Fig. 4: Permissive interception synthetic memory via anti-repression.

a A schematic summarizing the mechanism and genetic construct (deletion circuit) used to assess A118 recombinase interception for different anti-repressors directed at different operators placed in the P + 1 position (described in Fig. 2j). Anti-repressors have the opposite induction/DNA-binding relationship to repressors; anti-repressors bind DNA when induced and do not bind DNA when not induced. The A118 recombinase and relevant anti-repressor are constitutively expressed in all cases. As in Fig. 3, the anti-repressor used are comprised of two modular domains: (1) a regulatory core domain that allows the anti-repressor to be induced by a different ligand, and (2) a DNA-binding domain that allows the anti-repressor to bind to a different operator. In STATE 1, induced anti-repressor binding at the operator blocks recombinase function, protecting the circuit from deletion. In the absence of ligand, the anti-repressor cannot bind to the operator, bringing the circuit to STATE 2, where the recombinase can access the attP site to recombine the circuit (bringing the circuit to STATE 3). b Assay data for deprotected (minus ligand) circuits vs. intercepted (induced) circuits using I^A(5) across six different DNA-binding domain/operator pairs. Assay data using the same set of DNA-binding domain/operator pairs as (b) paired with different regulatory core domains as follows: c R^A(1), d F^A(1), e S^A(1), and f P^A. (inset) Symbols for the circuit parts and modular anti-repressor components used, including six DNA-binding domains conferring alternate DNA recognition, the six DNA operators where those DNA-binding domains can bind (color-matched), and five regulatory core domains sensitive to different ligands. Source data are provided as a Source Data file. Data in (b–f) represent the average of n = 6 biological replicates. Error bars correspond to the SEM of these measurements.