
ined by other interacting protein factors. The demonstration of unwind
ing activity will also help our understanding of how the fidelity of b
ranchpoint recognition is controlled by Prp16. (C) Current Biology Ltd
ISSN 0960-9822.