title: Dissecting mechanisms of nuclear mRNA surveillance in THO/sub2 complex mutants.
abstract: The nuclear exosome is involved in numerous RNA metabolic processes. Exosome degradation of rRNA, snoRNA, snRNA and tRNA in Saccharomyces cerevisiae is activated by TRAMP complexes, containing either the Trf4p or Trf5p poly(A) polymerase. These enzymes are presumed to facilitate exosome access by appending oligo(A)-tails onto structured substrates. Another role of the nuclear exosome is that of mRNA surveillance. In strains harboring a mutated THO/Sub2p system, involved in messenger ribonucleoprotein particle biogenesis and nuclear export, the exosome-associated 3' --> 5' exonuclease Rrp6p is required for both retention and degradation of nuclear restricted mRNAs. We show here that Trf4p, in the context of TRAMP, is an mRNA surveillance factor. However, unlike Rrp6p, Trf4p only partakes in RNA degradation and not in transcript retention. Surprisingly, a polyadenylation-defective Trf4p protein is fully active, suggesting polyadenylation-independent mRNA degradation. Transcription pulse-chase experiments show that HSP104 molecules undergoing quality control in THO/sub2 mutant strains fall into two distinct populations: One that is quickly degraded after transcription induction and another that escapes rapid decay and accumulates in foci associated with the HSP104 transcription site.
authors.affiliation: Centre National de la Recherche Scientifique, Centre de Genetique Moleculaire, Gif sur Yvette, France.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Rougemaille
authors.forename: Rajani Kanth
authors.initials: RK
authors.lastname: Gudipati
authors.forename: Jens Raabjerg
authors.initials: JR
authors.lastname: Olesen
authors.forename: Rune
authors.initials: R
authors.lastname: Thomsen
authors.forename: Bertrand
authors.initials: B
authors.lastname: Seraphin
authors.forename: Domenico
authors.initials: D
authors.lastname: Libri
authors.forename: Torben Heick
authors.initials: TH
authors.lastname: Jensen
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D005095:Exoribonucleases / Q000378:metabolism; D063326:Exosome Multienzyme Ribonuclease Complex; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D046912:Multiprotein Complexes; D009154:Mutation; D009687:Nuclear Proteins; D026723:Polyadenylation; D020871:RNA Stability / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D004268:DNA-Binding Proteins; C063494:HPR1 protein, S cerevisiae; D006360:Heat-Shock Proteins; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D012333:RNA, Messenger; D012261:Ribonucleoproteins; D029701:Saccharomyces cerevisiae Proteins; C405934:THO2 protein, S cerevisiae; C476348:Thp1 protein, S cerevisiae; D014157:Transcription Factors; C068359:MFT1 protein, S cerevisiae; C070972:HsP104 protein, S cerevisiae; D004259:DNA-Directed DNA Polymerase; C487545:PAP2 protein, S cerevisiae; D005095:Exoribonucleases; D063326:Exosome Multienzyme Ribonuclease Complex; C112610:RRP6 protein, S cerevisiae; D000251:Adenosine Triphosphatases; C027900:RNA-dependent ATPase