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[Protein Synthesis, Post-Translational Modification, and Degradation] Functional Analysis of the Interplay between Translation Termination, Selenocysteine Codon Context, and Selenocysteine Insertion Sequence-binding Protein 2

[Protein Synthesis, Post-Translational Modification, and Degradation] Functional Analysis of the Interplay between Translation Termination, Selenocysteine Codon Context, and Selenocysteine Insertion Sequence-binding Protein 2 - Science News and Views

[Protein Synthesis, Post-Translational Modification, and Degradation] Functional Analysis of the Interplay between Translation Termination, Selenocysteine Codon Context, and Selenocysteine Insertion Sequence-binding Protein 2 - The latest news and publications from Nature, Science, Cell and other journals. Post science topics and your thoughts here. Anything science related goes here.


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Old 12-14-2007, 02:47 PM
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Default [Protein Synthesis, Post-Translational Modification, and Degradation] Functional Analysis of the Interplay between Translation Termination, Selenocysteine Codon Context, and Selenocysteine Insertion Sequence-binding Protein 2



[Protein Synthesis, Post-Translational Modification, and Degradation] Functional Analysis of the Interplay between Translation Termination, Selenocysteine Codon Context, and Selenocysteine Insertion Sequence-binding Protein 2

A selenocysteine insertion sequence (SECIS) element in the 3'-untranslated region and an in-frame UGA codon are the requisite cis-acting elements for the incorporation of selenocysteine into selenoproteins. Equally important are the trans-acting factors SBP2, Sec-tRNA[Ser]Sec, and eEFSec. Multiple in-frame UGAs and two SECIS elements make the mRNA encoding selenoprotein P (Sel P) unique. To study the role of codon context in determining the efficiency of UGA readthrough at each of the 10 rat Sel P Sec codons, we individually cloned 27-nucleotide-long fragments representing each UGA codon context into a luciferase reporter construct harboring both Sel P SECIS elements. Significant differences, spanning an 8-fold range of UGA readthrough efficiency, were observed, but these differences were dramatically reduced in the presence of excess SBP2. Mutational analysis of the "fourth base" of contexts 1 and 5 revealed that only the latter followed the established rules for hierarchy of translation termination. In addition, mutations in either or both of the Sel P SECIS elements resulted in differential effects on UGA readthrough. Interestingly, even when both SECIS elements harbored a mutation of the core region required for Sec incorporation, context 5 retained a significantly higher level of readthrough than context 1. We also show that SBP2-dependent Sec incorporation is able to repress G418-induced UGA readthrough as well as eRF1-induced stimulation of termination. We conclude that a large codon context forms a cis-element that works together with Sec incorporation factors to determine readthrough efficiency.
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analysis , codon , context , degradation , functional , insertion , interplay , modification , posttranslational , protein , selenocysteine , sequencebinding , synthesis , termination , translation


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