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.
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.
|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|
|Roy, Bijoyita; Jacobson, Allan (2013) The intimate relationships of mRNA decay and translation. Trends Genet 29:691-9|
|He, Feng; Ganesan, Robin; Jacobson, Allan (2013) Intra- and intermolecular regulatory interactions in Upf1, the RNA helicase central to nonsense-mediated mRNA decay in yeast. Mol Cell Biol 33:4672-84|
|Min, Ei Ei; Roy, Bijoyita; Amrani, Nadia et al. (2013) Yeast Upf1 CH domain interacts with Rps26 of the 40S ribosomal subunit. RNA 19:1105-15|
|Peltz, Stuart W; Morsy, Manal; Welch, Ellen M et al. (2013) Ataluren as an agent for therapeutic nonsense suppression. Annu Rev Med 64:407-25|
|Kervestin, Stephanie; Li, Chunfang; Buckingham, Richard et al. (2012) Testing the faux-UTR model for NMD: analysis of Upf1p and Pab1p competition for binding to eRF3/Sup35p. Biochimie 94:1560-71|
|Ghosh, Shubhendu; Jacobson, Allan (2010) RNA decay modulates gene expression and controls its fidelity. Wiley Interdiscip Rev RNA 1:351-61|
|Dong, Shuyun; Jacobson, Allan; He, Feng (2010) Degradation of YRA1 Pre-mRNA in the cytoplasm requires translational repression, multiple modular intronic elements, Edc3p, and Mex67p. PLoS Biol 8:e1000360|
|Amrani, Nadia; Ghosh, Shubhendu; Mangus, David A et al. (2008) Translation factors promote the formation of two states of the closed-loop mRNP. Nature 453:1276-80|
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