Translation efficiency is maintained at elevated temperature in Escherichia coli

Cellular protein levels are dictated by the balance between gene transcription, mRNA translation, and protein degradation, among other factors. Translation requires the interplay of several RNA hybridization processes, which are expected to be temperature-sensitive. We used ribosome profiling to monitor translation in Escherichia coli at 30 degrees C and to investigate how this changes after 10-20 min of heat shock at 42 degrees C. Translation efficiencies are robustly maintained after thermal heat shock and after mimicking the heat-shock response transcriptional program at 30 degrees C by overexpressing the heat shock sigma factor encoded by the rpoH gene. We compared translation efficiency, the ratio of ribosome footprint reads to mRNA reads for each gene, to parameters derived from gene sequences. Genes with stable mRNA structures, non-optimal codon use, and those whose gene product is cotranslationally translocated into the inner membrane are generally less highly translated than other genes. Comparison with other published datasets suggests a role for translational elongation in coupling mRNA structures to translation initiation. Genome-wide calculations of the temperature dependence of mRNA structure predict that relatively few mRNAs show a melting transition between 30 and 42 degrees C, consistent with the observed lack of changes in translation efficiency. We developed a linear model with six parameters that can predict 38% of the variation in translation efficiency between genes, which may be useful in interpreting transcriptome data.