Non-optimal codon usage affects expression, structure and function of clock protein FRQ.
Non-optimal codon usage affects expression, structure and function of clock protein FRQ.
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密码子使用偏差几乎在所有基因组中都存在，这被认为是高表达基因高效准确翻译的选择结果。密码子的使用也与转录、剪接和RNA结构的控制有关。许多基因表现出很少的密码子使用偏差，这被认为反映了mRNA翻译缺乏选择。然而，另外，非最佳密码子使用可能具有生物学意义。神经孢子菌频率蛋白（FRQ）的节律性表达和正常功能对生物钟功能至关重要。在这里，我们发现，与神经孢子虫中的大多数基因不同，frq在其整个开放阅读框中表现出非最佳密码子使用。优化frq密码子的使用消除了显性和分子昼夜节律。密码子优化不仅增加了FRQ水平，而且令人惊讶的是，还导致FRQ蛋白的构象改变，改变了FRQ磷酸化谱和稳定性，损害了昼夜反馈回路的功能。这些结果表明，非最优密码子的使用对frq的生物钟功能至关重要。我们的研究提供了一个非最佳密码子使用如何调节蛋白质表达并实现最佳蛋白质结构和功能的例子。
Codon usage bias has been observed in almost all genomes and is thought to result from selection for efficient and accurate translation of highly expressed genes. Codon usage is also implicated in the control of transcription, splicing and RNA structure. Many genes exhibit little codon usage bias, which is thought to reflect a lack of selection for mRNA translation. Alternatively, however, non-optimal codon usage may have biological significance. The rhythmic expression and the proper function of the Neurospora FREQUENCY (FRQ) protein are essential for circadian clock function. Here we show that, unlike most genes in Neurospora, frq exhibits non-optimal codon usage across its entire open reading frame. Optimization of frq codon usage abolishes both overt and molecular circadian rhythms. Codon optimization not only increases FRQ level but surprisingly, also results in conformational changes in FRQ protein, altered FRQ phosphorylation profile and stability, and impaired functions in the circadian feedback loops. These results indicate that non-optimal codon usage of frq is essential for its circadian clock function. Our study provides an example of how non-optimal codon usage functions to regulate protein expression and to achieve optimal protein structure and function.