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Nab2p and the Thp1p-Sac3p complex functionally interact at the interface between transcription and mRNA metabolism.

THP1 is a conserved eukaryotic gene whose null mutations confer, in yeast, transcription and genetic instability phenotypes and RNA export defects similar to those of the THO/TREX complex null mutations. In a search for multicopy suppressors of the transcription defect of thp1Delta cells, we identified the poly(A)+ RNA-binding heterogeneous nuclear ribonucleoprotein Nab2p. Multicopy NAB2 also suppressed the RNA export defect of thp1Delta cells. This result suggests a functional relationship between Thp1p and Nab2p. Consistently, the leaky mutation nab2-1 conferred a transcription defect and hyper-recombination phenotype similar to those of thp1Delta, although to a minor degree. Reciprocally, a purified His6-tagged Thp1p fusion bound RNA in vitro. In a different approach, we show by Western analyses that a highly purified Thp1p-Sac3p complex does not contain components of THO/TREX and that sac3Delta confers a transcription defect and hyper-recombination phenotype identical to those of thp1Delta. mRNA degradation was not affected in thp1Delta mutants, implying that their expression defects are not due to mRNA decay. This indicates that Thp1p-Sac3p is a structural and functional unit. Altogether, our results suggest that Thp1p-Sac3p and Nab2p are functionally related heterogeneous nuclear ribonucleoproteins that define a further link between mRNA metabolism and transcription.

Pubmed ID: 12702719


  • Gallardo M
  • Luna R
  • Erdjument-Bromage H
  • Tempst P
  • Aguilera A


The Journal of biological chemistry

Publication Data

June 27, 2003

Associated Grants

  • Agency: NCI NIH HHS, Id: P30 CA08748

Mesh Terms

  • Fungal Proteins
  • Heterogeneous-Nuclear Ribonucleoproteins
  • Nuclear Proteins
  • Nucleocytoplasmic Transport Proteins
  • Phenotype
  • Porins
  • RNA, Messenger
  • RNA-Binding Proteins
  • Recombination, Genetic
  • Ribonucleoproteins
  • Saccharomyces cerevisiae Proteins
  • Transcription, Genetic