Linear DNA With Phosphorothioate Adaptors for Exonuclease Resistance
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Solution Overview
Problem
Current methods for producing linear DNA products with enhanced resistance to nuclease digestion are limited, particularly in terms of flexibility and efficiency, as existing approaches either use phosphorothioated nucleotides or closed DNA molecules like plasmids or minicircles, which have limitations such as contamination, fidelity issues, and restricted utility in vivo.
Innovation Solution
A method involving the use of adaptor molecules, an endonuclease, and a ligase to form a single contiguous aqueous volume with a double-stranded DNA molecule, which generates a linear DNA product with enhanced resistance to nuclease digestion by appending the adaptor molecules to the ends of the DNA, potentially using phosphorothioated nucleotides and allowing for efficient production without the need for extensive purification steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phosphorothioated nucleotides are used to cap the ends of DNA, then resistance to exonuclease digestion is improved, but the complexity of the production process increases
Solution Approach 1:
The patent combines multiple steps (endonuclease digestion, adaptor ligation, and phosphorothioate incorporation) into a single one-pot reaction. The adaptor molecules contain pre-formed phosphorothioated nucleotides at their 5' ends, which are ligated directly to the DNA ends during the same reaction where endonuclease processes the DNA and ligase joins the adaptors. This eliminates separate purification and modification steps, reducing procedural complexity while maintaining exonuclease resistance.
Solution Approach 2:
The adaptor molecules serve as intermediaries that bridge the DNA ends and the phosphorothioate protection. Instead of directly modifying DNA ends with phosphorothioated nucleotides in a complex multi-step process, the patent uses adaptor molecules as mediators that already contain the protective phosphorothioated nucleotides. These adaptors are ligated to the DNA ends in a single reaction, providing exonuclease resistance through the intermediary adaptor structure.
2Reliability
If closed DNA molecules like plasmids are used, then resistance to nuclease digestion is improved, but contamination and fidelity issues increase
Solution Approach 1:
Instead of using traditional closed circular plasmids that require bacterial propagation (which introduces contamination and fidelity issues), the patent inverts the approach by creating closed linear DNA molecules. These are generated in vitro through one-pot reactions combining endonuclease digestion, adaptor ligation with phosphorothioated nucleotides, and DNA synthesis. The linear structure with covalently closed ends provides nuclease resistance without requiring bacterial culture, thereby eliminating contamination and maintaining sequence fidelity.
3Reliability
If multiple separate steps are used to produce linear DNA with nuclease resistance, then resistance to nuclease digestion is improved, but productivity decreases
Solution Approach 1:
The patent merges endonuclease digestion, adaptor ligation, and phosphorothioate incorporation into a single one-pot reaction that occurs simultaneously. The reaction mixture contains all necessary components: endonuclease to process DNA ends, ligase to join adaptors, and adaptor molecules with pre-formed phosphorothioated nucleotides. This consolidation eliminates multiple purification steps and separate reactions, dramatically improving productivity while ensuring the DNA ends are capped with exonuclease-resistant phosphorothioated nucleotides.
Solution Approach 2:
The one-pot reaction maintains continuous useful action throughout the process. As the endonuclease digests the DNA to create compatible ends, the ligase simultaneously joins the adaptor molecules to these ends, and the phosphorothioated nucleotides are incorporated continuously during ligation. This continuous multi-functional action eliminates idle time between steps and maximizes production efficiency while ensuring complete nuclease protection.
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 produces linear DNA products with prolonged resistance to exonuclease digestion, enabling efficient in vivo expression and reduced contamination, thus overcoming the limitations of existing techniques by providing a flexible and efficient means of producing nuclease-resistant DNA.
Implementation Method 1
contacting a double-stranded DNA molecule with an endonuclease, a ligase and first and second adaptor molecules
Implementation Method 2
contacting a double-stranded DNA molecule with an endonuclease, a ligase and first and second adaptor molecules to form a single contiguous aqueous volume
Implementation Method 3
Phosphorothioated nucleotides comprise a sulphur atom instead of a non-bridging oxygen atom. These modified nucleotides show comparable physical and chemical characteristics to corresponding unmodified nucleotides, but are resistant to exonuclease digestion.
Data Source
AI summary
Methods for producing a linear deoxyribonucleic acid (DNA) product with enhanced resistance to nuclease digestion are provided. The methods comprise: (a) contacting a double-stranded DNA molecule with an endonuclease, a ligase and first and second adaptor molecules to form a single contiguous aqueous volume; and (b) incubating the single contiguous aqueous volume to generate a linear DNA product. There are also provided linear deoxyribonucleic acid (DNA) products with enhanced resistance to nuclease digestion and uses thereof.