Sense codon reassignment enables viral resistance and encoded polymer synthesis

Designing bacterial superpowers Biological systems read all 64 triplet codons in DNA to encode the synthesis of proteins composed of 20 canonical amino acids. Robertson et al. created cells that do not read several codons and showed that this confers complete resistance to viruses, which normally rely on the host cell's ability to read all the codons in the viral genome to reproduce (see the Perspective by Jewel and Chatterjee). The authors reassigned each codon to several noncanonical amino acids (ncAAs). This advance enables the efficient synthesis of proteins containing three distinct ncAAs and the encoded synthesis of entirely noncanonical polymers and macrocycles. Science , abg3029, this issue p. 1057 ; see also abi9892, p. 1040