My long-term goal is an understanding of the molecular mechanisms that regulate nonsense-mediated mRNA decay (NMD) in the the yeast Saccharomyces cerevisiae. Our recent experiments have led us to formulate the faux UTR model for NMD in yeast, and independent studies in higher organisms have provided Strong support for the general applicability of this model to all eukaryotes. Our data Indicate that premature and normal termination differ mechanistically, with premature termination being a relatively inefficient process that leads to the ribosomal recruitment of at least three key proteins (Upf1, Upf2yNmd2, and Upf3). These factors subsequently function in the dissociation of the premature termination complex and in the recruitment ofthe decapping enzyme responsible for initiating decay ofthe transcript. In the experiments of this proposal, we will define the critical Interactions underlying these observations and elucidate the mechanisms by which ribosomes are recycled subsequent to premature and normal termination, and by which decapping of NMD substrates is triggered. With the goal of further testing the faux UTR model for NMD, I plan to: a) define the timing and interaction-dependencies of Upf1, Upf2/Nmd2, and Upf3 association with prematurely terminating ribosomes, b) delineate the protein:protein interactions that link the decapping enzyme to the UPF/NMD factors, c) evaluate the regulatory role of ribosome recycling in cis subsequent to normal or premature termination, and d) characterize the Upf1 activity that dissociates and/or remodels ribosomal subunits at premature termination codons.

Public Health Relevance

Nonsense mutations promote premature translational termination and cause anywhere from 5 to 70% of the individual cases of most inherited diseases. The UAG, UAA, and UGA codons that they encode in mRNA trigger NMD, a surveillance mechanism which ensures that nonsense-containing mRNAs are degraded rapidly, thereby preventing the accumulation of polypeptide fragments potentially toxic to the cell.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Method to Extend Research in Time (MERIT) Award (R37)
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Special Emphasis Panel (NSS)
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Bender, Michael T
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University of Massachusetts Medical School Worcester
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Jacobson, Allan (2017) The moment when translational control had a theory of everything. Nat Rev Mol Cell Biol 18:344
Roy, Bijoyita; Friesen, Westley J; Tomizawa, Yuki et al. (2016) Ataluren stimulates ribosomal selection of near-cognate tRNAs to promote nonsense suppression. Proc Natl Acad Sci U S A 113:12508-12513
Dong, Shuyun; Jacobson, Allan; He, Feng (2016) Correction: Degradation of YRA1 Pre-mRNA in the Cytoplasm Requires Translational Repression, Multiple Modular Intronic Elements, Edc3p, and Mex67p. PLoS Biol 14:e1002470
He, Feng; Jacobson, Allan (2015) Nonsense-Mediated mRNA Decay: Degradation of Defective Transcripts Is Only Part of the Story. Annu Rev Genet 49:339-66
Jacobson, Allan (2015) Methods to our madness. RNA 21:529-30
Celik, Alper; Kervestin, Stephanie; Jacobson, Allan (2015) NMD: At the crossroads between translation termination and ribosome recycling. Biochimie 114:2-9
Roy, Bijoyita; Leszyk, John D; Mangus, David A et al. (2015) Nonsense suppression by near-cognate tRNAs employs alternative base pairing at codon positions 1 and 3. Proc Natl Acad Sci U S A 112:3038-43
He, Feng; Jacobson, Allan (2015) Control of mRNA decapping by positive and negative regulatory elements in the Dcp2 C-terminal domain. RNA 21:1633-47
He, Feng; Li, Chunfang; Roy, Bijoyita et al. (2014) Yeast Edc3 targets RPS28B mRNA for decapping by binding to a 3' untranslated region decay-inducing regulatory element. Mol Cell Biol 34:1438-51
Tsanova, Borislava; Spatrick, Phyllis; Jacobson, Allan et al. (2014) The RNA exosome affects iron response and sensitivity to oxidative stress. RNA 20:1057-67

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