Programmable Transcription Factor Stability via Essential Gene Coupling
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Solution Overview
Problem
Existing programmable transcription factors face challenges in maintaining functionality across multiple generations due to mutations and unwanted silencing, leading to growth disadvantages or death in organisms, which can result in defective factors dominating populations.
Innovation Solution
A programmable transcription activator or repressor system is developed, where essential coding regions for viability are linked with promoters that require specific binding for expression, and non-essential regions can be controlled by the same promoter sequence, ensuring positive selection and maintaining functional transcription factor levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If programmable transcription factors are used to control gene expression, then transcriptional programming capability is improved, but mutations and unwanted silencing occur leading to loss of functionality over generations
Solution Approach 1:
The system performs preliminary action by linking the transcription factor's function to the essentiality of a coding region before genetic drift can occur. The promoter is designed to require the transcription factor for activation of an essential gene, creating a pre-established dependency that prevents loss-of-function mutations from persisting in the population.
Solution Approach 2:
The system implements feedback through positive selection: organisms that maintain functional transcription factors survive and reproduce because the essential coding region remains active, while those with mutations or silencing die off. This creates a feedback loop that continuously selects for and maintains transcription factor functionality across generations.
2Reliability
If essential coding regions are made dependent on programmable transcription factors, then positive selection for functional factors is achieved, but organism growth and reproduction are affected if factors are defective
Solution Approach 1:
The system converts the harmful effect of defective transcription factors (which would normally cause population decline) into a beneficial selection mechanism. By making the essential coding region dependent on the transcription factor, defective factors automatically lead to organism death, which purges the population of non-functional variants and ensures only organisms with working transcription factors survive and reproduce.
3Adaptability or versatility
If non-essential coding regions are controlled by the same promoter, then transcriptional control versatility is improved, but expression levels may interfere with cell growth and reproduction
Solution Approach 1:
The system applies local quality by differentiating the functional requirements of different coding regions. The essential coding region is placed under strict control requiring transcription factor binding for activation, while non-essential regions can be controlled by the same promoter but with different expression thresholds. This allows versatile transcriptional control while preventing harmful overexpression that would interfere with cell growth.
Data Source
AI summary
This disclosure describes a programmable transcription factor system. Generally, the system includes a programmable transcription factor, a polynucleotide that includes a coding region whose expression is either required or toxic for cell viability, and a promoter operably linked to the polynucleotide and having a binding site for the programmable transcription factor. The programmable transcription factor generally includes a domain that specifically binds to a promoter and a domain that either activates transcription (if the polynucleotide encodes an essential product) or represses transcription (if the polynucleotide encodes a toxic product).