Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany.
Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany.
Mol Cell. 2017 May 18;66(4):558-567.e4. doi: 10.1016/j.molcel.2017.04.023.
Ribosome frameshifting during translation of bacterial dnaX can proceed via different routes, generating a variety of distinct polypeptides. Using kinetic experiments, we show that -1 frameshifting predominantly occurs during translocation of two tRNAs bound to the slippery sequence codons. This pathway depends on a stem-loop mRNA structure downstream of the slippery sequence and operates when aminoacyl-tRNAs are abundant. However, when aminoacyl-tRNAs are in short supply, the ribosome switches to an alternative frameshifting pathway that is independent of a stem-loop. Ribosome stalling at a vacant 0-frame A-site codon results in slippage of the P-site peptidyl-tRNA, allowing for -1-frame decoding. When the -1-frame aminoacyl-tRNA is lacking, the ribosomes switch into -2 frame. Quantitative mass spectrometry shows that the -2-frame product is synthesized in vivo. We suggest that switching between frameshifting routes may enrich gene expression at conditions of aminoacyl-tRNA limitation.
核糖体在翻译细菌 dnaX 时的框架移位可以通过不同的途径进行，产生各种不同的多肽。通过动力学实验，我们表明 -1 框架移位主要发生在与滑溜序列密码子结合的两个 tRNA 转移期间。该途径依赖于滑溜序列下游的 mRNA 结构茎环，并且在氨酰基-tRNA 丰富时起作用。然而，当氨酰基-tRNA 供应不足时，核糖体切换到不依赖茎环的替代框架移位途径。核糖体在空位 0 框架 A 位密码子处停顿导致 P 位肽酰基-tRNA 滑动，从而允许 -1 框架解码。当缺少 -1 框架氨酰基-tRNA 时，核糖体切换到 -2 框架。定量质谱分析表明，-2 框架产物在体内合成。我们认为，在氨酰基-tRNA 限制的条件下，框架移位途径的切换可能会丰富基因表达。
