PROTAC-CID Gene Switches for Multiplex and Orthogonal Regulation
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Solution Overview
Problem
Existing chemically induced dimerization (CID) systems for gene regulation suffer from limited multiplexing capability, low efficiency, and uncertainty for in vivo applications, particularly due to issues with immunosuppressive effects and high concentration requirements of small molecules like rapamycin and gibberellic acid, limiting their clinical application potential.
Innovation Solution
Repurpose proteolysis targeting chimeras (PROTACs) to create a scalable CID system by combining fusion proteins with small-molecule binding domains and DNA binding domains, enabling orthogonal and multiplex gene regulation through the ubiquitin-proteasome system, using adeno-associated viral vectors for delivery and allowing for precise spatiotemporal control of gene expression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If naturally existing small molecules from bacteria or plants are used in CID systems, then the systems can be established, but the number of highly efficient CIDs remains limited and immunosuppressive effects occur
Solution Approach 1:
The patent changes the chemical structure parameters of small molecules by designing and synthesizing novel CID inducers with specific molecular structures (e.g., compound 1, compound 2, compound 3) that bind to FKBP12 and elicit dimerization without immunosuppressive effects, thereby expanding the toolbox while eliminating harmful side effects
Solution Approach 2:
The patent employs synthetic small molecule inducers that can be rapidly designed and synthesized as needed, replacing the need for naturally occurring compounds with customizable, disposable-like molecules that provide precise control without long-term immunosuppressive consequences
2Reliability
If existing CID inducers such as rapamycin are used, then protein dimerization can be achieved, but high concentrations are required for efficient dimerization
Solution Approach 1:
The patent optimizes the binding affinity parameters of the small molecule inducers to FKBP12, achieving high-efficiency dimerization at nanomolar concentrations (e.g., IC50 values in the nanomolar range) by modifying the molecular structure to enhance interaction strength, thereby reducing the quantity of substance needed
3Adaptability or versatility
If bacterial origin CID systems are used, then gene regulation can be achieved, but immune responses and antibiotic usage concerns arise
Solution Approach 1:
The patent extracts the essential dimerization function from bacterial-origin systems and implements it through synthetic small molecules that do not rely on bacterial proteins, thereby maintaining gene regulation capability while removing the source of immune responses and antibiotic resistance concerns
Solution Approach 2:
The patent introduces synthetic small molecule intermediaries (compound 1, compound 2, compound 3) that mediate the interaction between FKBP12 and the target protein, replacing direct bacterial protein interactions with these chemical mediators to eliminate immune responses
4Adaptability or versatility
If PROTACs are repurposed for CID applications, then a scalable system with multiplex capability is achieved, but the system complexity increases
Solution Approach 1:
The patent segments the PROTAC molecule into distinct functional components (warhead, linker, anchor ligand) and applies this modular architecture to create multiple orthogonal CID systems (e.g., PROTAC-CID1, PROTAC-CID2, PROTAC-CID3) that can be independently controlled, thereby achieving multiplex capability through systematic segmentation
Solution Approach 2:
The patent creates a universal PROTAC-CID platform where the same basic PROTAC structure can be configured for different gene regulation functions by changing the protein partners (e.g., FKBP12-FRB, FKBP12-VP16, GAL4-VPR), allowing one system architecture to serve multiple regulatory purposes
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The PROTAC-CID system achieves high-efficiency, orthogonal, and digitally inducible gene regulation, suitable for complex gene therapy applications, with reduced immune response risk and expanded clinical applicability, including inducible expression of DNA recombinases, base editors, and prime editors.
Implementation Method 1
PROTACs are composed of a warhead that binds to the target protein, an anchor ligand that binds to an E3 ubiquitin ligase, and a linker that ties these two parts together. At least 1600 PROTACs have been developed, acting on more than 100 human protein targets with multiple E3 ubiquitin ligases
Implementation Method 2
The chemically induced dimerization (CID) system-based inducible gene activation tool is composed of two fusion proteins with small-molecule binding domains fused to a DNA binding domain and a transcriptional activation domain, respectively. In the presence of a small molecule, both fusion proteins bind to the same small molecule, recruit the transactivation domain to DNA, and activate gene expression
Data Source
AI summary
The present disclosure provides proteolysis targeting chimeras-based scalable CID (PROTAC-CID) system that repurpose PROTACs for inducible, orthogonal, and multiplex transcriptional activation. When coupled with multi-layer genetic circuits, PROTAC-CID enables digitally inducible DNA manipulations with low basal levels. These PROTAC-CID systems can be delivered in vivo by adeno-associated virus (AAV) to allow ON-OFF genetic switches.