Highly modular bow-tie gene circuits with programmable dynamic behavior

Supplementary Figure 1. Schematic representation and dose-response curves of different recombinase switches. a | Mechanistic illustration of the underlying recombination processes indicating the region of interest (ROI) being modified by a recombinase and the site-specific recombination sites (blue triangles). b | Detailed description of the recombinase switches. In order to express a target gene, the switch construct (left) has to undergo site-specific recombination. Triangles indicate recombinase recognition sites. The PhiC31-Inversion Switch is based on non-identical sites attP and attB and is thus intrinsically irreversible because post-recombination sites are different from the original ones. The Cre Excision Switch is irreversible because the excision of GFP by flanking loxP sites places DsRed in frame and back integration is extremely inefficient. The Flex Switch is irreversible because it contains two pairs of distinct sites. This is a two-step process involving inversion and excision, leaving a pair of heterospecific sites (loxP and lox2272 for Cre and FRT and F3 for FlpO) that cannot both serve as a substrate for intramolecular reaction. Only after successful recombination, the construct (right) is able to express the target gene. The resulting constructs on the right were pre-made to serve as a positive control. c | Dose-response of the individual switches. In order to test recombination performance of the different recombinases, PhiC31, Cre and FlpO driven by a constitutive promoter Ef1a were cotransfected with either the switch construct (orange dots) or the pre-recombined construct