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An early function during transcription for the yeast mRNA export factor Dbp5p/Rat8p suggested by its genetic and
Francisco Estruch1, Charles N Cole
1Departments of Biochemistry and Genetics, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
Abstract:
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.
Insights
The yeast DEAD-box protein Dbp5p is crucial for mRNA export. New findings reveal Dbp5p also plays a nuclear role in early transcription, interacting with transcription machinery.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- Dbp5p (also known as Rat8p) is an essential yeast DEAD-box protein involved in mRNA export.
- It localizes to the nuclear pore complex, suggesting a role in releasing mRNA-associated proteins during nuclear export.
Purpose of the Study:
- To investigate potential roles of Dbp5p beyond mRNA export.
- To explore the relationship between Dbp5p and the transcription machinery.
Main Methods:
- Genetic interaction screens were performed between DBP5 and genes involved in transcription.
- Physical association of Dbp5p with transcription factor IIH was assessed.
- The dependence of Dbp5p mutant phenotypes on the RNA polymerase II carboxy-terminal domain was examined.
Main Results:
- Genetic screens revealed interactions between DBP5 and genes regulating transcription initiation and promoter clearance.
- Mutations impairing transcription suppressed dbp5 mutants, while mutations enhancing transcription were synthetically lethal.
- Dbp5p physically associates with components of transcription factor IIH, and its function is linked to the RNA polymerase II carboxy-terminal domain.
Conclusions:
- Dbp5p is implicated in the early stages of transcription, in addition to its known role in mRNA export.
- These findings suggest a functional link between Dbp5p and the transcription machinery, potentially coordinating transcription with export.
- Dbp5p may have a nuclear function during the early steps of transcription.