title: Function of the ski4p (Csl4p) and Ski7p proteins in 3'-to-5' degradation of mRNA.
abstract: One of two general pathways of mRNA decay in the yeast Saccharomyces cerevisiae occurs by deadenylation followed by 3'-to-5' degradation of the mRNA body. Previous results have shown that this degradation requires components of the exosome and the Ski2p, Ski3p, and Ski8p proteins, which were originally identified due to their superkiller phenotype. In this work, we demonstrate that deletion of the SKI7 gene, which encodes a putative GTPase, also causes a defect in 3'-to-5' degradation of mRNA. Deletion of SKI7, like deletion of SKI2, SKI3, or SKI8, does not affect various RNA-processing reactions of the exosome. In addition, we show that a mutation in the SKI4 gene also causes a defect in 3'-to-5' mRNA degradation. We show that the SKI4 gene is identical to the CSL4 gene, which encodes a core component of the exosome. Interestingly, the ski4-1 allele contains a point mutation resulting in a mutation in the putative RNA binding domain of the Csl4p protein. This point mutation strongly affects mRNA degradation without affecting exosome function in rRNA or snRNA processing, 5' externally transcribed spacer (ETS) degradation, or viability. In contrast, the csl4-1 allele of the same gene affects rRNA processing but not 3'-to-5' mRNA degradation. We identify csl4-1 as resulting from a partial-loss-of-function mutation in the promoter of the CSL4 gene. These data indicate that the distinct functions of the exosome can be separated genetically and suggest that the RNA binding domain of Csl4p may have a specific function in mRNA degradation.
authors.affiliation: Department of Molecular and Cellular Biology and Howard Hughes Medical Institute, University of Arizona, Tucson, Arizona 85721, USA. ambro@u.arizona.edu
authors.forename: A
authors.initials: A
authors.lastname: van Hoof
authors.forename: R R
authors.initials: RR
authors.lastname: Staples
authors.forename: R E
authors.initials: RE
authors.lastname: Baker
authors.forename: R
authors.initials: R
authors.lastname: Parker
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000483:Alleles; D000595:Amino Acid Sequence; D001665:Binding Sites; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins; D005690:Galactose / Q000378:metabolism; D005838:Genotype; D005947:Glucose / Q000378:metabolism; D049452:Green Fluorescent Proteins; D007763:Lac Operon; D008164:Luminescent Proteins / Q000378:metabolism; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D010641:Phenotype; D010957:Plasmids / Q000378:metabolism; D017354:Point Mutation; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000378:metabolism; D012340:RNA, Ribosomal, 5.8S / Q000378:metabolism; D012342:RNA, Small Nuclear / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D013395:Sucrose / Q000378:metabolism; D013696:Temperature; D013997:Time Factors; D014158:Transcription, Genetic
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C112809:CSL4 protein, S cerevisiae; D005656:Fungal Proteins; D008164:Luminescent Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D012335:RNA, Ribosomal; D012340:RNA, Ribosomal, 5.8S; D012342:RNA, Small Nuclear; D011993:Recombinant Fusion Proteins; C118668:SKI7 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C405482:U4 small nuclear RNA; D049452:Green Fluorescent Proteins; D013395:Sucrose; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D005947:Glucose; D005690:Galactose