Project description:Ribosome pausing slows down translation and can affect protein synthesis. Improving translation efficiency can therefore be of commercial value. Here, we investigated the occurrence of ribosome pausing during amylase secretion by the industrial production organism Bacillus subtilis under semi fed-batch fermentation conditions. We first assessed our ribosome profiling setup by inducing ribosome stalling at isoleucine codons using the antibiotic mupirocin, and found a pause preference for isoleucine codons preceded by E and P site codons with guanosine residues in their first nucleotide position. Interestingly, when we applied standard ribosomal profiling conditions we found again an enrichment of guanosine residues in the E and P site of ribosome pause sites, but this time also upstream of the ribosome pause site. This sequence motif deviates from previously described ribosome pausing motifs. For the highly expressed amylase gene amyM several strong ribosome pausing sites were detected, which remained present during the 64-hour long fermentation, and were neither related to rare codons nor to secondary protein structures. When surveying the genome, an interesting finding was the presence of strong ribosome pausing sites in several toxins genes. These potential ribosome stall sites may function in preventing inadvertent activity in the cytosol.
Project description:Ribosome pausing slows down translation and can affect protein synthesis. Improving translation efficiency can therefore be of commercial value. Here, we investigated the occurrence of ribosome pausing during amylase secretion by the industrial production organism Bacillus subtilis under semi fed-batch fermentation conditions. We first assessed our ribosome profiling setup by inducing ribosome stalling at isoleucine codons using the antibiotic mupirocin, and found a pause preference for isoleucine codons preceded by E and P site codons with guanosine residues in their first nucleotide position. Interestingly, when we applied standard ribosomal profiling conditions we found again an enrichment of guanosine residues in the E and P site of ribosome pause sites, but this time also upstream of the ribosome pause site. This sequence motif deviates from previously described ribosome pausing motifs. For the highly expressed amylase gene amyM several strong ribosome pausing sites were detected, which remained present during the 64-hour long fermentation, and were neither related to rare codons nor to secondary protein structures. When surveying the genome, an interesting finding was the presence of strong ribosome pausing sites in several toxins genes. These potential ribosome stall sites may function in preventing inadvertent activity in the cytosol.
Project description:Translation elongation factor P (EF-P) alleviates ribosome pausing at a subset of motifs encoding consecutive proline residues and is required for growth in many organisms. Here we show that Bacillus subtilis EF-P also alleviated ribosome pausing at sequences encoding tandem prolines, and ribosomes paused within several essential genes without a corresponding growth defect in an efp mutant. The B. subtilis efp mutant is instead impaired for flagellar biosynthesis which results in the abrogation of a form of motility called swarming. We isolate swarming suppressors of efp and identify mutations in 8 genes that suppressed the efp mutant swarming defect, many of which encode conserved ribosomal proteins or ribosome-associated factors. One mutation abolished a translational pause site within the flagellar C-ring component FliY to increase flagellar number and restore swarming motility in the absence of EF-P. Our data support a model wherein EF-P-alleviation of ribosome pausing may be particularly important for macromolecular assemblies like the flagellum that require precise protein stoichiometries.
Project description:Translation elongation factor P (EF-P) alleviates ribosome pausing at a subset of motifs encoding consecutive proline residues and is required for growth in many organisms. Here we show that Bacillus subtilis EF-P also alleviated ribosome pausing at sequences encoding tandem prolines, and ribosomes paused within several essential genes without a corresponding growth defect in an efp mutant. The B. subtilis efp mutant is instead impaired for flagellar biosynthesis which results in the abrogation of a form of motility called swarming. We isolate swarming suppressors of efp and identify mutations in 8 genes that suppressed the efp mutant swarming defect, many of which encode conserved ribosomal proteins or ribosome-associated factors. One mutation abolished a translational pause site within the flagellar C-ring component FliY to increase flagellar number and restore swarming motility in the absence of EF-P. Our data support a model wherein EF-P-alleviation of ribosome pausing may be particularly important for macromolecular assemblies like the flagellum that require precise protein stoichiometries.
Project description:We report the discovery of a simple environmental sensing mechanism for biofilm formation in the bacterium Bacillus subtilis that operates without the involvement of a dedicated RNA or protein. Certain serine codons, the four UCN codons, in the gene for the biofilm repressor SinR caused a lowering of SinR levels under biofilm-inducing conditions. Synonymous substitutions of these UCN codons with AGC or AGU impaired biofilm formation and gene expression. Conversely, switching AGC or AGU to UCN codons upregulated biofilm formation. Genome-wide ribosome profiling showed that ribosomes paused longer at UCN codons than at AGC or AGU during biofilm formation. Serine starvation recapitulated the effect of biofilm-inducing conditions on ribosome pausing and SinR production. As serine is one of the first amino acids to be exhausted at the end of exponential phase growth, ribosome pausing at serine codons may be exploited by other microbes in adapting to stationary phase. 4 samples for ribosome profiling and 2 samples for total mRNA profiling
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
Project description:Transcription by RNA polymerase (RNAP) is interrupted by pauses that play diverse regulatory roles. Although individual pauses have been studied in vitro, the determinants of pauses in vivo and their distribution throughout the bacterial genome remain unknown. Using nascent transcript sequencing we identify a 16 nt consensus pause sequence in E. coli that accounts for known regulatory pause sites as well as ~20,000 new in vivo pause sites. In vitro single-molecule and ensemble analyses demonstrate that these pauses result from RNAP/nucleic-acid interactions that inhibit next-nucleotide addition. The consensus sequence also leads to pausing by RNAPs from diverse lineages and is enriched at translation start sites in both E. coli and B. subtilis. Our results thus implicate a conserved mechanism unifying known and newly identified pause events. Examination of nascent transcripts in E. coli and B. subtilis. 6 samples of E. coli NET-seq, 1 sample of E. coli mRNA-seq, and 1 sample of B. subtilis NET-seq.
Project description:Ribosome profiling in archaea reveals leaderless translation, novel translational initiation sites, and ribosome pausing at single codon resolution