Zhang Yorke, Ptacin Jerod L, Fischer Emil C, Aerni Hans R, Caffaro Carolina E, San Jose Kristine, Feldman Aaron W, Turner Court R, Romesberg Floyd E
Department of Chemistry, The Scripps Research Institute, La Jolla, California 92037, USA.
Synthorx, Inc., La Jolla, California 92037, USA.
Nature. 2017 Nov 29;551(7682):644-647. doi: 10.1038/nature24659.
Since at least the last common ancestor of all life on Earth, genetic information has been stored in a four-letter alphabet that is propagated and retrieved by the formation of two base pairs. The central goal of synthetic biology is to create new life forms and functions, and the most general route to this goal is the creation of semi-synthetic organisms whose DNA harbours two additional letters that form a third, unnatural base pair. Previous efforts to generate such semi-synthetic organisms culminated in the creation of a strain of Escherichia coli that, by virtue of a nucleoside triphosphate transporter from Phaeodactylum tricornutum, imports the requisite unnatural triphosphates from its medium and then uses them to replicate a plasmid containing the unnatural base pair dNaM-dTPT3. Although the semi-synthetic organism stores increased information when compared to natural organisms, retrieval of the information requires in vivo transcription of the unnatural base pair into mRNA and tRNA, aminoacylation of the tRNA with a non-canonical amino acid, and efficient participation of the unnatural base pair in decoding at the ribosome. Here we report the in vivo transcription of DNA containing dNaM and dTPT3 into mRNAs with two different unnatural codons and tRNAs with cognate unnatural anticodons, and their efficient decoding at the ribosome to direct the site-specific incorporation of natural or non-canonical amino acids into superfolder green fluorescent protein. The results demonstrate that interactions other than hydrogen bonding can contribute to every step of information storage and retrieval. The resulting semi-synthetic organism both encodes and retrieves increased information and should serve as a platform for the creation of new life forms and functions.
至少从地球上所有生命的最后一个共同祖先开始，遗传信息就被存储在一个由四个字母组成的字母表中，通过形成两个碱基对来进行传播和检索。合成生物学的核心目标是创造新的生命形式和功能，而实现这一目标最普遍的途径是创造半合成生物体，其DNA含有另外两个字母，形成第三个非天然碱基对。此前生成此类半合成生物体的努力最终造就了一种大肠杆菌菌株，该菌株借助三角褐指藻的核苷三磷酸转运蛋白，从培养基中导入所需的非天然三磷酸，然后利用它们来复制含有非天然碱基对dNaM-dTPT3的质粒。尽管与天然生物体相比，这种半合成生物体存储了更多信息，但信息的检索需要将非天然碱基对在体内转录为mRNA和tRNA，用非标准氨基酸对tRNA进行氨酰化，以及非天然碱基对在核糖体解码过程中的有效参与。在此，我们报告了将含有dNaM和dTPT3的DNA在体内转录为带有两种不同非天然密码子的mRNA以及带有同源非天然反密码子的tRNA，并且它们在核糖体上有效解码，以指导将天然或非标准氨基酸位点特异性地掺入超级折叠绿色荧光蛋白中。结果表明，除氢键以外的相互作用可以对信息存储和检索的每一步都有所贡献。由此产生的半合成生物体既能编码又能检索更多信息，应可作为创造新生命形式和功能的平台。
