Expanding the genetic code of Mus musculus
A recent work published in Nature communications describes in vivo control of protein acetylation in transgenic mouse by expanding the genetic code of mouse. Stable integration of orthogonal enzyme machinery into the mouse genome enables site-specific incorporation of unnatural amino acids into a target protein in response to the amber stop codon. Researchers at KAIST in the Department of Chemistry, demonstrated temporal and spatial control of protein acetylation in various organs of the transgenic mouse. This strategy will provide a powerful tool for systematic in vivo study of cellular proteins in the most commonly used mammalian model organism for human physiology and disease.
Post-translational modifications (PTMs) are crucial for regulating protein function, and thus play a key role in many essential cellular processes. Among the diverse PTMs, lysine acetylation is a reversible modification that dynamically regulates functions of a wide range of eukaryotic proteins. Therefore, aberrant acetylation of many cellular proteins is associated with various human diseases, including cancer. The amber codon suppression technique, based on the use of an orthogonal aminoacyl-tRNA synthetase/tRNA pair, has been successfully developed as a means to expand the function of a protein in the laboratory. However, despite extensive efforts, this powerful approach has not been extended to the multi-organ animal Mus musculus (mouse). The KAIST researchers have thus developed a novel strategy for in vivo control of acetylation in mouse – the most prevalent model of human physiology and disease – by applying an amber codon suppression techniqueto transgenic mouse.
The researchers report, for the first time, the generation of a mouse strain with an expanded genetic code, allowing site-specific incorporation of unnatural amino acids (UAAs) including N-acetyl-lysine (AcK) in response to the amber codon in various organs. At first, the AcK-incorporation system composed of an orthogonal N-acetyl-lysyl-tRNA synthetase (AcKRS)/tRNA pair and a model protein gene, a green fluorescent protein (GFP) harboring amber codon at targeted position, was constructed in mammalian cell for system optimization. Then, the transgenic mouse carrying the AcK-incorporation system was generated by chromosomal integration of AcKRS and GFP transgenes into mouse genome. The resultant AcKRS/GFP transgenic mouse exhibited temporal and spatial expression of acetylated model protein upon acetyl-lysine (AcK) injection. In other words, this approach facilitates rapid onset of acetylation of a specific lysine residue of a target protein at any developmental stage or selected tissue of the mouse. Such temporal and spatial control of protein acetylation will be of prime importance for investigating many essential biological processes and human diseases at the tissue and organism level. The authors anticipate that transgenic mice with an expanded genetic code will offer a robust, versatile and powerful tool for more precisely and systematically investigating various aspects of cellular proteins.
Songmi Han#, Aerin Yang#, Soonjang Lee, Han-Woong Lee, Chan Bae Park* & Hee-Sung Park*, Nature Communications, 2017, 21 February, 8, 14568.
* Lab information