Tradeoffs in the design of RNA thermometers.

The synthesis of RNA thermometers is aimed at achieving temperature responses with desired thresholds and sensitivities. Although previous works have generated thermometers with a variety of thresholds and sensitivities as well as guidelines for design, possible constraints in the achievable thresholds and sensitivities remain unclear. We addressed this issue using a two-state model and its variants, as well as melt profiles generated from thermodynamic computations. In the two-state model, we found that the threshold was inversely proportional to the sensitivity, in the case of a fixed energy difference between the two states. Notably, this constraint could persist in variations of the two-state model with sequentially unfolding states and branched parallel pathways. Furthermore, the melt profiles generated from a library of thermometers exhibited a similar constraint. These results should inform the design of RNA thermometers as well as other responses that are mediated in a similar fashion.

Design of a Toolbox of RNA Thermometers.

RNA thermometers are RNA regulatory elements that convert temperature into a functional biological response through a temperature-induced conformational change. These regulatory elements have been investigated in numerous natural contexts and have been designed for synthetic biology as well. A basic challenge has been the design of an RNA thermometer whose final activity in response to temperature matches a prespecified response, in terms of its sensitivity, threshold, and leakiness. This chapter provides a methodology for the design of a toolbox of RNA thermometers. We describe considerations for the conceptual design, a computational assessment, and strategies for experimental synthesis and measurement.