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).
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.
Project description:Ribosomes undergo substantial conformational changes during translation elongation to accommodate incoming aminoacyl-tRNAs and translocate along the mRNA template. We used multiple elongation inhibitors and chemical probing to define ribosome conformational states corresponding to different sized ribosome-protected mRNA fragments (RPFs) generated by ribosome profiling. We show using various genetic and environmental perturbations that the previously identified 20-22 nucleotide (nt) RPFs correspond predominantly to ribosomes in a pre-accommodation state with an open 40S ribosomal A site while the classical 27-29 nt fragments correspond to ribosomes in a pre-translocation state with an occupied 40S ribosomal A site. These distinct ribosome conformational states revealed by ribosome profiling are seen in all eukaryotes tested including fungi, worms and mammals. This high-resolution ribosome profiling approach reveals the anticipated Rck2-dependent inhibition of translocation through eEF2 phosphorylation during hyperosmotic stress. These same approaches reveal a strong translation elongation arrest during oxidative stress where the ribosomes are trapped in a pre-translocation state, but in this case the translational arrest is independent of Rck2-driven eEF2 phosphorylation. These results provide new insights and approaches for defining the molecular events that impact translation elongation throughout biology.
Project description:Ribosomes undergo substantial conformational changes during translation elongation to accommodate incoming aminoacyl-tRNAs and translocate along the mRNA template. We used multiple elongation inhibitors and chemical probing to define ribosome conformational states corresponding to different sized ribosome-protected mRNA fragments (RPFs) generated by ribosome profiling. We show using various genetic and environmental perturbations that the previously identified 20-22 nucleotide (nt) RPFs correspond predominantly to ribosomes in a pre-accommodation state with an open 40S ribosomal A site while the classical 27-29 nt fragments correspond to ribosomes in a pre-translocation state with an occupied 40S ribosomal A site. These distinct ribosome conformational states revealed by ribosome profiling are seen in all eukaryotes tested including fungi, worms and mammals. This high-resolution ribosome profiling approach reveals the anticipated Rck2-dependent inhibition of translocation through eEF2 phosphorylation during hyperosmotic stress. These same approaches reveal a strong translation elongation arrest during oxidative stress where the ribosomes are trapped in a pre-translocation state, but in this case the translational arrest is independent of Rck2-driven eEF2 phosphorylation. These results provide new insights and approaches for defining the molecular events that impact translation elongation throughout biology.
Project description:Ribosomes undergo substantial conformational changes during translation elongation to accommodate incoming aminoacyl-tRNAs and translocate along the mRNA template. We used multiple elongation inhibitors and chemical probing to define ribosome conformational states corresponding to different sized ribosome-protected mRNA fragments (RPFs) generated by ribosome profiling. We show using various genetic and environmental perturbations that the previously identified 20-22 nucleotide (nt) RPFs correspond predominantly to ribosomes in a pre-accommodation state with an open 40S ribosomal A site while the classical 27-29 nt fragments correspond to ribosomes in a pre-translocation state with an occupied 40S ribosomal A site. These distinct ribosome conformational states revealed by ribosome profiling are seen in all eukaryotes tested including fungi, worms and mammals. This high-resolution ribosome profiling approach reveals the anticipated Rck2-dependent inhibition of translocation through eEF2 phosphorylation during hyperosmotic stress. These same approaches reveal a strong translation elongation arrest during oxidative stress where the ribosomes are trapped in a pre-translocation state, but in this case the translational arrest is independent of Rck2-driven eEF2 phosphorylation. These results provide new insights and approaches for defining the molecular events that impact translation elongation throughout biology.
Project description:Ribosomes undergo substantial conformational changes during translation elongation to accommodate incoming aminoacyl-tRNAs and translocate along the mRNA template. We used multiple elongation inhibitors and chemical probing to define ribosome conformational states corresponding to different sized ribosome-protected mRNA fragments (RPFs) generated by ribosome profiling. We show using various genetic and environmental perturbations that the previously identified 20-22 nucleotide (nt) RPFs correspond predominantly to ribosomes in a pre-accommodation state with an open 40S ribosomal A site while the classical 27-29 nt fragments correspond to ribosomes in a pre-translocation state with an occupied 40S ribosomal A site. These distinct ribosome conformational states revealed by ribosome profiling are seen in all eukaryotes tested including fungi, worms and mammals. This high-resolution ribosome profiling approach reveals the anticipated Rck2-dependent inhibition of translocation through eEF2 phosphorylation during hyperosmotic stress. These same approaches reveal a strong translation elongation arrest during oxidative stress where the ribosomes are trapped in a pre-translocation state, but in this case the translational arrest is independent of Rck2-driven eEF2 phosphorylation. These results provide new insights and approaches for defining the molecular events that impact translation elongation throughout biology.
Project description:Techniques for systematically monitoring protein translation have lagged far behind methods for measuring mRNA levels. Here we present a ribosome profiling strategy, based on deep sequencing of ribosome protected mRNA fragments, that enables genome-wide investigation of translation with sub-codon resolution. We used this technique to monitor translation in budding yeast under both rich and starvation conditions. These studies defined the protein sequences being translated and found extensive translational control both for determining absolute protein abundance and for responding to environmental stress. We also observed distinct phases during translation involving a large decrease in ribosome density going from early to late peptide elongation as well as wide-spread, regulated initiation at non-AUG codons. Ribosome profiling is readily adaptable to other organisms, making high-precision investigation of protein translation experimentally accessible. Examine replicates of ribosome footprints and mRNA abundance in biological replicates of log-phase growth and acute amino acid starvation
Project description:Techniques for systematically monitoring protein translation have lagged far behind methods for measuring mRNA levels. Here we present a ribosome profiling strategy, based on deep sequencing of ribosome protected mRNA fragments, that enables genome-wide investigation of translation with sub-codon resolution. We used this technique to monitor translation in budding yeast under both rich and starvation conditions. These studies defined the protein sequences being translated and found extensive translational control both for determining absolute protein abundance and for responding to environmental stress. We also observed distinct phases during translation involving a large decrease in ribosome density going from early to late peptide elongation as well as wide-spread, regulated initiation at non-AUG codons. Ribosome profiling is readily adaptable to other organisms, making high-precision investigation of protein translation experimentally accessible.
Project description:The ability to sequence genomes has far outstripped approaches for deciphering the information they encode. Here we present a suite of techniques, based on ribosome profiling (the deep-sequencing of ribosome-protected mRNA fragments), to provide genome-wide maps of protein synthesis as well as a pulse-chase strategy for determining rates of translation elongation. We exploit the propensity of harringtonine to cause ribosomes to accumulate at sites of translation initiation together with a machine learning algorithm to define protein products systematically. Analysis of translation in mouse embryonic stem cells reveals thousands of strong pause sites and novel translation products. These include amino-terminal extensions and truncations and upstream open reading frames with regulatory potential, initiated at both AUG and non-AUG codons, whose translation changes after differentiation. We also define a new class of short, polycistronic ribosome-associated coding RNAs (sprcRNAs) that encode small proteins. Our studies reveal an unanticipated complexity to mammalian proteomes. Examination of translation in mouse embryonic stem cells and during differentiation into embryoid bodies
Project description:Ribosome profiling performed on interspecific hybrids of Sacharromyces cerevisiae and S. paradoxus in order to identify allele-specific expression indicative of cis-regulatory divergence at the level of mRNA abundance and protein translation. Two biological replicate libraries sequenced from ribosome protected fragments as well as poly-A-selected mRNA of hybrids in addition to one biological replicate library of poly-A selected mRNA from each parental strain.