Wyss Institute for Biologically Inspired Engineering, 3 Blackfan Circle, Boston, MA 02115, USA.
Science. 2013 Oct 25;342(6157):475-9. doi: 10.1126/science.1241934. Epub 2013 Sep 26.
Most amino acids are encoded by multiple codons, and codon choice has strong effects on protein expression. Rare codons are enriched at the N terminus of genes in most organisms, although the causes and effects of this bias are unclear. Here, we measure expression from >14,000 synthetic reporters in Escherichia coli and show that using N-terminal rare codons instead of common ones increases expression by ~14-fold (median 4-fold). We quantify how individual N-terminal codons affect expression and show that these effects shape the sequence of natural genes. Finally, we demonstrate that reduced RNA structure and not codon rarity itself is responsible for expression increases. Our observations resolve controversies over the roles of N-terminal codon bias and suggest a straightforward method for optimizing heterologous gene expression in bacteria.
大多数氨基酸都由多个密码子编码，而密码子的选择对蛋白质表达有很强的影响。在大多数生物体中，稀有密码子在基因的 N 端富集，尽管这种偏好的原因和影响尚不清楚。在这里，我们在大肠杆菌中测量了超过 14000 个合成报告基因的表达情况，结果表明，使用 N 端稀有密码子而不是常见密码子可以使表达水平提高约 14 倍（中位数为 4 倍）。我们定量分析了单个 N 端密码子对表达的影响，并表明这些影响塑造了天然基因的序列。最后，我们证明是 RNA 结构的减少而不是密码子的稀有性本身导致了表达的增加。我们的观察结果解决了 N 端密码子偏好的作用的争议，并为在细菌中优化异源基因表达提供了一种简单的方法。
