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Published on: December 13, 2014
Nonsense-Mediated mRNA Decay: Degradation of Defective Transcripts Is Only Part of the Story
1Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, Massachusetts 01655; email: feng.he@umassmed.edu , allan.jacobson@umassmed.edu.
Abstract:
Nonsense-mediated mRNA decay (NMD) is a eukaryotic surveillance mechanism that monitors cytoplasmic mRNA translation and targets mRNAs undergoing premature translation termination for rapid degradation. From yeasts to humans, activation of NMD requires the function of the three conserved Upf factors: Upf1, Upf2, and Upf3. Here, we summarize the progress in our understanding of the molecular mechanisms of NMD in several model systems and discuss recent experiments that address the roles of Upf1, the principal regulator of NMD, in the initial targeting and final degradation of NMD-susceptible mRNAs. We propose a unified model for NMD in which the Upf factors provide several functions during premature termination, including the stimulation of release factor activity and the dissociation and recycling of ribosomal subunits. In this model, the ultimate degradation of the mRNA is the last step in a complex premature termination process.
Insights
Nonsense-mediated mRNA decay (NMD) uses Upf factors to degrade faulty mRNAs with premature stop codons. This process involves Upf1 in targeting and degradation, ensuring cellular quality control.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- Nonsense-mediated mRNA decay (NMD) is a crucial eukaryotic surveillance pathway.
- It targets mRNAs with premature termination codons (PTCs) for degradation.
- The conserved Upf1, Upf2, and Upf3 proteins are essential for NMD activation.
Purpose of the Study:
- To review the molecular mechanisms of NMD across various model systems.
- To discuss the role of Upf1 in targeting and degrading NMD-susceptible mRNAs.
- To propose a unified model for the NMD pathway.
Main Methods:
- Literature review of NMD mechanisms.
- Analysis of experimental data on Upf1 function.
- Synthesis of findings into a mechanistic model.
Main Results:
- Upf factors are conserved and essential for NMD.
- Upf1 plays a central role in both initial mRNA targeting and final degradation.
- NMD involves stimulation of release factor activity and ribosomal subunit recycling.
Conclusions:
- A unified model for NMD is proposed.
- Upf factors facilitate multiple steps in premature termination and mRNA degradation.
- mRNA degradation is the final step in a complex premature termination process.
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