Entire reconstitution of tRNAs for active protein production in a cell-free system brings flexibility into the genetic code engineering. It can also contribute to the field of cell-free synthetic biology, which aims to construct self-replicable artificial cells. Herein, we developed a system equipped only with in vitro transcribed tRNA (iVTtRNA) based on a reconstituted cell-free protein synthesis (PURE) system. The developed system, consisting of 21 iVTtRNAs without nucleotide modifications, is able to synthesize active proteins according to the redesigned genetic code. Manipulation of iVTtRNA composition in the system enabled genetic code rewriting. Introduction of modified nucleotides into specific iVTtRNAs demonstrated to be effective for both protein yield and decoding fidelity, where the production yield of DHFR reached about 40% of the reaction with native tRNA at 30°C. The developed system will prove useful for studying decoding processes, and may be employed in genetic code and protein engineering applications.

Activating transcription factor 4 (ATF4), which is ubiquitously expressed, plays a crucial role in regulating various stress-responsive genes under pathophysiological conditions. Further, growth arrest and DNA damage-inducible gene 34 (GADD34), a downstream target of ATF4, has been reported to negatively regulate ATF4 expression. To understand the relationship between intrinsic ATF4 and GADD34 under resting and ER stress conditions, we used a novel gene editing approach, CRISPR/Cas9, to integrate antibiotic-resistant genes into the target genes, ATF4 and GADD34. First, we manipulated the ATF4 gene in the mouse neuroblastoma cell line, Neuro2a, and compared the ER stress responses between parental and ATF4-edited Neuro2a cells. Next, we established Neuro2a cells with edited GADD34 and ATF4/GADD34 genes and found that ATF4 acts as a proapoptotic factor, but GADD34 depletion did not attenuate the expression of cleaved caspase-3 induced by tunicamycin treatment. These findings provide new insights into the ATF4 signaling cascades. Additionally, the rapid establishment of cells lacking multiple genes using this CRISPR/Cas9 system will be a powerful tool for exploring various cellular issues under pathophysiological conditions.

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杉浦直樹 1, 2) ・辻 孝子 1) ・藤井 潔 1) ・加藤恭宏 1) ・坂 紀邦 1, 3) ・遠山孝通 1, 4) ・早野由里子 5) ・井澤敏彦 1) (1) 愛知県農業総合試験場，愛知郡長久手町，〒 480-1193， 2) 現愛知県立農業大学校，岡崎市，〒 444-0802， 3) 現愛知県農業総合試験場山間農業 研究所，東加茂郡稲武町，〒 444-2513， 4) 現愛知県知多農林水産事務所，半田市，〒 475-0903， 5) 北海道農業研究センター，札幌市，〒 062-8555