title: Expanding the genetic code of Caenorhabditis elegans using bacterial aminoacyl-tRNA synthetase/tRNA pairs.
abstract: The genetic code specifies 20 common amino acids and is largely preserved in both single and multicellular organisms. Unnatural amino acids (Uaas) have been genetically incorporated into proteins by using engineered orthogonal tRNA/aminoacyl-tRNA synthetase (RS) pairs, enabling new research capabilities and precision inaccessible with common amino acids. We show here that Escherichia coli tyrosyl and leucyl amber suppressor tRNA/RS pairs can be evolved to incorporate different Uaas in response to the amber stop codon UAG into various proteins in Caenorhabditis elegans. To accurately report Uaa incorporation in worms, we found that it is crucial to integrate the UAG-containing reporter gene into the genome rather than to express it on an extrachromosomal array from which variable expression can lead to reporter activation independent of the amber-suppressing tRNA/RS. Synthesizing a Uaa in a dipeptide drives Uaa uptake and bioavailability. Uaa incorporation has dosage, temporal, tRNA copy, and temperature dependencies similar to those of endogenous amber suppression. Uaa incorporation efficiency was improved by impairing the nonsense-mediated mRNA decay pathway through knockdown of smg-1. We have generated stable transgenic worms capable of genetically encoding Uaas, enabling Uaa exploitation to address complex biological problems within a metazoan. We anticipate our strategies will be generally extendable to other multicellular organisms.
authors.affiliation: Jack H. Skirball Center for Chemical Biology and Proteomics, Glenn Center for Aging Research, The Salk Institute for Biological Studies, Jolla, California 92037, United States.
authors.forename: Angela R
authors.initials: AR
authors.lastname: Parrish
authors.forename: Xingyu
authors.initials: X
authors.lastname: She
authors.forename: Zheng
authors.initials: Z
authors.lastname: Xiang
authors.forename: Irene
authors.initials: I
authors.lastname: Coin
authors.forename: Zhouxin
authors.initials: Z
authors.lastname: Shen
authors.forename: Steven P
authors.initials: SP
authors.lastname: Briggs
authors.forename: Andrew
authors.initials: A
authors.lastname: Dillin
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
mesh_terms: D000604:Amino Acyl-tRNA Synthetases / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000201:enzymology / Q000235:genetics*; D005815:Genetic Code / Q000235:genetics*; D012343:RNA, Transfer / Q000235:genetics* / Q000378:metabolism
chemical_list: D012343:RNA, Transfer; D000604:Amino Acyl-tRNA Synthetases