Engineering Protein-Based Parts for Genetic Devices in Mammalian Cells

Synthetic biology has been advancing cellular and molecular biology studies through the design of synthetic circuits capable to examine diverse endogenously or exogenously driven regulatory pathways. While early genetic devices were engineered to be insulated from intracellular crosstalk, more recently the need of achieving dynamic control of cellular behavior has led to the development of smart interfaces that connect signal information (sensor) to desired output activation (actuator). Sensor-actuator circuits can respond to diverse inputs, including small molecules, exogenous and endogenous mRNA, noncoding RNA (i.e., miRNA), and proteins to regulate downstream events, transcriptionally, posttranscriptionally, and translationally. These devices require attentive engineering to either create complex chimeric proteins or modify protein structures to be amenable to the specific circuits' architecture and/or purpose. In this chapter, we describe how to implement two different protein-based devices in mammalian cells: (1) a modular platform that sense and respond to disease-associated proteins and (2) a protein-based system that allows simultaneous regulation of RNA translation and protein activity, via RNA-protein and newly engineered protein-protein interactions.