Stable mRNP formation and export require cotranscriptional recruitment of the mRNA export factors Yra1p and Sub2p by Hpr1p.
Yra1p/REF participates in mRNA export by recruiting the export receptor Mex67p to messenger ribonucleoprotein (mRNP) complexes. Yra1p also binds Sub2p, a DEAD box ATPase/RNA helicase implicated in splicing and required for mRNA export. We identified genetic and physical interactions between Yra1p, Sub2p, and Hpr1p, a protein involved in transcription elongation whose deletion leads to poly(A)(+) RNA accumulation in the nucleus. By chromatin immunoprecipitation (ChIP) experiments, we show that Hpr1p, Sub2p, and Yra1p become associated with active genes during transcription elongation and that Hpr1p is required for the efficient recruitment of Sub2p and Yra1p. The data indicate that transcription and export are functionally linked and that mRNA export defects may be due in part to inefficient loading of essential mRNA export factors on the growing mRNP. We also identified functional interactions between Yra1p and the exosome components Rrp45p and Rrp6p. We show that yra1, sub2, and Deltahpr1 mutants all present defects in mRNA accumulation and that deletion of RRP6 in yra1 mutants restores normal mRNA levels. The data support the hypothesis that an exosome-dependent surveillance mechanism targets improperly assembled mRNPs for degradation.
Zenklusen
Daniel
D
Institute of Microbiology, University of Lausanne, 1011 Lausanne, Switzerland.
Vinciguerra
Patrizia
P
Wyss
Jean-Christophe
JC
Stutz
Françoise
F
D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D017930:Genes, Reporter; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism*; D011485:Protein Binding; D006180:Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism; D020365:RNA Helicases / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012261:Ribonucleoproteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; C063494:HPR1 protein, S cerevisiae; D009687:Nuclear Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D012261:Ribonucleoproteins; D029701:Saccharomyces cerevisiae Proteins; C105887:YRA1 protein, S cerevisiae; C026452:messenger ribonucleoprotein; D000251:Adenosine Triphosphatases; C092477:PMA1 protein, S cerevisiae; C027900:RNA-dependent ATPase; D006180:Proton-Translocating ATPases; D020365:RNA Helicases