Article
- The EMBO Journal (2007) 26, 2317 - 2326
- doi:10.1038/sj.emboj.7601669
Published online: 5 April 2007
Subject Category:
Dissecting mechanisms of nuclear mRNA surveillance in THO/sub2 complex mutants
Mathieu Rougemaille1, Rajani Kanth Gudipati1,2, Jens Raabjerg Olesen2,a, Rune Thomsen2, Bertrand Seraphin1, Domenico Libri1,2 and Torben Heick Jensen2
- Centre National de la Recherche Scientifique, Centre de Genetique Moleculaire, Gif sur Yvette, France
- Department of Molecular Biology, Centre for mRNP Biogenesis and Metabolism, Aarhus University, Arhus C, Denmark
Correspondence to:
Torben Heick Jensen, Department of Molecular Biology, Centre for mRNP Biogenesis and Metabolism, University of Aarhus, CF Møllers Alle, Bldg 130, Aarhus, Aarhus C 8000, Denmark. Tel.: +45 8942 2609; Fax: +45 8619 6500; E-mail: thj@mb.au.dk
Domenico Libri, Centre National de la Recherche Scientifique, Centre de Genetique Moleculaire, Gif sur Yvette, France. Tel.: +33 1 698 23809; Fax: +33 1 698 23877; E-mail: libri@cgm.cnrs-gif.fr
aPresent address: Hoiberg A/S, Store Kongesgade 59A, 1264 Copenhagen K, Denmark.
Received 27 September 2006; Accepted 7 March 2007
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.
Keywords:
- mRNA surveillance,
- nuclear exosome,
- RNA degradation,
- RNA retention,
- TRAMP
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