The Saccharomyces cerevisiae Prp5 Protein Has RNA-dependent ATPase Activity with Specificity for U2 Small Nuclear RNA

The Saccharomyces cerevisiae protein Prp5 is a member of the “DEAD box” family of putative RNA-dependent ATPases and helicases. The protein was purified from Escherichia coli and determined to be an RNA-dependent ATPase. The ATPase activity is 7-fold more specific for full-length U2 than for any of the other small nuclear RNAs or nonspecific RNAs tested. An RNaseH assay in extracts was used to demonstrate that Prp5 mediates an ATP-dependent conformational change in the intact U2 small nuclear ribonucleoprotein. We propose that this conformational change makes the branch point pairing sequence of U2 RNA accessible for pairing with the intron allowing formation of the pre-spliceosome.