A systematically-revised ribosome profiling method for bacteria reveals pauses at single-codon resolution
- Johns Hopkins University School of Medicine, United States
Abstract
In eukaryotes, ribosome profiling provides insight into the mechanism of protein synthesis at the codon level. In bacteria, however, the method has been more problematic and no consensus has emerged for how to best prepare profiling samples. Here, we identify the sources of these problems and describe new solutions for arresting translation and harvesting cells in order to overcome them. These improvements remove confounding artifacts and improve the resolution to allow analyses of ribosome behavior at the codon level. With a clearer view of the translational landscape in vivo, we observe that filtering cultures leads to translational pauses at serine and glycine codons through the reduction of tRNA aminoacylation levels. This observation illustrates how bacterial ribosome profiling studies can yield insight into the mechanism of protein synthesis at the codon level and how these mechanisms are regulated in response to changes in the physiology of the cell.
Data availability
Sequencing data have been deposited in GEO under accession code GSE119104.
-
A systematically-revised ribosome profiling method for bacteria reveals pauses at single-codon resolutionNCBI Gene Expression Omnibus, GSE119104.
-
A streamlined ribosome profiling protocol for the characterization of microorganismsNCBI Gene Expression Omnibus, GSE63858.
-
High-resolution view of bacteriophage lambda gene expression by ribosome profilingNCBI Gene Expression Omnibus, GSE47509.
-
Selective ribosome profiling reveals the cotranslational chaperone action of trigger factor in vivoNCBI Gene Expression Omnibus, GSE33671.
-
Global analysis of translation termination in E. coliNCBI Gene Expression Omnibus, GSE88725.
-
The anti-Shine-Dalgarno sequence drives translational pausing and codon choice in bacteriaNCBI Gene Expression Omnibus, GSE35641.
-
An integrated approach reveals regulatory controls on bacterial translation elongationNCBI Gene Expression Omnibus, GSE51052.
-
Clarifying the Translational Pausing Landscape in Bacteria by Ribosome ProfilingNCBI Gene Expression Omnibus, GSE72899.
Article and author information
Author details
Funding
National Institute of General Medical Sciences (GM110113)
- Allen R Buskirk
Howard Hughes Medical Institute
- Rachel Green
National Institute of General Medical Sciences (GM105816)
- Allen R Buskirk
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2019, Mohammad et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
Metrics
-
- 17,272
- views
-
- 1,752
- downloads
-
- 176
- citations
Views, downloads and citations are aggregated across all versions of this paper published by eLife.
Download links
A two-part list of links to download the article, or parts of the article, in various formats.
Downloads (link to download the article as PDF)
Open citations (links to open the citations from this article in various online reference manager services)
Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)
A systematically-revised ribosome profiling method for bacteria reveals pauses at single-codon resolution
eLife 8:e42591.
https://doi.org/10.7554/eLife.42591
Further reading
-
- Biochemistry and Chemical Biology
Missense mutations in the amyloid precursor protein (APP) and presenilin-1 (PSEN1) cause early-onset familial Alzheimer’s disease (FAD) and alter proteolytic production of secreted 38-to-43-residue amyloid β-peptides (Aβ) by the PSEN1-containing γ-secretase complex, ostensibly supporting the amyloid hypothesis of pathogenesis. However, proteolysis of APP substrate by γ-secretase is processive, involving initial endoproteolysis to produce long Aβ peptides of 48 or 49 residues followed by carboxypeptidase trimming in mostly tripeptide increments. We recently reported evidence that FAD mutations in APP and PSEN1 cause deficiencies in early steps in processive proteolysis of APP substrate C99 and that this results from stalled γ-secretase enzyme-substrate and/or enzyme-intermediate complexes. These stalled complexes triggered synaptic degeneration in a Caenorhabditis elegans model of FAD independently of Aβ production. Here, we conducted full quantitative analysis of all proteolytic events on APP substrate by γ-secretase with six additional PSEN1 FAD mutations and found that all six are deficient in multiple processing steps. However, only one of these (F386S) was deficient in certain trimming steps but not in endoproteolysis. Fluorescence lifetime imaging microscopy in intact cells revealed that all six PSEN1 FAD mutations lead to stalled γ-secretase enzyme-substrate/intermediate complexes. The F386S mutation, however, does so only in Aβ-rich regions of the cells, not in C99-rich regions, consistent with the deficiencies of this mutant enzyme only in trimming of Aβ intermediates. These findings provide further evidence that FAD mutations lead to stalled and stabilized γ-secretase enzyme-substrate and/or enzyme-intermediate complexes and are consistent with the stalled process rather than the products of γ-secretase proteolysis as the pathogenic trigger.
-
- Biochemistry and Chemical Biology
- Chromosomes and Gene Expression
Hyperactive interferon (IFN) signaling is a hallmark of Down syndrome (DS), a condition caused by Trisomy 21 (T21); strategies that normalize IFN signaling could benefit this population. Mediator-associated kinases CDK8 and CDK19 drive inflammatory responses through incompletely understood mechanisms. Using sibling-matched cell lines with/without T21, we investigated Mediator kinase function in the context of hyperactive IFN in DS over a 75 min to 24 hr timeframe. Activation of IFN-response genes was suppressed in cells treated with the CDK8/CDK19 inhibitor cortistatin A (CA), via rapid suppression of IFN-responsive transcription factor (TF) activity. We also discovered that CDK8/CDK19 affect splicing, a novel means by which Mediator kinases control gene expression. To further probe Mediator kinase function, we completed cytokine screens and metabolomics experiments. Cytokines are master regulators of inflammatory responses; by screening 105 different cytokine proteins, we show that Mediator kinases help drive IFN-dependent cytokine responses at least in part through transcriptional regulation of cytokine genes and receptors. Metabolomics revealed that Mediator kinase inhibition altered core metabolic pathways in cell type-specific ways, and broad upregulation of anti-inflammatory lipid mediators occurred specifically in kinase-inhibited cells during hyperactive IFNγ signaling. A subset of these lipids (e.g. oleamide, desmosterol) serve as ligands for nuclear receptors PPAR and LXR, and activation of these receptors occurred specifically during hyperactive IFN signaling in CA-treated cells, revealing mechanistic links between Mediator kinases, lipid metabolism, and nuclear receptor function. Collectively, our results establish CDK8/CDK19 as context-specific metabolic regulators, and reveal that these kinases control gene expression not only via TFs, but also through metabolic changes and splicing. Moreover, we establish that Mediator kinase inhibition antagonizes IFN signaling through transcriptional, metabolic, and cytokine responses, with implications for DS and other chronic inflammatory conditions.
