Synthetic Feedback Circuit for Protein Expression Control

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Solution Overview

Problem

Current methods for regulating protein activity within cells, particularly for gene expression, face challenges in controlling endogenous gene activity and implementing fully synthetic transcriptional regulation.

Innovation Solution

A synthetic feedback circuit comprising a first polypeptide activated by an external stimulus, a target protein, and a fusion protein with a domain that binds to the first polypeptide and a degron or E3 ligase-recruiting domain, where the first polypeptide activates the expression of the target protein and the fusion protein, leading to the degradation of the first polypeptide, thereby regulating the target protein's expression through feedback.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If gene expression regulation methods are used to control protein activity, then gene expression can be regulated, but controlling endogenous gene activity remains challenging

Engineering Contradiction:

Improvegene expression regulation capabilityVSAvoidcontrol of endogenous gene activity

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The patent introduces a synthetic transcription factor as an intermediary molecule that mediates between external control signals and endogenous gene expression. This synthetic TF can be externally controlled (e.g., through small molecules or light) while directly regulating endogenous genes, thus bridging the gap between external control capability and endogenous gene regulation difficulty

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent segments the gene regulation process into controllable modules: a synthetic transcription factor domain that can be externally controlled, and a target gene activation domain. This segmentation allows independent optimization of control mechanisms and target gene regulation, making endogenous gene control more manageable

Inventive Principle:

Principle #1Segmentation

2Manufacturing precision

If feedback control circuits are implemented to regulate protein expression, then protein expression levels can be precisely controlled, but the circuit complexity increases

Engineering Contradiction:

Improveprotein expression level control precisionVSAvoidfeedback circuit structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent implements a feedback control circuit where the synthetic transcription factor activates both the target gene and a reporter gene, and the reporter signal feeds back to modulate the transcription factor activity. This creates a closed-loop system that automatically adjusts protein expression levels to maintain precision while using modular components to manage complexity

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The synthetic transcription factor is designed as a universal regulator that can control multiple downstream genes simultaneously (both target genes and reporter genes). This multi-functionality reduces the need for separate control circuits for each gene, thereby simplifying the overall circuit structure while maintaining precise control over protein expression levels

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

This approach allows for precise control of protein expression levels, reducing peak protein levels and total protein production by up to 90% compared to circuits without feedback control, demonstrating effective regulation of protein activity within cells.

Implementation Method 1

a fusion protein comprising: (i) a domain that binds to the target protein of (b) and (ii) a degron or E3 ligase-recruiting domain. In these embodiments, the first polypeptide of (a), in its activated form, independently activates the expression of (b) and (c) and the fusion protein of (c) binds to the first polypeptide of (a), thereby causing degradation of the first polypeptide in trans.

Methodology Applied

Scientific EffectUbiquitination:

Implementation Method 2

the fusion protein of (c) binds to the first polypeptide of (a), thereby causing degradation of the first polypeptide in trans

Methodology Applied

Scientific EffectProteasome degradation:

Data Source

PatentUS20250092419A1Synthetic targeters of ubiquitination and degradation (STUDS) as effectors for feedback control in mammalian cells

Publication Date: 2025.03.20 RGT UNIV OF CALIFORNIA

AI summary

Described herein is a cell comprising a feedback circuit. In some embodiment, the circuit may comprise: (a) a first polypeptide that is activated by an external stimulus and, downstream from the first polypeptide: (b) a target protein and (c) a fusion protein comprising: (i) a domain that binds to the target protein of (b) and (ii) a degron or E3 ligase-recruiting domain. In these embodiments, the first polypeptide of (a), in its activated form, independently activates the expression of (b) and (c); and the fusion protein of (c) binds to the first polypeptide of (a), thereby causing degradation of the first polypeptide in trans. Methods using the cell are also provided.