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Degradation of most yeast mRNAs involves decapping by Dcp1/Dcp2. DEAD-box protein Dhh1 has been implicated as an activator of decapping, in coupling codon non-optimality to enhanced degradation, and as a translational repressor, but its functions in cells are incompletely understood. RNA-Seq analyses coupled with CAGE sequencing of all capped mRNAs revealed increased abundance of hundreds of mRNAs indcp2Δ cells that appears to result directly from impaired decapping rather than elevated transcription. Interestingly, only a subset of mRNAs requires Dhh1 for targeting by Dcp2, and also generally requires the other decapping activators Pat1, Edc3, or Scd6; whereas most of the remaining transcripts utilize nonsense-mediated mRNA decay factors for Dcp2-mediated turnover. Neither inefficient translation initiation nor stalled elongation appears to be a major driver of Dhh1-enhanced mRNA degradation. Surprisingly, ribosome profiling revealed thatdcp2Δ confers widespread changes in relative translational efficiencies (TEs) that generally favor well-translated mRNAs. Because ribosome biogenesis is reduced while capped mRNA abundance is increased bydcp2Δ,we propose that an increased ratio of mRNA to ribosomes increases competition among mRNAs for limiting ribosomes to favor efficiently translated mRNAs indcp2Δ cells. Interestingly, genes involved in respiration or utilization of alternative carbon or nitrogen sources are upregulated, and both mitochondrial function and cell filamentation are elevated indcp2Δ cells, suggesting that decapping sculpts gene expression post-transcriptionally to fine-tune metabolic pathways and morphological transitions according to nutrient availability.
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Programmable initiation of mRNA translation by trans-RNA
Several approaches exist to silence genes, but few tools are available to activate individual mRNAs for translation inside cells. Guiding ribosomes to specific start codons without altering the original sequence remains a formidable task. Here we design capped trans-RNAs capable of directing ribosomes to specific initiation sites on individual mRNAs when the trans-cap is positioned near the target start codon. Structural and biochemical data suggest that the capped trans-RNA facilitates ribosome loading and scanning on the target mRNA through a synergistic mechanism involving alternative cap recognition. The trans-RNA also acts independently of the cap on the target mRNA, enabling translation of circular RNAs lacking internal ribosome entry sites. We apply trans-RNAs in vivo to achieve programmable alternative translation of endogenous genes in mouse liver. Finally, we provide the evidence for the existence of natural transcripts that, similarly to exogenous trans-RNAs, activate translation of endogenous mRNAs.
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- Award ID(s):
- 2226633
- PAR ID:
- 10673417
- Publisher / Repository:
- Nature Biotechnology
- Date Published:
- Journal Name:
- Nature Biotechnology
- ISSN:
- 1087-0156
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1038/s41587-025-02897-1
