Covalently Closed dsDNA Assembly for Exonuclease-Resistant Vectors
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Solution Overview
Problem
Current viral and plasmid vectors used for gene therapy face issues such as immunogenicity and short-duration of expression, necessitating the development of more effective vector systems.
Innovation Solution
The assembly of covalently closed double stranded nucleic acids (ccDNA) is achieved through amplification with uracil-containing primers, followed by digestion using glycosylase and glycosylase-lyase to create loop structures, and subsequent ligation to form resistant vectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If viral or plasmid vectors are used for gene therapy, then gene delivery is achieved, but immunogenicity and short-duration of expression occur
Solution Approach 1:
The patent changes the structural parameters of the nucleic acid vector by creating covalently closed circular DNA through specific enzymatic processing. The method involves amplifying DNA with uracil-containing primers, digesting with glycosylase and glycosylase-lyase to create loop structures, and ligating to form closed circular molecules. This structural transformation eliminates linear ends that are susceptible to exonuclease degradation, thereby extending expression duration and improving vector stability without increasing immunogenicity.
2Ease of manufacture
If linear double stranded nucleic acid is used, then ease of assembly is achieved, but exonuclease degradation occurs
Solution Approach 1:
The patent applies preliminary action by incorporating uracil bases at the 5' ends of primers before amplification. These uracil bases serve as predetermined sites for subsequent enzymatic digestion. The glycosylase recognizes and removes these uracil bases, creating abasic sites that are then processed by glycosylase-lyase to generate loop structures. This preliminary placement of uracil sites enables controlled circularization while maintaining ease of assembly through standard PCR protocols.
Solution Approach 2:
The patent uses uracil bases as intermediary elements that facilitate the transformation from linear to circular structure. The uracil bases act as temporary markers that guide the enzymatic processing steps. After serving their mediating function in creating the loop structure, the uracil bases are removed, leaving the stable covalently closed circular DNA without requiring any residual intermediary elements in the final product.
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 method results in the generation of ccDNA vectors that are resistant to exonuclease degradation, providing improved delivery and expression of therapeutic genes.
Implementation Method 1
digesting the double stranded nucleic acid comprising one or more uracils at the 5′ end and the 3′ end using a glycosylase and a glycosylase-lyase to generate a double stranded nucleic acid comprising a loop structure
Implementation Method 2
the glycosylase-lyase breaks the phosphodiester backbone at a 3′ and 5′ sides of the abasic site
Implementation Method 3
ligating gaps in the double stranded nucleic acid comprising the loop structure at the 5′ end and the 3′ end using a ligase to generate the covalently closed double stranded nucleic acid
Data Source
AI summary
Provided herein are methods, systems, and compositions for assembly of covalently closed double stranded nucleic acids. Provided herein are methods, systems, and compositions for assembly covalently closed double stranded nucleic acids for use in various downstream processes.