Dual Control Protein Expression via Antibiotic-Responsive Degradation
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Solution Overview
Problem
Current systems for controlling gene expression and protein degradation in living cells are inefficient, leading to cytotoxicity and difficulty in accurately determining gene expression effects, and require additional proteins and antibiotics like rapamycin, which have unknown effects and handling challenges.
Innovation Solution
A dual control system using an expression vector with a mutant TetR protein that binds to tetracycline-type antibiotics, allowing for controlled transcription and protein degradation, enabling precise regulation of target protein expression through the presence or absence of antibiotics like tetracycline.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transcription activator-inhibitor fusion protein system is used to control gene expression, then transcription can be controlled by tetracycline presence, but the control efficiency is insufficient and cytotoxicity occurs
Solution Approach 1:
The invention divides the control mechanism into two independent but coordinated systems: (1) a transcription control system using TetR-rtTA fusion protein that regulates mRNA synthesis, and (2) a protein stability control system using a degradation tag (such as PEST sequence or ubiquitin tag) that regulates protein degradation. This segmentation allows each system to operate optimally without the harmful effects of the other, achieving reliable control while reducing cytotoxicity.
Solution Approach 2:
The invention introduces an intermediary degradation tag sequence that mediates between the transcription control system and the protein expression system. This tag acts as a buffer that can be independently regulated, allowing the transcription system to control mRNA levels while the degradation tag controls protein half-life, thereby improving overall control efficiency and reducing cytotoxic effects.
2Reliability
If additional proteins like FKBP12 and rapamycin derivatives are used for degradation control, then protein stability can be controlled, but the system complexity increases and unknown side effects occur
Solution Approach 1:
The invention extracts and eliminates the need for additional auxiliary proteins like FKBP12 and rapamycin derivatives from the control system. Instead, it uses constitutively expressed cellular components (such as ubiquitin-proteasome system or PEST sequence recognition machinery) that are naturally present in the cell. This takes out the problematic external components while maintaining the desired protein stability control function.
Solution Approach 2:
The invention enables the cell's own intrinsic protein degradation machinery (ubiquitin-proteasome system, autophagy pathways, or PEST sequence recognition systems) to perform the degradation control function. The target protein is engineered with degradation tags that are recognized by these self-service cellular mechanisms, eliminating the need for external control proteins and reducing system complexity.
3Device complexity
If only transcription control is used, then the system is simple, but the control over protein expression levels is insufficient
Solution Approach 1:
The invention merges two control mechanisms into a unified system: transcriptional control (controlling mRNA synthesis rates) and post-transcriptional control (controlling protein degradation rates). By combining these two levels of regulation, the system achieves precise control over protein expression levels while maintaining relative simplicity through the use of constitutively expressed degradation machinery.
Solution Approach 2:
The invention changes the control parameters from solely transcriptional (mRNA synthesis rate) to include both transcriptional and proteolytic parameters (mRNA synthesis rate and protein degradation rate). This dual-parameter control allows for much more precise regulation of protein expression levels, enabling the system to achieve expression levels that were previously inaccessible with transcription control alone.
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 system provides stringent control over protein expression, improving induction efficiency by several hundred times compared to single-control methods, reducing cytotoxicity, and using safer, clinically validated tetracycline antibiotics for precise gene expression regulation.
Implementation Method 1
a mutant of a repressor protein, which binds to an antibiotic
Implementation Method 2
the degradation of the fusion protein, which is the expression product of the polynucleotide of (a), being controlled inside the cell by the presence or absence of an antibiotic inside the cell
Data Source
AI summary
The present invention provides an expression vector, containing expressibly (a) a polynucleotide encoding a fusion protein of a mutant of a repressor protein, which binds to an antibiotic, and a target protein, and (b) a polynucleotide encoding a protein controlling the transcription of the polynucleotide in (a), the transcription of the polynucleotide in (a) and the degradation of said fusion protein, which is the expression product of the polynucleotide in (a), being controlled inside a cell by the presence or absence of an antibiotic inside the cell.