Cell-Free Circular DNA Amplification Enzyme System
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for amplifying circular DNA are inefficient, requiring cell-based systems, linear DNA production, and primer-specific designs, limiting the size of amplified DNA to a few kilobases and necessitating additional cyclization steps.
Innovation Solution
A cell-free method involving a reaction mixture with specific enzyme groups that catalyze replication, Okazaki fragment maturation, and separation of sister circular DNAs under isothermal conditions, using enzymes such as DnaA, DNA polymerase III, and topoisomerase IV, allowing exponential amplification of circular DNA up to 200 kb or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If rolling circle amplification is used to amplify circular DNA in vitro, then amplification can be performed without cells, but a primer specific to the target DNA must be designed each time and additional cyclization steps are required
Solution Approach 1:
The invention enables circular DNA to autonomously replicate itself in vitro using purified cellular replication enzymes without requiring externally added primers or cyclization enzymes. The circular DNA template serves as both the template and the source of replication initiation, eliminating the need for primer design and additional cyclization steps.
Solution Approach 2:
The invention extracts the essential DNA replication function from living cells by using purified replication enzymes (DNA polymerase, helicase, primase, ligase) in a cell-free system. This extraction allows circular DNA amplification without the complexity of cell culture while maintaining the natural replication mechanism.
2Productivity
If conventional in vitro amplification methods are used, then amplification can be performed, but only linear DNA is produced requiring additional cyclization steps
Solution Approach 1:
The circular DNA template autonomously directs its own amplification and maintains its circular structure throughout the replication process. The purified ligase enzyme continuously seals nicks in the circular DNA, ensuring that amplification products remain circular without requiring separate cyclization steps.
Solution Approach 2:
The invention establishes a continuous replication cycle where circular DNA templates are repeatedly replicated and ligated in vitro. The system maintains circular DNA integrity throughout multiple replication cycles, continuously producing circular amplification products without interruption or additional processing steps.
3Reliability
If cell-based DNA cloning is used to amplify circular DNA, then high fidelity amplification is achieved, but troublesome procedures such as cell cultivation and extraction/purification are required
Solution Approach 1:
The invention extracts the DNA replication machinery from living cells, using purified replication enzymes in a cell-free system. This extraction eliminates the need for cell cultivation and DNA extraction procedures while maintaining the high fidelity of cellular replication through the use of accurate polymerases and proofreading mechanisms.
Solution Approach 2:
The invention replaces the complex mechanical system of cell-based cloning (cell culture, harvesting, lysis, purification) with a simplified biochemical system using purified enzymes. The cell-free system achieves the same replication fidelity without the cumbersome mechanical procedures of cell handling.
4Quantity of substance
If rolling circle amplification is used, then circular DNA can be amplified, but the amplification product is linear DNA requiring additional cyclization with recombinant enzymes
Solution Approach 1:
The circular DNA template continuously directs its own amplification and structural maintenance. The purified DNA ligase enzyme present in the replication system continuously seals nicks in the circular DNA strands, ensuring that all amplification products remain circular without requiring additional cyclization processing.
Solution Approach 2:
The invention merges the replication and cyclization functions into a single integrated process. The replication enzymes and ligase work together in one reaction system to simultaneously amplify and maintain the circular structure of DNA, eliminating the need for separate cyclization steps.
5Manufacturing precision
If minichromosome replication method is used, then circular DNA amplification is achieved, but only circular DNA of up to about 6 kbp can be amplified
Solution Approach 1:
The invention creates a universal amplification system using purified replication enzymes that can handle circular DNA of any size. The system is not limited to small minichromosomes but can amplify circular DNA ranging from small plasmids to large genomic circles, making it applicable to diverse DNA molecules regardless of size.
Solution Approach 2:
The invention changes the critical parameters of the replication system by using purified enzymes with optimized activities and concentrations. This allows the system to overcome the size limitations of minichromosome replication by adjusting enzyme parameters to handle larger DNA substrates efficiently.
6Productivity
If PCR is used for in vitro DNA amplification, then amplification can be performed, but circular DNA cannot be amplified as it is
Solution Approach 1:
The circular DNA template autonomously initiates and directs its own replication in the cell-free system without requiring external primers. The replication machinery recognizes the circular structure and initiates replication at appropriate sites, allowing circular DNA to serve itself as the template for amplification.
Solution Approach 2:
The invention establishes continuous replication cycles for circular DNA in vitro, where amplification products remain circular and can serve as templates for further replication. This continuous circular replication maintains the structural integrity and replicability of the DNA throughout the amplification 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
Enables easy, exponential amplification of long circular DNA without cells or plasmids, maintaining the circular structure and allowing specific amplification of ligated DNA fragments, with high fidelity and scalability.
Implementation Method 1
a first enzyme group that catalyzes replication of circular DNA
Implementation Method 2
a second enzyme group that catalyzes an Okazaki fragment maturation
Implementation Method 3
a third enzyme group that catalyzes a separation of two sister circular DNAs
Data Source
AI summary
The present invention provides a method for easily and exponentially amplifying circular DNA, particularly long chain circular DNA, in a cell-free system. Specifically, the present invention provides a method for amplifying circular DNA in which circular DNA having a replication origin sequence (origin of chromosome (oriC)) is mixed with a reaction solution containing the following enzyme groups to form a reaction mixture, which is then reacted under an isothermal condition, the enzyme groups being:(1) a first enzyme group that catalyzes replication of circular DNA;(2) a second enzyme group that catalyzes an Okazaki fragment maturation and synthesizes two sister circular DNAs constituting a catenane and(3) a third enzyme group that catalyzes a separation of two sister circular DNAs.