A Genetically Encodable and Chemically Disruptable System for Synthetic Post-Translational Modification Dependent SynNotch Signaling

We describe an engineered "writer/reader" framework for programming post-translational control into synthetic mammalian signaling proteins. In this approach, a bacterially-derived biotin protein ligase (BirA) was used as a "writer" element for the modification of artificial receptors and transcription factors containing a biotin acceptor peptide (AP) fusion tag. To enable modification events to transmit biochemical information, we designed encodable "reader" modules using sequences from a biotinamide-binding antibody. Proteins fused to reader domains were able to interact with AP-tagged polypeptides in a biotinylation-dependent manner, and control over the timing and extent of these interactions could be modulated through both genetic and chemically-based strategies. Genetic and cell-specific control over AP-reader module interactions was achieved via regulated BirA expression, and the interaction states of both intra-and inter-cellular complexes could be modulated with biotinamide-based and bioorthogonally-functionalized compounds. The utility of this approach was demonstrated by installing post-translational and chemogenetic control into synthetic Notch ("SynNotch")-based systems.