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Distinct stages of the translation elongation cycle revealed by sequencing ribosome-protected mRNA fragments

ABSTRACT: During translation elongation, the ribosome ratchets along its mRNA template, incorporating each new amino acid and translocating from one codon to the next. The elongation cycle requires dramatic structural rearrangements of the ribosome. We show here that deep sequencing of ribosome-protected mRNA fragments reveals not only the position of each ribosome but also, unexpectedly, its particular stage of the elongation cycle. Sequencing reveals two distinct populations of ribosome footprints, 28-30 nucleotides and 20-22 nucleotides long, representing translating ribosomes in distinct states, differentially stabilized by specific elongation inhibitors. We find that the balance of small and large footprints varies by codon and is correlated with translation speed. The ability to visualize conformational changes in the ribosome during elongation, at single-codon resolution, provides a new way to study the detailed kinetics of translation and a new probe with which to identify the factors that affect each step in the elongation cycle.

ORGANISM(S): Saccharomyces cerevisiae

PROVIDER: GSE58321 | GEO | 2014/06/10

SECONDARY ACCESSION(S): PRJNA251988

REPOSITORIES: GEO

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Distinct stages of the translation elongation cycle revealed by sequencing ribosome-protected mRNA fragments

Project description:During translation elongation, the ribosome ratchets along its mRNA template, incorporating each new amino acid and translocating from one codon to the next. The elongation cycle requires dramatic structural rearrangements of the ribosome. We show here that deep sequencing of ribosome-protected mRNA fragments reveals not only the position of each ribosome but also, unexpectedly, its particular stage of the elongation cycle. Sequencing reveals two distinct populations of ribosome footprints, 28-30 nucleotides and 20-22 nucleotides long, representing translating ribosomes in distinct states, differentially stabilized by specific elongation inhibitors. We find that the balance of small and large footprints varies by codon and is correlated with translation speed. The ability to visualize conformational changes in the ribosome during elongation, at single-codon resolution, provides a new way to study the detailed kinetics of translation and a new probe with which to identify the factors that affect each step in the elongation cycle. Ribosome profiling, or sequencing of ribosome-protected mRNA fragments, in yeast. We assay ribosome footprint sizes and positions in three conditions: untreated yeast (3 replicates) and yeast treated with translation inhibitors cycloheximide (2 replicates) and anisomycin (2 biological replicates, one technical replicate). We also treat yeast with 3-aminotriazole to measure the effect of limited histidine tRNAs on ribosome footprint size and distribution (two treatment durations).

2014-06-10 | E-GEOD-58321 | biostudies-arrayexpress

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Protein synthesis rates and ribosome occupancies reveal determinants of translation elongation rates

Project description:Although protein synthesis dynamics has been studied both with theoretical models and by profiling ribosome footprints, the determinants of ribosome flux along open reading frames (ORFs) are not fully understood. Combining measurements of protein synthesis rate with ribosome footprinting data, we here inferred translation initiation and elongation rates for over a thousand ORFs in exponentially-growing wildtype yeast cells. We found that the amino acid composition of synthesized proteins is as important a determinant of translation elongation rate as parameters related to codon and tRNA adaptation. We did not find evidence of ribosome collisions curbing the protein output of yeast transcripts, either in high translation conditions associated with exponential growth, or in strains in which deletion of individual ribosomal protein genes leads to globally increased or decreased translation. Slow translation elongation is characteristic of RP-encoding transcripts, which have markedly lower protein output compared to other transcripts with equally high ribosome densities.

2019-09-10 | PXD014357 | Pride

Redefining the translational status of 80S monosomes

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Ribosome Profiling Reveals Pervasive Translation Outside of Annotated Protein-Coding Genes

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2014-08-21 | E-GEOD-60095 | biostudies-arrayexpress

Anatomy of footprint extension in ribosome profiling reveals translational landscape mediated by S1 protein in bacteria

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Project description:Protein translation depends on mRNA-specific initiation, elongation, and termination rates. While the regulation of ribosome elongation is well studied in bacteria and yeast, less is known in higher eukaryotes. Here, we combined ribosome and tRNA profiling to investigate the relations between ribosome elongation rates, (aminoacyl-) tRNA levels and codon usage in mammals. We modeled codon-specific ribosome dwell times and translation fluxes from ribosome profiling, considering pair-interactions between ribosome sites. In mouse liver, the model revealed site and codon specific dwell times, as well as codon pair-interactions clustering by amino acids. While translation fluxes varied significantly across diurnal time and feeding regimen, codon dwell times were highly stable, and conserved in human. Fasting had no effect on codon dwell times in mouse liver. Profiling of total and aminoacylated tRNAs revealed highly heterogeneous levels with specific isoacceptor patterns and a correlation with codon usage. tRNAs for isoleucine, asparagine, aspartate and arginine were lowly loaded and conserved in fasted mice. Finally, codons with low levels of charged tRNAs and high codon usage relative to tRNA abundance exhibited long dwell times. Together, these analyses pave the way towards understanding the complex relation between tRNA loading, codon usage and ribosome dwell times in mammals.

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