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Processing of 3'-extended read-through transcripts by the exosome can generate functional mRNAs
Claire Torchet1, Cecile Bousquet-Antonelli, Laura Milligan
1Wellcome Trust Centre for Cell Biology, University of Edinburgh, EH9 3JR Edinburgh, Scotland, UK.
Molecular Cell
|June 28, 2002
Summary
Mutations in RNA14 and RNA15 disrupt mRNA processing. The exosome and RNA helicase Dob1p/Mtr4p stabilize read-through transcripts, while Rrp6p stabilizes functional mRNAs, with degradation favored on glucose.
Area of Science:
- Molecular Biology
- Gene Expression Regulation
- RNA Processing
Background:
- RNA processing, including 3' cleavage and polyadenylation, is crucial for gene expression.
- The exosome complex and associated factors like Rrp41p and Dob1p/Mtr4p play key roles in RNA degradation and processing.
- Nuclear-specific exosome components, such as Rrp6p, have distinct functions in RNA metabolism.
Purpose of the Study:
- To investigate the roles of RNA14, RNA15, Rrp41p, Dob1p/Mtr4p, and Rrp6p in pre-mRNA processing and stability.
- To elucidate the mechanisms regulating the balance between degradation and processing of pre-mRNAs.
- To understand how cellular conditions, like glucose availability, influence these regulatory pathways.
Main Methods:
- Analysis of yeast strains with specific mutations (rna14.1, rna15.2).
- Depletion of key proteins (Rrp41p, Dob1p/Mtr4p, Rrp6p) using conditional expression systems.
- Assessment of pre-mRNA stability, polyadenylation status, and functionality for translation.
- Investigation of the impact of media composition (glucose) on RNA processing outcomes.
Main Results:
- Strains with rna14.1 and rna15.2 mutations exhibit defects in pre-mRNA 3' cleavage, polyadenylation, and transcription termination.
- Depletion of Rrp41p or Dob1p/Mtr4p stabilizes long, read-through transcripts in these mutant strains.
- Absence of Rrp6p in rna14.1 strains leads to stabilization of short, polyadenylated, and translatable pre-mRNAs.
- These Rrp6p-dependent mRNAs are products of exosome processing followed by uncoupled polyadenylation and their production is suppressed by Rrp41p depletion.
- Degradation of 3'-unprocessed pre-mRNAs is favored under glucose-rich conditions.
Conclusions:
- RNA14 and RNA15 are essential for proper pre-mRNA 3' end formation and transcription termination.
- The exosome complex (Rrp41p) and RNA helicase (Dob1p/Mtr4p) are involved in degrading aberrant transcripts.
- Rrp6p plays a critical role in processing and stabilizing functional mRNAs, potentially through a pathway distinct from complete degradation.
- A regulatory balance exists between RNA degradation and processing to functional mRNA, influenced by environmental cues like glucose availability.