The nascent field of synthetic biology offers the promise of engineered gene
networks with novel biological phenotypes. Numerous synthetic gene circuits
have been created in the past decade, including bistable switches,
oscillators, and logic gates. Despite a booming field and although recently
developed designs of regulatable gene networks are ingenious, there are
limitations in routinely engineering synthetic biological systems. Indeed,
there is a need for rationalizing the design of novel regulatable gene