title: DExD/H-box Prp5 protein is in the spliceosome during most of the splicing cycle.
abstract: The DExD/H-box Prp5 protein (Prp5p) is an essential, RNA-dependent ATPase required for pre-spliceosome formation during nuclear pre-mRNA splicing. In order to understand how this protein functions, we used in vitro, biochemical assays to examine its association with the spliceosome from Saccharomyces cerevisiae. GST-Prp5p in splicing assays pulls down radiolabeled pre-mRNA as well as splicing intermediates and lariat product, but reduced amounts of spliced mRNA. It cosediments with active spliceosomes isolated by glycerol gradient centrifugation. In ATP-depleted extracts, GST-Prp5p associates with pre-mRNA even in the absence of spliceosomal snRNAs. Maximal selection in either the presence or absence of ATP requires a pre-mRNA with a functional intron. Prp5p is present in the commitment complex and functions in subsequent pre-spliceosome formation. Reduced Prp5p levels decrease levels of commitment, pre-spliceosomal and spliceosomal complexes. Thus Prp5p is most likely an integral component of the spliceosome, being among the first splicing factors associating with pre-mRNA and remaining until spliceosome disassembly. The results suggest a model in which Prp5p recruits the U2 snRNP to pre-mRNA in the commitment complex and then hydrolyzes ATP to promote stable association of U2 in the pre-spliceosome. They also suggest that Prp5p could have multiple ATP-independent and ATP-dependent functions at several stages of the splicing cycle.
authors.affiliation: Department of Molecular Genetics and Microbiology, Albuquerque, New Mexico 87131, USA.
authors.forename: Tomasz R
authors.initials: TR
authors.lastname: Kosowski
authors.forename: Heather R
authors.initials: HR
authors.lastname: Keys
authors.forename: Tiffani K
authors.initials: TK
authors.lastname: Quan
authors.forename: Stephanie W
authors.initials: SW
authors.lastname: Ruby
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D015153:Blotting, Western; D053487:DEAD-box RNA Helicases / Q000235:genetics* / Q000378:metabolism; D012322:RNA Precursors / Q000235:genetics* / Q000378:metabolism; D012326:RNA Splicing; D012342:RNA, Small Nuclear / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017413:Ribonucleoprotein, U2 Small Nuclear / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism*; D017381:Spliceosomes / Q000502:physiology*; D013696:Temperature; D014158:Transcription, Genetic
chemical_list: D012322:RNA Precursors; D012342:RNA, Small Nuclear; D011993:Recombinant Fusion Proteins; D017413:Ribonucleoprotein, U2 Small Nuclear; D029701:Saccharomyces cerevisiae Proteins; C405484:U2 small nuclear RNA; D000255:Adenosine Triphosphate; C064447:PRP5 protein, S cerevisiae; D053487:DEAD-box RNA Helicases