An early function during transcription for the yeast mRNA export factor Dbp5p/Rat8p suggested by its genetic and physical interactions with transcription factor IIH components.
The yeast DEAD-box protein Dbp5p/Rat8p is an essential factor for mRNA export and shuttles between the nucleus and the cytoplasm. It is concentrated at the cytoplasmic fibrils of the nuclear pore complex where it interacts with several nucleoporins. On the basis of this localization, it has been suggested that it might participate in a terminal step of RNA export, the release from the mRNA of proteins that accompany the mRNA during translocation through nuclear pores. In this report, we present evidence linking Dbp5p to transcription. Two different screens identified genetic interactions between DBP5 and genes involved in early transcription events, initiation and promoter clearance. Mutations of transcription proteins expected to impair transcription act as suppressors of dbp5 mutants, whereas those that may act to increase transcription are synthetically lethal with dbp5 mutations. We also show that growth and mRNA export in dbp5 mutant strains are dependent on the carboxy-terminal domain of the RNA pol II largest subunit. Finally, we show that Dbp5p associates physically with components of transcription factor IIH. Because these interactions affect not only growth but also mRNA export, they are likely to reflect a functional relationship between Dbp5p and the transcription machinery. Together, our results suggest a nuclear role for Dbp5 during the early steps of transcription.
Estruch
Francisco
F
Departments of Biochemistry and Genetics, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
Cole
Charles N
CN
D021581:Active Transport, Cell Nucleus; D053487:DEAD-box RNA Helicases; D005800:Genes, Fungal; D016153:Genes, Suppressor; D009154:Mutation; D029543:Nucleocytoplasmic Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020365:RNA Helicases / Q000235:genetics* / Q000378:metabolism*; D012331:RNA, Fungal / Q000235:genetics* / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism*; D017384:Sequence Deletion; D035381:TATA-Binding Protein Associated Factors; D035362:Transcription Factor TFIID; D051758:Transcription Factor TFIIH; D019473:Transcription Factors, TFII / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic
D029543:Nucleocytoplasmic Transport Proteins; D012331:RNA, Fungal; D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; C490039:TAF6 protein, S cerevisiae; D035381:TATA-Binding Protein Associated Factors; D035362:Transcription Factor TFIID; D019473:Transcription Factors, TFII; D051758:Transcription Factor TFIIH; D011494:Protein Kinases; C060137:carboxy-terminal domain kinase; C492382:DBP5 protein, S cerevisiae; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases