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 bo x'' family of putative RNA-dependent ATPases and helicases. The protei n was purified from Escherichia coli and determined to be an RNA-depen dent ATPase. The ATPase activity is 7-fold more specific for full-leng th 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 smal l nuclear ribonucleoprotein. We propose that this conformational chang e makes the branch point pairing sequence of U2 RNA accessible for pai ring with the intron allowing formation of the pre-spliceosome.