title: U4 small nuclear RNA dissociates from a yeast spliceosome and does not participate in the subsequent splicing reaction.
abstract: U4 and U6 small nuclear RNAs reside in a single ribonucleoprotein particle, and both are required for pre-mRNA splicing. The U4/U6 and U5 small nuclear ribonucleoproteins join U1 and U2 on the pre-mRNA during spliceosome assembly. Binding of U4 is then destabilized prior to or concomitant with the 5' cleavage-ligation. In order to test the role of U4 RNA, we isolated a functional spliceosome by using extracts prepared from yeast cells carrying a temperature-sensitive allele of prp2 (rna2). The isolated prp2 delta spliceosome contains U2, U5, U6, and possibly also U1 and can be activated to splice the bound pre-mRNA. U4 RNA does not associate with the isolated spliceosomes and is shown not to be involved in the subsequent cleavage-ligation reactions. These results are consistent with the hypothesis that the role of U4 in pre-mRNA splicing is to deliver U6 to the spliceosome.
authors.affiliation: Department of Microbiology, University of Texas, Austin 78712-1095.
authors.forename: S L
authors.initials: SL
authors.lastname: Yean
authors.forename: R J
authors.initials: RJ
authors.lastname: Lin
mesh_terms: D015152:Blotting, Northern; D012322:RNA Precursors / Q000235:genetics*; D012326:RNA Splicing; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism*; D012342:RNA, Small Nuclear / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000378:metabolism; D017411:Ribonucleoproteins, Small Nuclear; D012441:Saccharomyces cerevisiae / Q000235:genetics*
chemical_list: D012322:RNA Precursors; D012331:RNA, Fungal; D012342:RNA, Small Nuclear; D012261:Ribonucleoproteins; D017411:Ribonucleoproteins, Small Nuclear