Clarifying the translational pausing landscape in bacteria by ribosome profiling
Ontology highlight
ABSTRACT:
ORGANISM(S): Escherichia coli str. K-12 substr. MG1655
SUBMITTER: Allen Buskirk
PROVIDER: E-GEOD-72899 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
Similar Datasets
Project description:The rate of protein synthesis varies according to the mRNA sequence in ways that affect gene expression. Global analysis of translational pausing is now possible with ribosome profiling. Here, we revisit an earlier report that Shine-Dalgarno sequences are the major determinant of translational pausing in bacteria. Using refinements in the profiling method as well as biochemical assays, we find that SD motifs have little (if any) effect on elongation rates. We argue that earlier evidence of pausing arose from two factors. First, in previous analyses, pauses at Gly codons were difficult to distinguish from pauses at SD motifs. Second, and more importantly, the initial study preferentially isolated long ribosome-protected mRNA fragments that are enriched in SD motifs. These findings clarify the landscape of translational pausing in bacteria as observed by ribosome profiling.
2016-01-13 | GSE72899 | GEO
Project description:Recent studies have revealed that the mRNA translation is punctuated by ribosomal pauses through the body of transcripts. However, little is known about its physiological significance and regulatory aspects. Here we present a multi-dimensional ribosome profiling approach to quantify the dynamics of initiation and elongation of 80S ribosomes across the entire transcriptome in mammalian cells. We show that a subset of transcripts have a significant pausing of 80S ribosome around the start codon, creating a major barrier to the commitment of translation elongation. Intriguingly, genes encoding ribosome proteins themselves exhibit an exceptionally high initiation pausing on their transcripts. Our studies also reveal that the initiation pausing is dependent on the 5M-bM-^@M-^Y untranslated region (5M-bM-^@M-^Y UTR) of mRNAs and subject to the regulation of mammalian target of rapamycin complex 1 (mTORC1). Thus, the initiation pausing of 80S ribosome represents a novel regulatory step in translational control mediated by nutrient signaling pathway. Monitor the translational status of transcriptome in mammalian cells under different conditions
2011-11-12 | E-GEOD-25626 | biostudies-arrayexpress
Project description:Protein synthesis by ribosomes takes place on a linear substrate but at variable speeds. Transient pausing of ribosomes can impact a variety of co-translational processes, including protein targeting and folding. These pauses are influenced by the sequence of the mRNA. Thus redundancy in the genetic code allows the same protein to be translated at different rates. However, our knowledge of both the position and the mechanism of translational pausing in vivo is highly limited. Here we present a genome-wide analysis of translational pausing in bacteria using ribosome profiling-deep sequencing of ribosome-protected mRNA fragments. This approach enables high-resolution measurement of ribosome density profiles along most transcripts at unperturbed, endogenous expression levels. Unexpectedly, we found that codons decoded by rare tRNAs do not lead to slow translation under nutrient-rich conditions. Instead, Shine-Dalgarno-(SD) like features within coding sequences cause pervasive translational pausing. Using an orthogonal ribosome possessing an altered anti-SD sequence, we demonstrated that pausing is due to hybridization between mRNA and the 16S rRNA of the translating ribosome. In protein coding sequences, internal SD sequences are disfavoured, which leads to biased usage, avoiding codons and codon pairs that resemble canonical SD sites. Our results indicate that internal SD-like sequences are a major determinant of translation rates and a global driving force for the coding of bacterial genomes. Identification of translation pause sites in vivo using ribosome profiling
2012-04-01 | E-GEOD-35641 | biostudies-arrayexpress
Project description:Ribosome profiling is a powerful method for globally assessing the activity of ribosomes in a cell. Despite its application in many organisms, ribosome profiling studies in bacteria have struggled to obtain the resolution necessary to precisely define translational pauses. Here we report improvements that yield much higher resolution in E. coli profiling data, enabling us to more accurately assess ribosome pausing and refine earlier studies of the impact of polyproline motifs on elongation. We comprehensively characterize pausing at proline-rich motifs in the absence of elongation factor EFP. We find that only a small fraction of genes with strong pausing motifs have reduced ribosome density downstream and identify features that explain this phenomenon. These features allow us to predict which proteins likely have reduced output in the efp knockout strain. Ribosome profiling of E. coli MG1655 and mutants lacking EFP or its three modifiying enzymes
2015-03-10 | E-GEOD-64488 | biostudies-arrayexpress
Project description:DEAD-box RNA helicases eIF4A and Ded1 are believed to promote translation initiation by resolving mRNA secondary structures that impede ribosome attachment at the mRNA 5’ end or subsequent scanning of the 5’UTR, but whether they perform distinct functions or act redundantly in vivo is poorly understood. We compared the effects of mutations in Ded1 or eIF4A on global translational efficiencies (TEs) in yeast by ribosome footprint profiling. Despite similar reductions in bulk translation, inactivation of a cold-sensitive Ded1 mutant substantially reduced the TEs of >600 mRNAs, whereas inactivation of a temperature-sensitive eIF4A mutant yielded <40 similarly impaired mRNAs. The broader requirement for Ded1 did not reflect more pervasive secondary structures at low temperature, as inactivation of temperature-sensitive and cold-sensitive ded1 mutants gave highly correlated results. Interestingly, Ded1-dependent mRNAs exhibit greater than average 5’UTR length and propensity for secondary structure, implicating Ded1 in scanning though structured 5' UTRs. Reporter assays confirmed that cap- distal stem-loop insertions increase dependence on Ded1 but not eIF4A for efficient translation. While only a small fraction of mRNAs is strongly dependent on eIF4A, this dependence is significantly correlated with requirements for Ded1 and 5’UTR features characteristic of Ded1- dependent mRNAs. Our findings suggest that Ded1 is critically required to promote scanning through secondary structures within 5’UTRs; and while eIF4A cooperates with Ded1 in this function, it also promotes a step of initiation common to virtually all yeast mRNAs. We compared the effects of mutations in Ded1 or eIF4A on global translational efficiencies (TEs) in yeast by ribosome footprint profiling.The study includes 32 samples, comprised of 16 mRNA-Seq samples and 16 ribosome footprint profiling samples, derived from biological replicates of 3 mutant strains, ded1-cs, ded1-ts and tif1-ts, and the corresponding wild-type strains. The tif1-ts mutant and its wild-type counterpart were analyzed at 30°C and 37°C.
2015-03-02 | E-GEOD-66411 | biostudies-arrayexpress
Project description:Protein synthesis by ribosomes takes place on a linear substrate but at variable speeds. Transient pausing of ribosomes can impact a variety of co-translational processes, including protein targeting and folding. These pauses are influenced by the sequence of the mRNA. Thus redundancy in the genetic code allows the same protein to be translated at different rates. However, our knowledge of both the position and the mechanism of translational pausing in vivo is highly limited. Here we present a genome-wide analysis of translational pausing in bacteria using ribosome profiling-deep sequencing of ribosome-protected mRNA fragments. This approach enables high-resolution measurement of ribosome density profiles along most transcripts at unperturbed, endogenous expression levels. Unexpectedly, we found that codons decoded by rare tRNAs do not lead to slow translation under nutrient-rich conditions. Instead, Shine-Dalgarno-(SD) like features within coding sequences cause pervasive translational pausing. Using an orthogonal ribosome possessing an altered anti-SD sequence, we demonstrated that pausing is due to hybridization between mRNA and the 16S rRNA of the translating ribosome. In protein coding sequences, internal SD sequences are disfavoured, which leads to biased usage, avoiding codons and codon pairs that resemble canonical SD sites. Our results indicate that internal SD-like sequences are a major determinant of translation rates and a global driving force for the coding of bacterial genomes.
2012-04-01 | GSE35641 | GEO
Project description:Ribosome profiling is a powerful method for globally assessing the activity of ribosomes in a cell. Despite its application in many organisms, ribosome profiling studies in bacteria have struggled to obtain the resolution necessary to precisely define translational pauses. Here we report improvements that yield much higher resolution in E. coli profiling data, enabling us to more accurately assess ribosome pausing and refine earlier studies of the impact of polyproline motifs on elongation. We comprehensively characterize pausing at proline-rich motifs in the absence of elongation factor EFP. We find that only a small fraction of genes with strong pausing motifs have reduced ribosome density downstream and identify features that explain this phenomenon. These features allow us to predict which proteins likely have reduced output in the efp knockout strain.
2015-03-10 | GSE64488 | GEO
Project description:The regulation of translation elongation plays a vital role in protein folding; an adequate translational pause provides time and cellular environments for the co-translational folding of nascent peptides. However, the genomic landscape, sequence determinants, and molecular consequences of translational pausing remain mostly unknown. In this study, we performed disome-seq that sequenced mRNA fragments protected by two consecutive ribosomes – a product of severe translational pauses during which the upstream ribosome collides into the paused one. We detected severe translational pauses on ~75% of yeast genes. These pauses were often explained by one of the three mechanisms: 1) slow ribosome releasing at stop codons, 2) slow peptide formation from proline, glycine, asparagine, and cysteine, and 3) slow leaving of polylysine from the exit tunnel of ribosomes. Notably, these amino acids also terminate the α-helical conformation. Such dual roles of amino acids establish an inborn coupling between the synthetic completion of a structural motif and a translational pause. Furthermore, paused ribosomes often recruit chaperones to assist protein folding. As a consequence, emergent protein structures during evolution should be ready to be correctly folded. Collectively, our study shows widespread translational pauses and sheds lights on a better understanding of the regulation of co-translational protein folding.
2020-12-10 | PXD015271 | Pride
Project description:Recent studies have revealed that the mRNA translation is punctuated by ribosomal pauses through the body of transcripts. However, little is known about its physiological significance and regulatory aspects. Here we present a multi-dimensional ribosome profiling approach to quantify the dynamics of initiation and elongation of 80S ribosomes across the entire transcriptome in mammalian cells. We show that a subset of transcripts have a significant pausing of 80S ribosome around the start codon, creating a major barrier to the commitment of translation elongation. Intriguingly, genes encoding ribosome proteins themselves exhibit an exceptionally high initiation pausing on their transcripts. Our studies also reveal that the initiation pausing is dependent on the 5’ untranslated region (5’ UTR) of mRNAs and subject to the regulation of mammalian target of rapamycin complex 1 (mTORC1). Thus, the initiation pausing of 80S ribosome represents a novel regulatory step in translational control mediated by nutrient signaling pathway. Untreated TSC2 WT MEFs, TSC2 KO MEFs and TSC2 WT MEFs, TSC2 KO MEFs treated with 20nM rapamycin for 30 minutes or 3hours were harvested for ribosme profiling. The fraction samples were pooled into three groups based on velocity sedimentation: single ribosome fraction (Small group), fractions with 2 ~ 4 ribosomes (Medium group), and the one with ≥5 ribosomes (Large group). RNA were extracted from the whole cell lysis and each fraction group.
2011-11-12 | E-GEOD-25331 | biostudies-arrayexpress
Project description:The molecular mechanisms of ethanol toxicity and tolerance in bacteria, while important for biotechnology and bioenergy applications, remain incompletely understood. Genetic studies have identified potential cellular targets for ethanol and revealed multiple mechanisms of tolerance, but it remains difficult to separate direct and indirect effects of ethanol. We used adaptive evolution to generate spontaneous ethanol-tolerant strains of Escherichia coli, then characterized the mechanisms of toxicity and resistance associated with select mutations. Evolved alleles of metJ, rho, and rpsQ were sufficient to recapitulate much of the observed ethanol tolerance, implicating translation and transcription as key processes affected by ethanol. We found that ethanol induces mistranslation errors during protein synthesis, and that the evolved rpsQ allele protects cells by rendering the ribosome hyper-accurate. Ribosome profiling and RNAseq analyses of the ethanol-tolerant strain versus the wild type established that ethanol negatively affects transcriptional and translational processivity. Ethanol-stressed cells exhibited ribosomal stalling at internal AUG codons, which may be ameliorated by the adaptive inactivation of the MetJ repressor of methionine biosynthesis genes. Ethanol also caused aberrant intragenic transcription termination for mRNAs with low ribosome density, which was reduced in a strain with the adaptive rho mutation. Furthermore, ethanol inhibited transcript elongation by RNA polymerase in vitro. We propose that ethanol-induced inhibition and uncoupling of mRNA and protein synthesis are major contributors to ethanol toxicity in E. coli, and that adaptive mutations in metJ, rho, and rpsQ protect central dogma processes in the presence of ethanol. Examination of wild-type and mutant strains at three different time points (one pre-ethanol-stress, two post-ethanol-stress)
2014-06-18 | E-GEOD-56372 | biostudies-arrayexpress