Plasmid Design for Minicircle Production via Sequential Enzyme Control
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Solution Overview
Problem
Current methods for producing minicircles, such as in vivo restriction systems, face challenges in achieving high yields and efficiently removing impurities like miniplasmids and parental plasmid sequences, making large-scale production difficult and prone to stability issues in bacterial producer strains.
Innovation Solution
A plasmid design comprising an endonuclease restriction site, a promoterless endonuclease expression cassette, a promoter, and recognition sequences for site-specific recombination, where the endonuclease expression is controlled after recombination, allowing for sequential recombination and restriction processes without additional induction steps, followed by affinity chromatography for purification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If in vivo restriction systems are used for minicircle production, then parental plasmid and miniplasmid can be degraded, but simultaneous expression of endonuclease and integrase leads to premature degradation of parental plasmid and reduced minicircle yield
Solution Approach 1:
The patent divides the expression control into separate regulatory elements: the integrase gene is under control of the P_BAD promoter, while the endonuclease gene is under control of a separate promoter (P_Lac or P_Tac). This segmentation allows independent temporal control of each enzyme's expression, preventing simultaneous expression that causes premature parental plasmid degradation while still enabling effective minicircle production when expressed in sequence.
Solution Approach 2:
The patent implements preliminary action by first expressing the integrase enzyme to catalyze recombination and generate minicircles from parental plasmid, and only after this recombination process is complete does the endonuclease expression begin to degrade the resulting miniplasmid. This sequential timing ensures that parental plasmid is not degraded before minicircle formation occurs.
2Reliability
If multiple copies of integrase and endonuclease are integrated into bacterial chromosome for in vivo restriction, then fewer contaminations can be achieved, but stability problems of producer strain occur due to redundant genomic information
Solution Approach 1:
The patent extracts the integrase and endonuclease genes from the bacterial chromosome and places them on a controllable plasmid vector system. This allows the genes to be present in sufficient copies for effective enzyme production while maintaining plasmid-based control mechanisms that prevent the stability issues associated with chromosomal integration of redundant genetic information.
Solution Approach 2:
The patent changes the regulatory parameters by using inducible promoters (P_BAD for integrase, P_Lac or P_Tac for endonuclease) that allow precise control of gene expression timing and levels. This parameter control enables sufficient enzyme production for effective purification while avoiding the uncontrolled expression that leads to producer strain instability.
3Reliability
If in vivo restriction approach is used with inducible promoter system, then miniplasmid and parental plasmid can be degraded, but change of pH and temperature during production makes large scale production difficult
Solution Approach 1:
The patent replaces the mechanical/physical approach of changing pH and temperature conditions with a biochemical control system using inducible promoters. Instead of altering environmental parameters to control enzyme expression, the system uses promoter-inducer interactions (arabinose for P_BAD, lactose or TCP for P_Lac/P_Tac) to control when and how much integrase and endonuclease are produced, maintaining stable cultivation conditions throughout the process.
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 enables high-yield production of minicircles with reduced impurities, facilitating efficient isolation and suitable for large-scale production by ensuring controlled expression and sequential processing of unwanted plasmid components.
Implementation Method 1
a sequence coding for an enzyme that catalyzes site-specific recombination, at least two recognition sequences for the enzyme that catalyzes site-specific recombination
Implementation Method 2
the endonuclease expression cassette is placed under control of the promoter only after recombination at the specific recognition sequences
Data Source
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AI summary
The present invention relates to a plasmid for minicircle production, a method for providing a minicircle and a minicircle produced by said method as well as a pharmaceutical composition comprising the same.