A Synthetic DNA Base Pair Enables the Discovery of Novel Protein Therapeutics

Over the past two decades, synthetic biologists have developed elegant methods to add diversity or re-appropriate redundancy in the genetic code for the introduction of a vast array of unnatural amino acids with unique properties.  These efforts promise to revolutionize applied science with new molecular tools and strategies for protein-based therapeutics.  However, unknown biological constraints have thus far largely precluded the encoding of more than one unnatural amino acid at a time.  As an alternative strategy to expand the genetic code without interfering with the naturally-evolved coding structure, the Romesberg lab at the Scripps Research Institute has developed an unnatural DNA base pair that enables addition of multiple orthogonal codons to the natural set.  This base pair is fully-compatible with replication and transcription in vitro, and was demonstrated to be faithfully replicated in E. coli cells.

Synthorx Inc. is a drug discovery company that was recently established to commercialize this technology and develop novel protein-based therapeutics in vitro and within semi-synthetic cells.  In collaboration with the Romesberg lab, we have developed an in vitro protein expression system that is compatible with the expanded genetic code.  Using this system, we have discovered a large variety of unnatural codons that are fully orthogonal and support high-level transcription and translation of unnatural genetic information into unnatural proteins.  Importantly, these codons function as orthogonal genetic elements that do not require modification or manipulation of the organism’s natural coding structure.  We will discuss the features and performance of our system for in vitro protein production as well as our efforts to expand this technology into E. coli.   Our ability to genetically-encode protein therapeutics of any size that contain multiple, distinct unnatural amino acids allows for the development of novel therapeutic proteins that have not been accessible using existing technologies.