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.
Gallardo
Mercedes
M
Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Avenida Reina Mercedes 6, 41012 Sevilla, Spain.
Luna
Rosa
R
Erdjument-Bromage
Hediye
H
Tempst
Paul
P
Aguilera
Andres
A
D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D018272:Porins; D012333:RNA, Messenger / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D011995:Recombination, Genetic; D012261:Ribonucleoproteins / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
D005656:Fungal Proteins; D034441:Heterogeneous-Nuclear Ribonucleoproteins; C080773:NAB2 protein, S cerevisiae; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D018272:Porins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; C103382:SAC3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C476348:Thp1 protein, S cerevisiae; C026452:messenger ribonucleoprotein