Synthetic Biological Circuits within an Orthogonal Central Dogma

Synthetic biology strives to reliably control cellular behavior, typically in the form of user-designed interactions of biological components to produce a predetermined output. Engineered circuit components are frequently derived from natural sources and are therefore often hampered by inadvertent interactions with host machinery, most notably within the host central dogma. Reliable and predictable gene circuits require the targeted reduction or elimination of these undesirable interactions to mitigate negative consequences on host fitness and develop context-independent bioactivities. Here, we review recent advances in biological orthogonalization, namely the insulation of researcher-dictated bioactivities from host processes, with a focus on systematic developments that may culminate in the creation of an orthogonal central dogma and novel cellular functions. Development of fully synthetic nucleobase pairs that faithfully interact in living cells, and their applications in creating semisynthetic organisms with expanded and orthogonal information-carrying capacity.Harnessing naturally occurring and mutually orthogonal DNA replication systems to enable replication of target genes. Highly error-prone variations on these systems enable robust directed evolution of biomolecules.Engineering and directed evolution of mutually orthogonal transcription factors that operate with high dynamic range, low background, and respond to a wide repertoire of stimuli in vivo.Recent developments in in vivo orthogonal protein translation including: orthogonal RBS–orthogonal anti-RBS pairs, covalently linked rRNA subunits to discover novel enzymatic capabilities, improved incorporation of non-canonical amino acids and decoding quadruplet codons.