SYNTHETIC CIRCUIT: In this example of a typical transducer, the genetic construct (top) includes an amplifier response element and a carefully positioned transcription factor response element upstream of a promoter that drives expression of a fusion gene (the combined effector of choice and an amplifier). In the presence of a specific endogenous transcription factor, which binds to the transcription factor response element, the fusion gene is expressed. Cleavage of the fusion protein releases the amplifier, which together with the transcription factor drives much stronger expression. The system is like a positive feedback loop, but neither the transcription factor nor the amplifier alone can drive strong expression—they need each other.
© LUCY READING-IKKANDA
Some synthetic biology applications use cells as mere hosts for engineered genetic circuits—for example, when cells act as factories for desired molecules. For other applications, however, researchers would like to integrate the synthetic circuits with the cell’s own pathways.
Such integrated systems could be used to sense particular molecules and induce appropriate responses. For instance, detection of a metastasis-inducing protein in a cancer cell might be used to trigger that cell’s suicide. “The concept is that these synthetic circuits will be able to read out bits and pieces of information from the cell and interpret them to make decisions and drive the cell in different directions,” says Yaakov “Kobi” Benenson of the Federal Institute of Technology, or ETH, in Zurich.
Benenson and colleagues have recently ...
