From the Departments of Chemistry and Molecular Medicine and.
California Institute of Quantitative Biosciences and Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, California 94158.
J Biol Chem. 2018 Jan 19;293(3):777-793. doi: 10.1074/jbc.RA117.000284. Epub 2017 Nov 28.
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 at 30 °C and to investigate how this changes after 10-20 min of heat shock at 42 °C. Translation efficiencies are robustly maintained after thermal heat shock and after mimicking the heat-shock response transcriptional program at 30 °C by overexpressing the heat shock σ factor encoded by the 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 °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.
细胞内蛋白质的水平取决于基因转录、mRNA 翻译和蛋白质降解等因素之间的平衡。翻译需要几种 RNA 杂交过程的相互作用,这些过程预计对温度敏感。我们使用核糖体分析来监测 30°C 下的翻译,并研究在 42°C 热休克 10-20 分钟后这种翻译如何变化。在热休克后和通过过表达由 基因编码的热休克 σ 因子在 30°C 下模拟热休克反应转录程序后,翻译效率都得到了稳健的维持。我们将翻译效率(每个基因的核糖体足迹读数与 mRNA 读数的比值)与从基因序列得出的参数进行了比较。具有稳定 mRNA 结构、非最佳密码子使用以及其产物在共翻译过程中被转运到内膜的基因,通常比其他基因的翻译效率低。与其他已发表数据集的比较表明,翻译延伸在将 mRNA 结构与翻译起始偶联方面起着作用。基于全基因组的 mRNA 结构对温度依赖性的计算预测,在 30 和 42°C 之间,相对较少的 mRNA 会出现熔解转换,这与观察到的翻译效率没有变化一致。我们开发了一个具有六个参数的线性模型,可以预测基因之间翻译效率的 38%的变化,这对于解释转录组数据可能是有用的。